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  • 1.
    Al-attar, N.
    et al.
    Iraq.
    Al-Shammari, R. M.
    Ireland.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rodriguez, B. J.
    Ireland.
    Rice, J. H.
    Ireland.
    Wide-field surface-enhanced Raman scattering from ferroelectrically defined Au nanoparticle microarrays for optical sensing2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    The acquisition-time in optical sensors using SERS is vital value. Wide-field SERS is used to perform high-density of hot-spots of GNPs photodeposition on a periodically-protonexchanged- LiNbO3 which, leads to increase the sensitivity at ultralow probe concentrations.

  • 2.
    Asadzadeh, Mohammad Zhian
    et al.
    Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria..
    Kock, Anton
    Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria..
    Popov, Maxim
    Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria..
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria.
    Spitaler, Juergen
    Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria..
    Romaner, Lorenz
    Mat Ctr Leoben Forsch GmbH MCL, Roseggerstr 12, A-8700 Leoben, Austria..
    Response modeling of single SnO2 nanowire gas sensors2019In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 295, p. 22-29Article in journal (Refereed)
    Abstract [en]

    The response of single SnO2 nanowire gas sensors with different diameters between 20 and 140 nm are evaluated by calculating the nanowire conductivity as a function of the surface charge density. The procedure involves the numerical solution of the Poisson-Boltzmann equation for the electrostatic potential in cylindrical geometry in order to model the depletion region and band bending at the SnO2 nanowire surface. In the model we take into account varying surface charge densities sigma and bulk electron concentrations n(0) to calculate the electrical conductivity. Considering the fact that the surface charge density depends on the nanowire surface interactions with ambient gas, the model allows us to simulate the sensor response when the nanowire is employed as gas sensing component. We report a saturation in depletion length lambda versus surface charge density s which is the principal reason for limiting the sensor responses. The results also show that the conductivity is decreasing by increasing surface charge density, the smaller the nanowire diameter the steeper the decrease. As a result the nanowire response is proportional to 1/d where d is the nanowire diameter. Furthermore, we argue about the validity of the modeling results and their relevance to experimental findings on SnO2 nanowire based gas sensors reported in literature.

  • 3.
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Integrated Nanophotonic Devices in Lithium Niobate2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lithium niobate (LN) is a ferroelectric crystal offering a broad transparency spectrum, together with excellent electro-optic and nonlinear optical properties. Thanks to them, LN is setting the standard for quantum optics and telecommunications in critical applications such as ultrafast modulation and frequency conversion. The development of a reliable nanophotonic platform in LN can be expected to effectively leverage all such appealing functionalities in compact and integrated formats and provide important and complementary functionalities to current silicon-photonics platforms.

    This thesis encompasses systematic and consistent efforts with the goal to achieve the key building blocks for a comprehensive integrated nanophotonic platform in LN. It involves work on the technology side, sustained and complemented by modelling and experiments, ultimately leading to the demonstration of a few novel devices.

    Ultrahigh field confinement in nanophotonic waveguides is accompanied by the appearance of non-negligible longitudinal components in the guided optical fields. By fabricating high-quality LN nanopillars and analyzing with theory and experiments their second harmonic generation (SHG) response, we provide evidence for the existence of longitudinal field components and demonstrate the possibility to reshape the SHG polar emission properties of these submicrometric waveguides by fine-tuning the nanopillar size.

    This thesis also presents a different technological approach, allowing the fabrication of photonic wires as small as 250 nm with lengths up to 1 cm on LN-on-insulator (LNOI), suitable for upscaling to photonic integrated circuit (PIC) architectures. By optimizing the fabrication process, the propagation losses of single-mode waveguides at telecom wavelengths on this platform were brought down from 76 to 1.13 dB/cm. Fine-pitch waveguide structuring was also successfully achieved, enabling LNOI-to-fiber grating couplers and waveguide Bragg gratings, the latter featuring record extinction ratios in LNOI (45 dB), comparable to the state of the art in silicon.

    The thesis involves also theoretical work on the design of photonic wires where the interplay between LN and waveguide birefringence is used to achieve polarization-insensitive operation for the fundamental guided modes.

    Finally, two demonstrators are provided for novel and emerging applications of LN to the life sciences, using LNOI surface-patterned templates for enhanced Raman spectroscopy and LN templates for controlled neuron growth and manipulation in microfluidic environments, respectively.

  • 4.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Schollhammer, Jean
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gylfason, Kristinn B
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Bragg gratings in thin-film LiNbO3 waveguides2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Optics Express, ISSN 1094-4087, Vol. 25, no 26, p. 32323-32332Article in journal (Refereed)
    Abstract [en]

    We design, fabricate and characterize sidewall corrugated Bragg gratings in a high confinement integrated optics lithium niobate platform, comprising submicrometric photonic wires, tapers and grating couplers to interface off-chip standard telecom optical fibers. We analyze the grating performance as band-rejection filter for TE-polarized signals in the telecom C-band, considering both rectangular and sinusoidal sidewall profiles, and demonstrate record extinction ratios as high as 27 dB and rejection bandwidths as narrow as 3 nm. The results show the potential for an efficient integration of novel photonic functionalities into low-footprint LiNbO3 nonlinear and electro-optical waveguide devices.

  • 5.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Second-Harmonic generation engineering in lithium niobate nanopillars2019In: Proceedings 2015 European Conference on Lasers and Electro-Optics - European Quantum Electronics Conference, CLEO/Europe-EQEC 2015, Optical Society of America (OSA) , 2019Conference paper (Refereed)
  • 6.
    Bergstrand, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Super resolution fluorescence imaging: analyses, simulations and applications2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fluorescence methods offer extraordinary sensitivity and specificity, and are extensively used in the life sciences. In recent years, super resolution fluorescence imaging techniques have developed strongly, uniquely combining ~10 nm sub diffraction resolution and specific labeling with high efficiency. This thesis explores this potential, with a major focus on Stimulated Emission Depletion, STED, microscopy, applications thereof, image analyses and simulation studies. An additional theme in this thesis is development and use of single molecule fluorescence correlation spectroscopy, FCS, and related techniques, as tools to study dynamic processes at the molecular level. In paper I the proteins cytochrome-bo3 and ATP-synthase are studied with fluorescence cross-correlation spectroscopy, FCCS. These two proteins are a part of the energy conversion process in E. coli, converting ADP into ATP. We found that an increased interaction between these proteins, detected by FCCS, correlates with an increase in the ATP production. In paper II an FCS-based imaging method is developed, capable to determine absolute sizes of objects, smaller than the resolution limit of the microscope used. Combined with STED, this may open for studies of membrane nano-domains, such as those investigated by simulations in paper VII. In paper III and paper IV super resolution STED imaging was applied on Streptococcus Pneumoniae, revealing information about function and distribution of proteins involved in the defense mechanism of the bacteria, as well as their role in bacterial meningitis. In paper V, we used STED imaging to investigate protein distributions in platelets. We then found that the adhesion protein P-selectin changes its distribution pattern in platelets incubated with tumor cells, and with machine learning algorithms and classical image analysis of the STED images it is possible to automatically distinguish such platelets from platelets activated by other means. This could provide a strategy for minimally invasive diagnostics of early cancer development, and deeper understanding of the role of platelets in cancer development. Finally, this thesis presents Monte-Carlo simulations of biological processes and their monitoring by FCS. In paper VI, a combination of FCCS and simulations was applied to resolve the interactions between a transcription factor (p53) and an oncoprotein (MDM2) inside live cells. In paper VII, the feasibility of FCS techniques for studying nano-domains in membranes is investigated purely by simulations, identifying the conditions under which such nano-domains would be possible to detect by FCS. In paper VIII, proton exchange dynamics at biological membranes were simulated in a model, verifying experimental FCS data and identifying fundamental mechanisms by which membranes mediate proton exchange on a local (~10nm) scale.

  • 7.
    Bergstrand, Jan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Liu, Qingyun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Huang, Bingru
    Würth, Christian
    Resch-Genger, Ute
    Zhan, Qiuqiang
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Liu, Haichun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    On the decay time of upconversion luminescence2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 11, p. 4959-4969Article in journal (Refereed)
    Abstract [en]

    In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.

  • 8.
    Bergstrand, Jan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Xu, Lei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Albanova Univ Ctr, Expt Biomol Phys, SE-10691 Stockholm, Sweden..
    Miao, Xinyan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Albanova Univ Ctr, Expt Biomol Phys, SE-10691 Stockholm, Sweden..
    Li, Nailin
    Karolinska Inst, Dept Med Solna, Karolinska Univ Hosp Solna, Clin Pharmacol, L7 03, SE-17176 Stockholm, Sweden..
    Öktem, Ozan
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Franzen, Bo
    Karolinska Inst, Dept Oncol Pathol, Karolinska Univ Hosp, K7,Z1 00, S-17176 Stockholm, Sweden..
    Auer, Gert
    Karolinska Inst, Dept Oncol Pathol, Karolinska Univ Hosp, K7,Z1 00, S-17176 Stockholm, Sweden..
    Lomnytska, Marta
    Karolinska Inst, Dept Oncol Pathol, Karolinska Univ Hosp, K7,Z1 00, S-17176 Stockholm, Sweden.;Acad Univ Hosp, Dept Obstet & Gynaecol, SE-75185 Uppsala, Sweden.;Uppsala Univ, Inst Women & Child Hlth, SE-75185 Uppsala, Sweden..
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Super-resolution microscopy can identify specific protein distribution patterns in platelets incubated with cancer cells2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 20, p. 10023-10033Article in journal (Refereed)
    Abstract [en]

    Protein contents in platelets are frequently changed upon tumor development and metastasis. However, how cancer cells can influence protein-selective redistribution and release within platelets, thereby promoting tumor development, remains largely elusive. With fluorescence-based super-resolution stimulated emission depletion (STED) imaging we reveal how specific proteins, implicated in tumor progression and metastasis, re-distribute within platelets, when subject to soluble activators (thrombin, adenosine diphosphate and thromboxane A2), and when incubated with cancer (MCF-7, MDA-MB-231, EFO21) or non-cancer cells (184A1, MCF10A). Upon cancer cell incubation, the cell-adhesion protein P-selectin was found to re-distribute into circular nano-structures, consistent with accumulation into the membrane of protein-storing alpha-granules within the platelets. These changes were to a significantly lesser extent, if at all, found in platelets incubated with normal cells, or in platelets subject to soluble platelet activators. From these patterns, we developed a classification procedure, whereby platelets exposed to cancer cells, to non-cancer cells, soluble activators, as well as non-activated platelets all could be identified in an automatic, objective manner. We demonstrate that STED imaging, in contrast to electron and confocal microscopy, has the necessary spatial resolution and labelling efficiency to identify protein distribution patterns in platelets and can resolve how they specifically change upon different activations. Combined with image analyses of specific protein distribution patterns within the platelets, STED imaging can thus have a role in future platelet-based cancer diagnostics and therapeutic monitoring. The presented approach can also bring further clarity into fundamental mechanisms for cancer cell-platelet interactions, and into non-contact cell-to-cell interactions in general.

  • 9.
    Bergstrand, Jan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Xu, Lei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Miao, Xinyan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Li, Nailin
    Karolinska Institutet, Department of Medicine, Karolinska University Hospital, L7:03, SE-171 76 Stockholm, Sweden.
    Öktem, Ozan
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Franzén, Bo
    Karolinska Institutet, Department of Medicine, Karolinska University Hospital, L7:03, SE-171 76 Stockholm, Sweden.
    Auer, Gert
    Karolinska Institutet, Department of Medicine, Karolinska University Hospital, L7:03, SE-171 76 Stockholm, Sweden.
    Lomnytska, Marta
    Karolinska Institutet, Department of Medicine, Karolinska University Hospital, L7:03, SE-171 76 Stockholm, Sweden.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Super-resolution microscopy can identify specific protein distribution patterns in platelets incubated with cancer cellsManuscript (preprint) (Other academic)
    Abstract [en]

    Protein contents in platelets are frequently changed upon tumor development and metastasis. However, how cancer cells can influence protein-selective redistribution and release within platelets, thereby promoting tumor development, remains largely elusive. With fluorescence-based super-resolution stimulated emission depletion (STED) imaging we reveal how specific proteins, implicated in tumor progression and metastasis, re-distribute within platelets, when subject to soluble activators (thrombin, adenosine-diphosphate and thromboxaneA2), and when incubated with cancer (MCF-7, MDA-MB-231, EFO21) or non-cancer cells (184A1, MCF10A). Upon cancer cell incubation, the cell-adhesion protein P-selectin was found to re-distribute into circular nano-structures, consistent with accumulation into the membrane of protein-storing alpha-granules within the platelets. These changes were to a significantly lesser extent, if at all, found in platelets incubated with normal cells, or in platelets subject to soluble platelet activators. From these patterns, we developed a classification procedure, whereby platelets exposed to cancer cells, to non-cancer cells, soluble activators as well as non-activated platelets all could be identified in an automatic, objective manner. We demonstrate that STED imaging, in contrast to electron and confocal microscopy, has the necessary spatial resolution and labelling efficiency to identify protein distribution patterns in platelets and can resolve how they specifically change upon different activations. Combined with image analyses of specific protein distribution patterns within the platelets, STED imaging can thus have a role in future platelet-based cancer diagnostics and therapeutic monitoring. The presented approach can also bring further clarity into fundamental mechanisms for cancer cell-platelet interactions, and into non-contact cell-to-cell interactions in general. 

  • 10.
    Brambilla, E.
    et al.
    Univ Insubria, Dept Sci & High Technol, Via Valleggio 11, I-22100 Como, Italy..
    Jedrkiewicz, O.
    CNR, Ist Foton & Nanotecnol, Udr Como, Via Valleggio 11, I-22100 Como, Italy..
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Tamosauskas, G.
    Vilnius Univ, Dept Quantum Elect, Sauletekio 10, LT-10223 Vilnius, Lithuania..
    Gatti, A.
    CNR, Ist Foton & Nanotecnol, Udr Como, Via Valleggio 11, I-22100 Como, Italy..
    Three and Four-Modes Parametric Processes in Hexagonally Poled Nonlinear Photonic Crystals2018In: OPTICS, PHOTONICS AND LASERS / [ed] Yurish, S Y, INT FREQUENCY SENSOR ASSOC-IFSA , 2018, p. 176-178Conference paper (Refereed)
    Abstract [en]

    We investigate the properties of the field emitted through parametric down-conversion (PDC) in a nonlinear photonics crystal (NPC) with a hexagonal poling pattern, both from a theoretical point of view and with an experiment performed at the University of Insubria. Considering the high gain regime of PDC, we demonstrate the existence of concurrent PDC processes mediated by two noncollinear poling vectors which are coherently coupled and reciprocally stimulated. We find that these non-standard 3-mode and 4-mode interaction processes undergo a substantial enhancement of the parametric gain with respect to the usual 2-mode PDC, and give rise to hot spots order of magnitudes brighter than standard 2-mode fluorescence which have been observed in the source far field. We performed a complete characterization of the source spectral-angular emission, finding a very good agreement between the experiment and the theoretical predictions.

  • 11.
    Brodu, Annalisa
    et al.
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Ballottin, Mariana V.
    Radboud Univ Nijmegen, High Field Magnet Lab, HFML EMFL, NL-6525 ED Nijmegen, Netherlands..
    Buhot, Jonathan
    Radboud Univ Nijmegen, High Field Magnet Lab, HFML EMFL, NL-6525 ED Nijmegen, Netherlands..
    van Harten, Elleke J.
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Dupont, Dorian
    Univ Ghent, Phys & Chem Nanostruct, B-9000 Ghent, Belgium..
    La Porta, Andrea
    Univ Antwerp, EMAT, Electron Microscopy Mat Res, B-2020 Antwerp, Belgium..
    Prins, P. Tim
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Tessier, Mickael D.
    Univ Ghent, Phys & Chem Nanostruct, B-9000 Ghent, Belgium..
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Bals, Sara
    Univ Antwerp, EMAT, Electron Microscopy Mat Res, B-2020 Antwerp, Belgium..
    Hens, Zeger
    Univ Ghent, Phys & Chem Nanostruct, B-9000 Ghent, Belgium..
    Rabouw, Freddy T.
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Christianen, Peter C. M.
    Radboud Univ Nijmegen, High Field Magnet Lab, HFML EMFL, NL-6525 ED Nijmegen, Netherlands..
    Donega, Celso de Mello
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Vanmaekelbergh, Daniel
    Univ Utrecht, Debye Inst Nanomat Sci, NL-3584 CC Utrecht, Netherlands..
    Exciton Fine Structure and Lattice Dynamics in InP/ZnSe Core/Shell Quantum Dots2018In: ACS Photonics, E-ISSN 2330-4022, Vol. 5, no 8, p. 3353-3362Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline InP quantum dots (QDs) hold promise for heavy-metal-free optoelectronic applications due to their bright and size tunable emission in the visible range. Photochemical stability and high photoluminescence (PL) quantum yield are obtained by a diversity of epitaxial shells around the InP core. To understand and optimize the emission line shapes, the exciton fine structure of InP core/shell QD systems needs be investigated. Here, we study the exciton fine structure of InP/ZnSe core/shell QDs with core diameters ranging from 2.9 to 3.6 nm (PL peak from 2.3 to 1.95 eV at 4 K). PL decay measurements as a function of temperature in the 10 mK to 300 K range show that the lowest exciton fine structure state is a dark state, from which radiative recombination is assisted by coupling to confined acoustic phonons with energies ranging from 4 to 7 meV, depending on the core diameter. Circularly polarized fluorescence line-narrowing (FLN) spectroscopy at 4 K under high magnetic fields (up to 30 T) demonstrates that radiative recombination from the dark F = +/- 2 state involves acoustic and optical phonons, from both the InP core and the ZnSe shell. Our data indicate that the highest intensity FLN peak is an acoustic phonon replica rather than a zero-phonon line, implying that the energy separation observed between the F = +/- 1 state and the highest intensity peak in the FLN spectra (6 to 16 meV, depending on the InP core size) is larger than the splitting between the dark and bright fine structure exciton states.

  • 12. Cheng, Y.
    et al.
    Chi, X.
    Gu, C.
    Zou, K.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Chen, S.
    Liu, H.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, X.
    Experimental demonstration of superconducting nanowire single-photon detectors integrated with current reservoirs2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate the superconducting nanowire single-photon detectors integrated with current reservoirs that function as low-noise pre-amplifiers to increase the signal-to-noise ratio of detectors' outputs.

  • 13.
    Chi, Xiaoming
    et al.
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Zou, Kai
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Gu, Chao
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Cheng, Yuhao
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Hu, Nan
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Lan, Xiaojian
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Chen, Shufan
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Lin, Zuzeng
    KTH, School of Engineering Sciences (SCI), Applied Physics. Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, Xiaolong
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Fractal superconducting nanowire single-photon detectors with reduced polarization sensitivity2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 20, p. 5017-5020Article in journal (Refereed)
    Abstract [en]

    We demonstrate superconducting nanowire single-photon detectors (SNSPDs) based on a fractal design of the nanowires to reduce the polarization sensitivity of detection efficiency. We patterned niobium titanium nitride thin films into Peano curves with a linewidth of 100 nm and integrated the nanowires with optical microcavities to enhance their optical absorption. At a base temperature of 2.6 K, the fractal SNSPD exhibited a polarization-maximum device efficiency of 67% and a polarization-minimum device efficiency of 61% at a wavelength of 1550 nm. Therefore, the polarization sensitivity, defined as their ratio, was 1.1, lower than the polarization sensitivity of the SNSPDs in the meander design. The reduced polarization sensitivity of the detector could be maintained for higher-order spatial modes in multimode optical fibers and could tolerate misalignment between the optical mode and the detector. This fractal design is applicable to both amorphous and polycrystalline materials that are commonly used for making SNSPDs.

  • 14.
    De Luca, Eleonora
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallium indium phosphide nanostructures with suppressed photoluminescence for applications in nonlinear optics2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    Nanostructured GaInP shows remarkable second-order nonlinear properties. By measuring the second harmonic generation before and after stimulating intrinsic photobleaching, we observed suppressed photoluminescence and unchanged nonlinear properties, making it suitable for low-noise applications. 

  • 15.
    Elshaari, Ali W.
    et al.
    Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Buyukozer, Efe
    Swiss Fed Inst Technol, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Zadeh, Iman Esmaeil
    Delft Univ Technol, Opt Grp, NL-2628 CJ Delft, Netherlands..
    Lettner, Thomas
    Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Zhao, Peng
    Tsinghua Univ, Tsinghua Natl Lab Informat Sci & Technol, Dept Elect Engn, Beijing, Peoples R China..
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Reimer, Michael E.
    Univ Waterloo, Inst Quantum Comp, Waterloo, ON N2L 3G1, Canada.;Univ Waterloo, Dept Elect & Comp Engn, Waterloo, ON N2L 3G1, Canada..
    Dalacu, Dan
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Poole, Philip J.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Strain-Tunable Quantum Integrated Photonics2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 12, p. 7969-7976Article in journal (Refereed)
    Abstract [en]

    Semiconductor quantum dots are crucial parts of the photonic quantum technology toolbox because they show excellent single-photon emission properties in addition to their potential as solid-state qubits. Recently, there has been an increasing effort to deterministically integrate single semiconductor quantum dots into complex photonic circuits. Despite rapid progress in the field, it remains challenging to manipulate the optical properties of waveguide-integrated quantum emitters in a deterministic, reversible, and nonintrusive manner. Here we demonstrate a new class of hybrid quantum photonic circuits combining III V semiconductors, silicon nitride, and piezoelectric crystals. Using a combination of bottom-up, top-down, and nanomanipulation techniques, we realize strain tuning of a selected, waveguide-integrated, quantum emitter and a planar integrated optical resonator. Our findings are an important step toward realizing reconfigurable quantum-integrated photonics, with full control over the quantum sources and the photonic circuit.

  • 16.
    Fognini, A.
    et al.
    Delft Univ Technol, Kavli Inst Nanosci Delft, NL-2628 CJ Delft, Netherlands. hmadi, A..
    Ahmadi, A.
    Zeeshan, M.
    Fokkens, J. T.
    Gibson, S. J.
    Sherlekar, N.
    Daley, S. J.
    Dalacu, D.
    Poole, P. J.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reimer, M. E.
    Dephasing Free Photon Entanglement with a Quantum Dot2019In: ACS Photonics, E-ISSN 2330-4022, Vol. 6, no 7, p. 1656-1663Article in journal (Refereed)
    Abstract [en]

    Generation of photon pairs from quantum dots with near-unity entanglement fidelity has been a long-standing scientific challenge. It is generally thought that the nuclear spins limit the entanglement fidelity through spin flip dephasing processes. However, this assumption lacks experimental support. Here, we show two-photon entanglement with negligible dephasing from an indium rich single quantum dot comprising a nuclear spin of 9/2 when excited quasi-resonantly. This finding is based on a significantly close match between our entanglement measurements and our model that assumes no dephasing and takes into account the detection system's timing jitter and dark counts. We suggest that neglecting the detection system is responsible for the degradation of the measured entanglement fidelity in the past and not the nuclear spins. Therefore, the key to unity entanglement from quantum dots comprises a resonant excitation scheme and a detection system with ultralow timing jitter and dark counts.

  • 17.
    Garcia-Guirado, Jose
    et al.
    Barcelona Inst Sci & Technol, ICFO Inst Ciencies Foton, Barcelona 08860, Spain..
    Svedendahl, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Barcelona Inst Sci & Technol, ICFO Inst Ciencies Foton, Barcelona 08860, Spain.
    Puigdollers, Joaquim
    Univ Politecn Cataluna, Dept Engn Elect, ES-08034 Barcelona, Spain..
    Quidantt, Romain
    Barcelona Inst Sci & Technol, ICFO Inst Ciencies Foton, Barcelona 08860, Spain.;ICREA, Barcelona 08010, Spain..
    Enantiomer-Selective Molecular Sensing Using Racemic Nanoplasmonic Arrays2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 10, p. 6279-6285Article in journal (Refereed)
    Abstract [en]

    Building blocks of life show well-defined chiral symmetry which has a direct influence on their properties and role in Nature. Chiral molecules are typically characterized by optical techniques such as circular dichroism (CD) where they exhibit signatures in the ultraviolet frequency region. Plasmonic nanostructures have the potential to enhance the sensitivity of chiral detection and translate the molecular chirality to the visible spectral range. Despite recent progress, to date, it remains unclear which properties plasmonic sensors should exhibit to maximize this effect and apply it to reliable enantiomer discrimination. Here, we bring further insight into this complex problem and present a chiral plasmonic sensor composed of a racemic mixture of gammadions with no intrinsic CD, but high optical chirality and electric field enhancements in the near-fields. Owing to its unique set of properties, this configuration enables us to directly differentiate phenylalanine enantiomers in the visible frequency range.

  • 18.
    Gatti, Alessandra
    et al.
    CNR, Ist Foton & Nanotecnol, Piazza Leonardo Da Vinci 32, Milan, Italy.;Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Brambilla, Enrico
    Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jedrkiewicz, Ottavia
    CNR, Ist Foton & Nanotecnol, Piazza Leonardo Da Vinci 32, Milan, Italy.;Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Golden ratio entanglement in hexagonally poled nonlinear crystals2018In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 98, no 5, article id 053827Article in journal (Refereed)
    Abstract [en]

    This work analyzes the quantum state of twin photons and twin beams generated by parametric down-conversion in a hexagonally poled photonic crystal, characterized by the simultaneous presence of two nonlinear processes sustained by two vectors of the reciprocal lattice. In those special points of the fluorescence spectrum where the two processes coexist, we show that a tripartite entangled state is realized, equivalent to a single parametric process followed by a beam splitter. By proper angle tuning, a peculiar resonance condition is reached, with a transition to a four-mode entanglement, dominated by the golden ratio of the segment phi = (1 + root 5)/2. A maximal coherence between the two nonlinear processes is established here, as the overall process is shown to be equivalent to two independent parametric processes followed by a beam splitter. We offer an interpretation of the occurrence of the golden ratio in this system based on an analogy between the evolution of the light modes and the Fibonacci sequence.

  • 19.
    Gourgues, Ronan
    et al.
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Zadeh, Iman Esmaeil
    Single Quantum BV, NL-2628 CH Delft, Netherlands.;Delft Univ Technol, ImPhys Dept, Opt Res Grp, Fac Appl Sci, Lorentzweg 1, NL-2628 CJ Delft, Netherlands..
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bulgarini, Gabriele
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Los, Johannes W. N.
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Dalacu, Dan
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Poole, Philip J.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Dorenbos, Sander N.
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Controlled integration of selected detectors and emitters in photonic integrated circuits2019In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, no 3, p. 3710-3716Article in journal (Refereed)
    Abstract [en]

    Integration of superconducting nanowire single-photon detectors and quantum sources with photonic waveguides is crucial for realizing advanced quantum integrated circuits. However, scalability is hindered by stringent requirements on high-performance detectors. Here we overcome the yield limitation by controlled coupling of photonic channels to pre-selected detectors based on measuring critical current, timing resolution, and detection efficiency. As a proof of concept of our approach, we demonstrate a hybrid on-chip full-transceiver consisting of a deterministically integrated detector coupled to a selected nanowire quantum dot through a filtering circuit made of a silicon nitride waveguide and a ring resonator filter, delivering 100 dB suppression of the excitation laser. In addition, we perform extensive testing of the detectors before and after integration in the photonic circuit and show that the high performance of the superconducting nanowire detectors, including timing jitter down to 23 +/- 3 ps, is maintained. Our approach is fully compatible with wafer-level automated testing in a cleanroom environment. 

  • 20.
    Gu, C.
    et al.
    China.
    Chi, X.
    China.
    Cheng, Y.
    China.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, N.
    China.
    Lan, X.
    Chona.
    Zou, K.
    China.
    Chen, S.
    China.
    Lin, Z.
    China.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, X.
    China.
    Fractal superconducting nanowire single-photon detectors with low polarization sensitivity2018In: Optics InfoBase Conference Papers, Optical Society of America, 2018Conference paper (Refereed)
    Abstract [en]

    We demonstrated a fractal superconducting nanowire single-photon detector and achieved 42% device efficiency and 1.04 polarization sensitivity. The low polarization sensitivity can be maintained for higher-order spatial modes in few-mode optical fibers.

  • 21. Gu, C.
    et al.
    Chi, X.
    Cheng, Y.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, N.
    Lan, X.
    Zou, K.
    Chen, S.
    Lin, Zuzeng
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hu, X.
    Fractal superconducting nanowire single-photon detectors with low polarization sensitivity2018In: 2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8426796Conference paper (Refereed)
    Abstract [en]

    We demonstrated a fractal superconducting nanowire single-photon detector and achieved 42% device efficiency and 1.04 polarization sensitivity. The low polarization sensitivity can be maintained for higher-order spatial modes in few-mode optical fibers.

  • 22. Hu, Xiaolong
    et al.
    Hu, Nan
    Meng, Yun
    Zou, Kai
    Xu, Liang
    Lan, Xiaojian
    Chi, Xiaoming
    Gu, Chao
    Cheng, Yuhao
    Wu, Hao
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Superconducting nanowire single-photon detectors at the infrared spectrum range: detection efficiency and timing jitter2019In: TERAHERTZ, RF, MILLIMETER, AND SUBMILLIMETER-WAVE TECHNOLOGY AND APPLICATIONS XII / [ed] Sadwick, LP Yang, T, 2019Conference paper (Refereed)
    Abstract [en]

    This paper reviews some recent research progress in superconducting nanowire single-photon detectors (SNSPDs) at the infrared spectrum range, with particular emphasis on detection efficiency and timing jitter. For detection efficiency, we present fractal SNSPDs with reduced polarization sensitivity; for timing jitter, we present two mechanisms of device timing jitter - vortex-crossing-induced timing jitter and spatial-inhomogeneity-induced timing jitter.

  • 23.
    Jöns, Klaus D.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Dalacu, D.
    Poole, P. J.
    Gulinatti, A.
    Giudice, A.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reimer, M. E.
    Erratum to: Bright nanoscale source of deterministic entangled photon pairs violating Bell’s inequality (Scientific Reports, (2017), 7, 1, (1700), 10.1038/s41598-017-01509-6)2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 7751Article in journal (Refereed)
  • 24. Kilinc, D
    et al.
    Blasiak, A
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Carville, N. C.
    Al-Adli, A.
    Al-Shammari, R. M.
    Rice, J. H.
    Lee, G. U.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rodriguez, B. J.
    Charge and topography patterned lithium niobate provides physical cues to fluidically isolated cortical axons2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 5, article id 053702Article in journal (Refereed)
    Abstract [en]

    In vitro devices that combine chemotactic and physical cues are needed for understanding how cells integrate different stimuli. We explored the suitability of lithium niobate (LiNbO3), a transparent ferroelectric material that can be patterned with electrical charge domains and micro/ nanotopography, as a neural substrate. On flat LiNbO3 z-surfaces with periodically alternating charge domains, cortical axons are partially aligned with domain boundaries. On submicron-deep etched trenches, neurites are aligned with the edges of the topographical features. Finally, we bonded a bicompartmental microfluidic chip to LiNbO3 surfaces patterned by etching, to create isolated axon microenvironments with predefined topographical cues. LiNbO3 is shown to be an emerging neuron culture substrate with tunable electrical and topographical properties that can be integrated with microfluidic devices, suitable for studying axon growth and guidance mechanisms under combined topographical/chemical stimuli.

  • 25.
    Koeck, A.
    et al.
    Mat Ctr Leoben Forsch GmbH, A-8700 Leoben, Austria..
    Deluca, M.
    Mat Ctr Leoben Forsch GmbH, A-8700 Leoben, Austria..
    Sosada-Ludwikowska, F.
    Mat Ctr Leoben Forsch GmbH, A-8700 Leoben, Austria..
    Wimmer-Teubenbacher, R.
    Mat Ctr Leoben Forsch GmbH, A-8700 Leoben, Austria..
    Lackner, E.
    Ams AG, A-8140 Premstatten, Austria..
    Rohracher, K.
    Ams AG, A-8140 Premstatten, Austria..
    Wachmann, E.
    Ams AG, A-8140 Premstatten, Austria..
    Niehaus, J. S.
    Fraunhofer Inst Appl Polymer Res, IAP CAN, D-14476 Potsdam, Germany..
    Becker, S.
    Fraunhofer Inst Appl Polymer Res, IAP CAN, D-14476 Potsdam, Germany..
    Tokmak, Oe.
    Fraunhofer Inst Appl Polymer Res, IAP CAN, D-14476 Potsdam, Germany..
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Sowwan, M.
    Okinawa Inst Sci & Technol, Grad Univ, Okinawa, Japan..
    Singh, V.
    Okinawa Inst Sci & Technol, Grad Univ, Okinawa, Japan..
    Multifunctional Nanoparticles - Key for Optimizing Chemical Nanosensors2018In: ASDAM 2018 - Proceedings: 12th International Conference on Advanced Semiconductor Devices and Microsystems / [ed] Breza, J Donoval, D Vavrinsky, E, IEEE, 2018, p. 227-231, article id 8544608Conference paper (Refereed)
    Abstract [en]

    Multifunctional nanoparticles are key for optimizing the performance of chemical sensor devices. We have fabricated a variety of nanosensor devices based on ultrathin metal oxide films and nanowires, which have been integrated on CMOS-based micro-hotplate chips. These sensors have been functionalized with metallic as well as bimetallic nanoparticles. We have demonstrated that Pt-NPs or NiPt-NPs, strongly increase the sensitivity to carbon monoxide and supress the cross selectivity to humidity in case of SnO2 thin film based devices. We have employed both nanoparticles synthesized in solution, which are ink-jet deposited, as well as nanoparticles, which are implemented by gas phase synthesis directly on the micro-hotplate chips. The Pt-functionalized SnO2-thin film sensors show a strongly increased response to CO, which is almost independent of humidity as compared to the bare SnO2-thin film sensor. The highest response of more than 90% has been achieved with NiPt-functionalized SnO2-thin film sensors at a very low operation temperature of only 150 degrees C.

  • 26.
    Machhadani, Houssaine
    et al.
    Univ Grenoble Alpes, CEA INAC PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Bougerol, Catherine
    Univ Grenoble Alpes, CNRS Inst Neel, 25 Av Martyrs, F-38000 Grenoble, France..
    Lequien, Stephane
    Univ Grenoble Alpes, CEA INAC MEM, 17 Av Martyrs, F-38000 Grenoble, France..
    Thomassin, Jean-Luc
    Univ Grenoble Alpes, CEA INAC PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Mollard, Nicolas
    Univ Grenoble Alpes, CEA INAC MEM, 17 Av Martyrs, F-38000 Grenoble, France..
    Mukhtarova, Anna
    Univ Grenoble Alpes, CEA INAC PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gerard, Jean-Michel
    Univ Grenoble Alpes, CEA INAC PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Monroy, Eva
    Univ Grenoble Alpes, CEA INAC PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Improvement of the critical temperature of NbTiN films on III-nitride substrates2019In: Superconductors Science and Technology, ISSN 0953-2048, E-ISSN 1361-6668, Vol. 32, no 3, article id 035008Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the impact of using III-nitride semiconductors (GaN, AlN) as substrates for ultrathin (11 nm) superconducting films of NbTiN deposited by reactive magnetron sputtering. The resulting NbTiN layers are (111)-oriented, fully relaxed, and they keep an epitaxial relation with the substrate. The higher critical superconducting temperature (T-c = 11.8 K) was obtained on AIN-on-sapphire, which was the substrate with smaller lattice mismatch with NbTiN. We attribute this improvement to a reduction of the NbTiN roughness, which appears associated with the relaxation of the lattice misfit with the substrate. On AlN-on-sapphire, superconducting nanowire single photon detectors were fabricated and tested, obtaining external quantum efficiencies that are in excellent agreement with theoretical calculations.

  • 27. Machhadani, Houssaine
    et al.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Bougerol, Catherine
    Lequien, Stéphane
    Thomassin, Jean-Luc
    Mollard, Nicolas
    Mukhtarova, Anna
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gérard, Jean-Michel
    Monroy, Eva
    Improvement of the critical temeprature of NbTiN films on III-nitride substrates2019In: Superconductors Science and Technology, ISSN 0953-2048, E-ISSN 1361-6668, Vol. 32, no 035008Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the impact of using III-nitride semiconductors (GaN, AlN) as substrates for ultrathin (11 nm) superconducting films of NbTiN deposited by reactive magnetron sputtering. The resulting NbTiN layers are (111)-oriented, fully relaxed, and they keep an epitaxial relation with the substrate. The higher critical superconducting temperature (T c = 11.8 K) was obtained on AlN-on-sapphire, which was the substrate with smaller lattice mismatch with NbTiN. We attribute this improvement to a reduction of the NbTiN roughness, which appears associated with the relaxation of the lattice misfit with the substrate. On AlN-on-sapphire, superconducting nanowire single photon detectors were fabricated and tested, obtaining external quantum efficiencies that are in excellent agreement with theoretical calculations.

  • 28.
    Mukhtarova, Anna
    et al.
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Redaelli, Luca
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Hazra, Dibyendu
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Machhadani, Houssaine
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Lequien, Stephane
    Univ Grenoble Alpes, CEA, INAC, MEM, 17 Av Martyrs, F-38000 Grenoble, France..
    Hofheinz, Max
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Thomassin, Jean-Luc
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Gustavo, Frederic
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France.;Delft Univ Technol, Kavli Inst Nanosci, Lorentzweig 1, NL-2628 CJ Delft, Netherlands..
    Monroy, Eva
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Gerard, Jean-Michel
    Univ Grenoble Alpes, CEA, INAC, PHELIQS, 17 Av Martyrs, F-38000 Grenoble, France..
    Polarization-insensitive fiber-coupled superconducting-nanowire single photon detector using a high-index dielectric capping layer2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 13, p. 17697-17704Article in journal (Refereed)
    Abstract [en]

    Superconducting-nanowire single photon detectors (SNSPDs) are able to reach near-unity detection efficiency in the infrared spectral range. However, due to the intrinsic asymmetry of nanowires, SNSPDs are usually very sensitive to the polarization of the incident radiation, their responsivity being maximum for light polarized parallel to the nanowire length (transverse-electric (TE) polarization). Here, we report on the reduction of the polarization sensitivity obtained by capping NbN-based SNSPDs with a high-index SiNx dielectric layer, which reduces the permittivity mismatch between the NbN wire and the surrounding area. Experimentally, a polarization sensitivity below 0.1 is obtained both at 1.31 and 1.55 mu m, in excellent agreement with simulations.

  • 29. Mukhtarova, Anna
    et al.
    Redaelli, Luca
    Hazra, Dibyendu
    Machhadani, Houssaine
    Lequien, Stéphane
    Hofheinz, Max
    Thomassin, Jean-Luc
    Gustavo, Frederic
    Zichi, Julien
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Monroy, Eva
    Gérard, Jean-Michel
    Polarization-insensitive fiber-coupled superconducting-nanowire single photon detector using high-index dielectric capping layer2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 13Article in journal (Refereed)
    Abstract [en]

    Superconducting-nanowire single photon detectors (SNSPDs) are able to reach near-unity detection efficiency in the infrared spectral range. However, due to the intrinsic asymmetry of nanowires, SNSPDs are usually very sensitive to the polarization of the incident radiation, their responsivity being maximum for light polarized parallel to the nanowire length (transverse-electric (TE) polarization). Here, we report on the reduction of the polarization sensitivity obtained by capping NbN-based SNSPDs with a high-index SiNx dielectric layer, which reduces the permittivity mismatch between the NbN wire and the surrounding area. Experimentally, a polarization sensitivity below 0.1 is obtained both at 1.31 and 1.55 μm, in excellent agreement with simulations.

  • 30. Neumayer, Sabine M.
    et al.
    Ievlev, Anton V.
    Collins, Liam
    Vasudevan, Rama
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Ovchinnikova, Olga
    Jesse, Stephen
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Rodriguez, Brian J.
    Kalinin, Sergei V.
    Surface Chemistry Controls Anomalous Ferroelectric Behavior in Lithium Niobate2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 34, p. 29153-29160Article in journal (Refereed)
    Abstract [en]

    Polarization switching in ferroelectric materials underpins a multitude of applications ranging from nonvolatile memories to data storage to ferroelectric lithography. While traditionally considered to be a functionality of the material only, basic theoretical considerations suggest that switching is expected to be intrinsically linked to changes in the electrochemical state of the surface. Hence, the properties and dynamics of the screening charges can affect or control the switching dynamics. Despite being recognized for over 50 years, analysis of these phenomena remained largely speculative. Here, we explore polarization switching on the prototypical LiNbO3 surface using the combination of contact mode Kelvin probe force microscopy and chemical imaging by time-of-flight mass-spectrometry and demonstrate pronounced chemical differences between the domains. These studies provide a consistent explanation to the anomalous polarization and surface charge behavior observed in LiNbO3 and point to new opportunities in chemical control of polarization dynamics in thin films and crystals via control of surface chemistry, complementing traditional routes via bulk doping, and substrate-induced strain and tilt systems.

  • 31.
    Ojemyr, Linda Nasvik
    et al.
    Stockholm Univ, Dept Biochem & Biophys, Arrhenius Labs Nat Sci, S-10691 Stockholm, Sweden..
    Sanden, Tor
    Royal Inst Technol, Dept Appl Phys, Stockholm, Sweden..
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Brzezinski, Peter
    Stockholm Univ, Dept Biochem & Biophys, Arrhenius Labs Nat Sci, S-10691 Stockholm, Sweden..
    Membrane-facilitated proton transfer to the surface of a membrane-spanning proton transporter2010In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1797, p. 98-98Article in journal (Other academic)
  • 32.
    Ojemyr, Linda
    et al.
    Stockholm Univ, Arrhenius Labs Nat Sci, Dept Biochem & Biophys, Stockholm, Sweden..
    Sanden, Tor
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Brzezinski, Peter
    Stockholm Univ, Arrhenius Labs Nat Sci, Dept Biochem & Biophys, Stockholm, Sweden..
    Proton transfer along surfaces of membranes and membrane-proteins2008In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1777, p. S94-S94Article in journal (Other academic)
  • 33.
    Pathak, Anuj
    et al.
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden..
    Bergstrand, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Sender, Vicky
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden..
    Spelmink, Laura
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden..
    Aschtgen, Marie-Stephanie
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden..
    Muschiol, Sandra
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden..
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Henriques-Normark, Birgitta
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, SE-17177 Stockholm, Sweden.;Nanyang Technol Univ, Lee Kong Chian Sch Med LKC, Singapore 639798, Singapore.;Nanyang Technol Univ, Singapore Ctr Environm Life Sci Engn SCELSE, Singapore 639798, Singapore.;Karolinska Univ Hosp, Dept Clin Microbiol, SE-17176 Stockholm, Sweden..
    Factor H binding proteins protect division septa on encapsulated Streptococcus pneumoniae against complement C3b deposition and amplification2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3398Article in journal (Refereed)
    Abstract [en]

    Streptococcus pneumoniae evades C3-mediated opsonization and effector functions by expressing an immuno-protective polysaccharide capsule and Factor H (FH)-binding proteins. Here we use super-resolution microscopy, mutants and functional analysis to show how these two defense mechanisms are functionally and spatially coordinated on the bacterial cell surface. We show that the pneumococcal capsule is less abundant at the cell wall septum, providing C3/C3b entry to underlying nucleophilic targets. Evasion of C3b deposition at division septa and lateral amplification underneath the capsule requires localization of the FH-binding protein PspC at division sites. Most pneumococcal strains have one PspC protein, but successful lineages in colonization and disease may have two, PspC1 and PspC2, that we show affect virulence differently. We find that spatial localization of these FH-recruiting proteins relative to division septa and capsular layer is instrumental for pneumococci to resist complement-mediated opsonophagocytosis, formation of membrane-attack complexes, and for the function as adhesins.

  • 34. Peng, Xingyun
    et al.
    Huang, Bingru
    Pu, Rui
    Liu, Haichun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Zhang, Tao
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zhan, Qiuqiang
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Fast upconversion super-resolution microscopy with 10 μs per pixel dwell times2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 4, p. 1563-1569Article in journal (Refereed)
  • 35.
    Reindl, Marcus
    et al.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Huber, Daniel
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Schimpf, Christian
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon F. Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Rota, Michele B.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Huang, Huiying
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Johannes Kepler Univ Linz, Linz Inst Technol, A-4040 Linz, Austria..
    Trotta, Rinaldo
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    All-photonic quantum teleportation using on-demand solid-state quantum emitters2018In: Science Advances, E-ISSN 2375-2548, Vol. 4, no 12, article id eaau1255Article in journal (Refereed)
    Abstract [en]

    All-optical quantum teleportation lies at the heart of quantum communication science and technology. This quantum phenomenon is built up around the nonlocal properties of entangled states of light that, in the perspective of real-life applications, should be encoded on photon pairs generated on demand. Despite recent advances, however, the exploitation of deterministic quantum light sources in push-button quantum teleportation schemes remains a major open challenge. Here, we perform an important step toward this goal and show that photon pairs generated on demand by a GaAs quantum dot can be used to implement a teleportation protocol whose fidelity violates the classical limit (by more than 5 SDs) for arbitrary input states. Moreover, we develop a theoretical framework that matches the experimental observations and that defines the degree of entanglement and indistinguishability needed to overcome the classical limit independently of the input state. Our results emphasize that on-demand solid-state quantum emitters are one of the most promising candidates to realize deterministic quantum teleportation in practical quantum networks.

  • 36.
    Sachl, Radek
    et al.
    ASCR, J Heyrovsky Inst Phys Chem, Vvi, Dept Biophys Chem, Prague, Czech Republic..
    Bergstrand, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH Royal Inst Technol, Dept Appl Phys, Expt Biomol Phys, S-10691 Stockholm, Sweden..
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. KTH Royal Inst Technol, Dept Appl Phys, Expt Biomol Phys, S-10691 Stockholm, Sweden..
    Hof, Martin
    ASCR, J Heyrovsky Inst Phys Chem, Vvi, Dept Biophys Chem, Prague, Czech Republic..
    Erratum to: Fluorescence correlation spectroscopy diffusion laws in the presence of moving nanodomains2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 18, article id 189601Article in journal (Refereed)
  • 37.
    Schaper, Klaus
    et al.
    Univ Dusseldorf, Dept Chem, D-40225 Dusseldorf, Germany..
    Bier, Brigitte
    Univ Dusseldorf, Dept Chem, D-40225 Dusseldorf, Germany..
    Taureg, Patrick
    Univ Dusseldorf, Dept Chem, D-40225 Dusseldorf, Germany..
    von Dahlen, Steffen
    Pfiffi, Daniela
    Seidel, Claus A. M.
    Chmyrov, Andriy
    KTH.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    PHYS 624-Strategies to improve signal strength and photostability of fluorophors in single molecule spectroscopy2007In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 234Article in journal (Other academic)
  • 38.
    Schollhammer, Jean
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Birefringence-free lithium niobate waveguides2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
  • 39.
    Schollhammer, Jean
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Modal birefringence-free lithium niobate waveguides2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 18, p. 3578-3581Article in journal (Refereed)
    Abstract [en]

    We investigate polarization-insensitive waveguide designs afforded by the interplay of material and waveguide birefringence in LiNbO3-on-insulator photonic wires. Fundamental mode birefringence-free operation in the 0.8-1.8 mu m spectral range is predicted for a suitable choice of waveguide widths in the 375-600 nm range. Optimized buried waveguide designs yield broadband (1350-1625 nm) index matching between TE00 and TM00 modes. Furthermore, simultaneous phase- and group-velocity matching at infrared wavelengths appears feasible for pulse durations as short as 100 fs.

  • 40.
    Schweickert, Lucas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Fognini, A.
    Zadeh, I. E.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Generating, manipulating and detecting quantum states of light at the nanoscale2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    We generate, manipulate and detect light at the single photon level with semiconducting and superconducting nanowires.

  • 41.
    Schweickert, Lucas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    da Silva, Saimon Filipe Covre
    Huang, Huiying
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reindl, Marcus
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trotta, Rinaldo
    Rastelli, Armando
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    On-demand generation of background-free single photons from a solid-state source2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 9, article id 093106Article in journal (Refereed)
    Abstract [en]

    True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g((2)) (0) = (7.5 +/- 1.6) x 10(-5) without any background subtraction or data processing. To this date, this is the lowest value of g((2)) (0) Peported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056 +/- 0.0007) s(-1) and (0.017 +/- 0.001) s(-1), respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.

  • 42.
    Schöll, Eva
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hanschke, Lukas
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reindl, Marcus
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon Filipe Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trotta, Rinaldo
    Sapienza Univ Roma, Dipartimento Fis, Piazzale A Moro 1, I-00185 Rome, Italy..
    Finley, Jonathan J.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Mueller, Kai
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Resonance Fluorescence of GaAs Quantum Dots with Near-Unity Photon Indistinguishability2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, no 4, p. 2404-2410Article in journal (Refereed)
    Abstract [en]

    Photonic quantum technologies call for scalable quantum light sources that can be integrated, while providing the end user with single and entangled photons on demand. One promising candidate is strain free GaAs/A1GaAs quantum dots obtained by aluminum droplet etching. Such quantum dots exhibit ultra low multi-photon probability and an unprecedented degree of photon pair entanglement. However, different to commonly studied InGaAs/GaAs quantum dots obtained by the Stranski-Krastanow mode, photons with a near-unity indistinguishability from these quantum emitters have proven to be elusive so far. Here, we show on-demand generation of near-unity indistinguishable photons from these quantum emitters by exploring pulsed resonance fluorescence. Given the short intrinsic lifetime of excitons and trions confined in the GaAs quantum dots, we show single photon indistinguishability with a raw visibility of V-raw = (95.0(-6.1)(+5.0))%, without the need for Purcell enhancement. Our results represent a milestone in the advance of GaAs quantum dots by demonstrating the final missing property standing in the way of using these emitters as a key component in quantum communication applications, e.g., as quantum light sources for quantum repeater architectures.

  • 43.
    Stensson, Katarina
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Björk, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Measurement of the two-time intensity-correlation function of arbitrary statesManuscript (preprint) (Other academic)
    Abstract [en]

    For light intensity correlations measurements, different methods are used in the high photon number or high intensity regime and in the single- and two-photon regime. Hence, there is an unfortunate measurement ``gap’’ primarily for multi-photon, quantum states. These states, for example multi-photon Fock states will be increasingly important in the realization of quantum technologies and in exploring the boundaries between quantum and classical optics. We show that a na\"{i}ve approach, based on attenuation, state splitting, and two-detector correlation, can give the correct two-time intensity correlation for any state. We analyze how added losses decrease the measurement’s systematic error. The price to be paid is that the losses increase the measurement statistical error or alternatively, increases the acquisition time for a given tolerable level of statistical error. We have experimentally demonstrated the feasibility of the method for a coherent state and a quasi-thermal state. The method is easy to implement in any laboratory and will simplify characterization of medium and highly excited non-classical states as they become experimentally available.

  • 44.
    Tornmalm, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Fluorescence-based Transient State Monitoring for biomolecular, cellular and label-free studies2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fluorophore blinking dynamics are highly sensitive to the local environment and can be used as an additional readout parameter to increase the information gained from existing fluorescence techniques.The origin of these blinking patterns are photophysical transitions to and from a manifold of non-luminescent states. The long lifetime of these dark transient states, typically 103 to 106 times longer than the fluorescent state, gives them correspondingly more time to sense their environment. For this reason, fluorophore blinking dynamics are particularly sensitive to low frequency events, such as diffusion-mediated interactions between the fluorophore and dilute species.

    Transient State (TRAST) monitoring has been developed to quantify fluorophore blinking dynamics in a simple and widely applicable manner. TRAST does not need to resolve individual blinking events, but instead monitors the average fluorescence intensity in response to a modulated excitation. By systematically varying the modulation parameters, the transient state kinetics of the sample are mapped out. Without the need for time-resolved detection, a regular camera can be used to image blinking dynamics with high spatial resolution.

    This thesis presents TRAST characterizations of common autofluorescent compounds and demonstrates their ability to sense relevant biological parameters such as oxygen concentration and redox potential. In Papers I and II, the autofluorescent co-enzymes flavin and NAD(P)H were studied, and label-free imaging of local redox variations within cells was demonstrated. Perturbing the cells, through dilute additions of mitochondrial uncouplers, revealed a strong andlocalized response in the TRAST images. In Paper III we studied tryptophan autofluorescence and used it to detect conformational changes in an unlabeled spider silk protein.

    Labeling with external fluorophores can add further specificity to the TRAST measurements. In Paper IV, TRAST was used to monitor diffusion-mediated interactions between lipids and receptors in a cell membrane, including the influence of receptor activation. In Paper V we tracked folding of RNA into G-quadruplexes in live cells, monitored via the isomerization properties of an attached cyanine dye.

  • 45.
    Tornmalm, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Kitamura, Akira
    Hokkaido University, Sapporo.
    Kinjo, Masataka
    Hokkaido University, Sapporo.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trans-cis isomerization kinetics of cyanine dyes reports on the folding states of RNA G-quadruplexes in live cellsManuscript (preprint) (Other academic)
    Abstract [en]

    Guanine (G)-rich sequences in nucleic acids are prone to assemble into four-stranded structures, called G-quadruplexes. Abnormal GGGGCC repeat elongations have been associated with Amyotrophic lateral sclerosis and fronto-temporal dementia. In particular, the folding states of such elongations are believed to play a central role in the development of these diseases. Since most studies of G-quadruplex structures are made in vitro, it is highly relevant to clarify what the structures of elongated GGGGCC repeats look like in vivo. However, due to methodological constraints, evidence of specific structures of such GGGGCC repeats in vivo is sparse.

    In this work, we devised a readout strategy, exploiting the sensitivity of trans-cis isomerization of cyanine dyes to local viscosity and sterical constraints. We show that the folding states of cyanine-labeled RNA molecules, and in particular of G-quadruplexes, can be identified in a sensitive manner by this strategy. The isomerization kinetics, monitored via the fluorescence blinking generated upon transitions between a fluorescent trans isomer and a non-fluorescent cis isomer, was first characterized for RNA molecules with GGGGCC repeats in aqueous solution using Fluorescence correlation spectroscopy (FCS) and transient state (TRAST) monitoring. With TRAST, monitoring the isomerization kinetics from how the average fluorescence intensity varies with modulation characteristics of a laser excitation source, we could then also detect the folding states of RNA molecules in living cells. This approach is robust, applicable on a broad range of biological samples and can also be extended to study folding or misfolding of proteins and biomolecules in general.

  • 46.
    Tornmalm, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Piguet, Joachim
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Chmyrov, Volodymyr
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Transient state imaging of intermittent interactions between lipids and receptor proteins in artificial and live cell membranesManuscript (preprint) (Other academic)
    Abstract [en]

    Transient collisional interactions between lipids and membrane proteins play an important role in modulating cellular functions but occur at frequencies too low to be readily observable via fluorescence imaging or quenching studies. We used transient state imaging (TRAST) to quantify those interaction in living cells. This method combines sensitive detection of fluorescence from fluorophore marker molecules with the ability to monitor their long-lived dark triplet states, highly sensitive to molecular interactions in artificial and live cell membranes.

    By TRAST we first determined the dark transient state kinetics of 7-nitrobenz-2-oxa-1,3-diazole-4-yl (NBD), an extensively used biomembrane fluorophore, available as a label on a wide range of lipids and sterols. We then measured quenching of NBD triplet states by spin-labels, in the membranes of small unilamellar vesicles (SUVs), and studied how it depends on the fluorescent lipid-derivative type and on the position of the spin label in the membranes. By the same strategy, we then quantified the collisional quenching of NBD-lipid derivatives and spin-labelled stearic acids in live cell plasma membranes.

    Finally, we extended the method to study the collisional interactions between G-Protein Coupled Receptors (GPCRs), covalently labelled with the spin label TEMPO, and NBD-lipid derivatives, in the plasma membranes of living cells. Thereby, we could resolve transient interactions between the GPCRs and lipids with different hydrophilic heads or sterols, and how these interactions were changed upon activation of the GPCR by an agonist. The presented approach offers a straightforward and widely applicable means to characterize and image transient interactions in live cell membranes, of large biomedical relevance.

  • 47.
    Tornmalm, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Sandberg, Elin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rabasovic, Mihailo
    Institute of Physics, University of Belgrade.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Local redox conditions in cells imaged via non-fluorescent transient states of NAD(P)HManuscript (preprint) (Other academic)
    Abstract [en]

    The autofluorescent coenzyme nicotinamide adenine dinucleotide (NADH) and its phosphorylated form (NADPH) are major determinants of cellular redox balance. Both their fluorescence intensities and lifetimes are extensively used as label-free readouts in cellular metabolic imaging studies. Here, we introduce fluorescence blinking of NAD(P)H as an additional, orthogonal readout in such studies. Blinking of fluorophores and their underlying dark state transitions are specifically sensitive to redox conditions and oxygenation, parameters of particular relevance in cellular metabolic studies. We show that such dark state transitions in NAD(P)H can be quantified via the average fluorescence intensity recorded upon modulated one-photon excitation, so-called transient state (TRAST) monitoring. Thereby, transitions in NAD(P)H, previously only accessible from elaborate spectroscopic cuvette measurements, can be imaged at subcellular resolution in live cells. We then demonstrate that these transitions can be imaged with a standard laser-scanning confocal microscope and two-photon excitation, in parallel with regular fluorescence lifetime imaging (FLIM). In contrast to FLIM, TRAST imaging of NAD(P)H clearly reveals an altered oxidative environment in the cytosols of cells treated with a mitochondrial un-coupler. We propose TRAST imaging as a straightforward and widely applicable modality, extending the range of information obtainable from cellular metabolic imaging of NAD(P)H fluorescence.

  • 48.
    Tornmalm, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Label-free monitoring of ambient oxygenation and redox conditions using the photodynamics of flavin compounds and transient state (TRAST) spectroscopy2018In: Methods, ISSN 1046-2023, E-ISSN 1095-9130, Vol. 140, p. 178-187Article in journal (Refereed)
    Abstract [en]

    Transient state (TRAST) monitoring can determine population dynamics of long-lived, dark transient states of fluorescent molecules, detecting only the average fluorescence intensity from a sample, when subject to different excitation pulse trains. Like Fluorescence Correlation Spectroscopy (FCS), TRAST unites the detection sensitivity of fluorescence with the environmental sensitivity of long-lived non-fluorescent states, but does not rely on detection of stochastic fluorescence fluctuations from individual molecules. Relaxed requirements on noise suppression, detection quantum yield and time-resolution of the instrument, as well as on fluorescence brightness of the molecules studied, make TRAST broadly applicable, opening also for investigations based on less bright, auto-fluorescent molecules. In this work, we applied TRAST to study the transient state population dynamics within the auto-fluorescent coenzymes flavin adenine dinucleotide (FAD) and flavin-mononucleotide (FMN). From the experimental TRAST data, we defined state models, and determined rate parameters for triplet state and redox transitions within FMN and FAD, stacking and un-stacking rates of external redox active quenching agents and by the adenine moiety of FAD itself. TRAST experiments were found to be well capable to resolve these transitions in FMN and FAD, and to track how the transitions are influenced by ambient oxygenation and redox conditions. This work demonstrates that TRAST provides a useful tool to follow local oxygenation and redox conditions via FMN and FAD fluorescence, and forms the basis for measurements on flavoproteins and of redox and metabolic conditions in more complex environments, such as in live cells.

  • 49.
    Wengerowsky, Soeren
    et al.
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria..
    Joshi, Siddarth Koduru
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria.;HH Wills Phys Lab, Quantum Engn Technol Labs, Bristol BS8 1FD, Avon, England.;Univ Bristol, Dept Elect & Elect Engn, Bristol BS8 1UB, Avon, England..
    Steinlechner, Fabian
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria.;Fraunhofer Inst Appl Opt & Precis Engn IOF Jena, D-07745 Jena, Germany.;Friedrich Schiller Univ Jena, Abbe Ctr Photon, D-07745 Jena, Germany..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Single Quantum BV, NL-2628 CJ Delft, Netherlands..
    Dobrovolskiy, Sergiy M.
    Single Quantum BV, NL-2628 CJ Delft, Netherlands..
    van der Molen, Rene
    Single Quantum BV, NL-2628 CJ Delft, Netherlands..
    Los, Johannes W. N.
    Single Quantum BV, NL-2628 CJ Delft, Netherlands..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Single Quantum BV, NL-2628 CJ Delft, Netherlands..
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Mura, Alberto
    Ist Nazl Ric Metrol, I-10135 Turin, Italy..
    Calonico, Davide
    Ist Nazl Ric Metrol, I-10135 Turin, Italy..
    Inguscio, Massimo
    European Lab Nonlinear Spect LENS, I-50019 Sesto Fiorentino, Italy.;Univ Florence, Dept Phys & Astron, I-50019 Sesto Fiorentino, Italy.;CNR, I-00185 Rome, Italy..
    Huebel, Hannes
    Austrian Inst Technol, Ctr Digital Safety & Secur, A-1210 Vienna, Austria..
    Bo, Liu
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria.;Natl Univ Def Technol, Coll Adv Interdisciplinary Studies, Changsha 410073, Hunan, Peoples R China..
    Scheidl, Thomas
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Univ Vienna, Quantum Opt Quantum Nanophys & Quantum Informat, A-1090 Vienna, Austria..
    Zeilinger, Anton
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Univ Vienna, Quantum Opt Quantum Nanophys & Quantum Informat, A-1090 Vienna, Austria..
    Xuereb, Andre
    Univ Malta, Dept Phys, MSD-2080 Msida, Malta..
    Ursin, Rupert
    Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria..
    Entanglement distribution over a 96-km-long submarine optical fiber2019In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 14, p. 6684-6688Article in journal (Refereed)
    Abstract [en]

    Quantum entanglement is one of the most extraordinary effects in quantum physics, with many applications in the emerging field of quantum information science. In particular, it provides the foundation for quantum key distribution (QKD), which promises a conceptual leap in information security. Entanglement-based QKD holds great promise for future applications owing to the possibility of device-independent security and the potential of establishing global-scale quantum repeater networks. While other approaches to QKD have already reached the level of maturity required for operation in absence of typical laboratory infrastructure, comparable field demonstrations of entanglement-based QKD have not been performed so far. Here, we report on the successful distribution of polarization-entangled photon pairs between Malta and Sicily over 96 km of submarine optical telecommunications fiber. We observe around 257 photon pairs per second, with a polarization visibility above 90%. Our results show that QKD based on polarization entanglement is now indeed viable in long-distance fiber links. This field demonstration marks the longest-distance distribution of entanglement in a deployed telecommunications network and demonstrates an international submarine quantum communication channel. This opens up myriad possibilities for future experiments and technological applications using existing infrastructure.

  • 50.
    Xu, Lei
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Braun, Laura J.
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, Stockholm, Sweden..
    Rönnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Aspenstrom, Pontus
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, Stockholm, Sweden..
    Gad, Annica K. B.
    Univ Madeira, CQM, Campus Penteada, P-9020105 Funchal, Portugal..
    Nanoscale localization of proteins within focal adhesions indicates discrete functional assemblies with selective force-dependence2018In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 285, no 9, p. 1635-1652Article in journal (Refereed)
    Abstract [en]

    Focal adhesions (FAs) are subcellular regions at the micrometer scale that link the cell to the surrounding microenvironment and control vital cell functions. However, the spatial architecture of FAs remains unclear at the nanometer scale. We used two-color and three-color super-resolution stimulated emission depletion microscopy to determine the spatial distributions and co-localization of endogenous FA components in fibroblasts. Our data indicate that adhesion proteins inside, but not outside, FAs are organized into nanometer size units of multi-protein assemblies. The loss of contractile force reduced the nanoscale co-localization between different types of proteins, while it increased this co-localization between markers of the same type. This suggests that actomyosin-dependent force exerts a nonrandom, specific, control of the localization of adhesion proteins within cell-matrix adhesions. These observations are consistent with the possibility that proteins in cell-matrix adhesions are assembled in nanoscale particles, and that force regulates the localization of the proteins therein in a protein-specific manner. This detailed knowledge of how the organization of FA components at the nanometer scale is linked to the capacity of the cells to generate contractile forces expands our understanding of cell adhesion in health and disease.

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