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  • 1. Akram, M. N.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Berggren, J.
    Experimental evaluation of carrier transport, gain, T0 and chirp of 1.55 mm MQW structures with different barrier compositions2005In: 31st European Conference on Optical Communications (ECOC 2005), 2005, Institution of Engineering and Technology, 2005, Vol. 2005, no CP502, p. 297-298Conference paper (Refereed)
    Abstract [en]

    Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW test structures. Shallow InGaAlAs barrier QW showed faster carrier transport. Semi-insulating regrown FP lasers with InGaAlAs barrier QW showed improved high temperature operation, modal gain, differential modal gain and chirp.

  • 2. Al-Awis, S. N.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, O.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Fattah, A. Y.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Phenomenological formula for modelling of physical layer impairments in elastic optical networks2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    An empirical modelling technique is introduced to estimate impact of physical layer impairments in elastic optical networks, which can be used to evaluate transmission quality. The model has been verified experimentally with accuracy beyond (97.3%). © 2015 OSA.

  • 3. Bai, Songang
    et al.
    Li, Qiang
    Zhang, Han
    Chen, Xingxing
    Luo, Si
    Gong, Hanmo
    Yang, Yuanqing
    Zhao, Ding
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Large third-order nonlinear refractive index coefficient based on gold nanoparticle aggregate films2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 14, article id 141111Article in journal (Refereed)
    Abstract [en]

    Au nanoparticles show large third-order nonlinear effect and ultra-fast response. Here a high nonlinear aggregate film based on self-assembled gold nanoparticles is reported and its third-order nonlinear refractive index coefficient is measured by Z-scan experiment. The third-order nonlinear refractive index coefficient of the Au nanoparticle aggregate film (gamma(1) = 9.2 x 10(-9) cm(2)/W) is found to be larger than that of an 8-nm-thick sputtered Au film (gamma(2)= 6.5 x 10(-9) cm(2)/W). This large nonlinear effect can be attributed to the strong field enhancement due to localized plasmon resonances between Au nanoparticles. The result shows that the self-assembled Au nanoparticle aggregate film could be a promising candidate as a third-order nonlinear optical material.

  • 4. Chacinski, M.
    et al.
    Chitica, N.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Transmission of 40 Gb/s over 55 m multimode fiber using 12 GHz bandwidth system based on vertical-cavity surface-emitting laser2014In: Asia Communications and Photonics Conference, ACP, 2014Conference paper (Refereed)
    Abstract [en]

    Error free transmission (E-12) over 55 m long standard MMF at 40 Gb/s data rate is demonstrated with moderate signal conditioning on the VCSEL. The VCSEL has a-3 dBe bandwidth of 15 GHz resulting in system bandwidth of 12GHz, giving 3.3 bit/s/Hz coding efficiency.

  • 5. Chang, Lantian
    et al.
    Weiss, Nicolas
    van Leeuwen, Ton G.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    de Ridder, Rene M.
    Worhoff, Kerstin
    Subramaniam, Vinod
    Kanger, Johannes S.
    Chip based common-path optical coherence tomography system with an on-chip microlens and multi-reference suppression algorithm2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 12, p. 12635-12650Article in journal (Refereed)
    Abstract [en]

    We demonstrate an integrated optical probe including an on-chip microlens for a common-path swept-source optical coherence tomography system. This common-path design uses the end facet of the silicon oxynitride waveguide as the reference plane, thus eliminating the need of a space-consuming and dispersive on-chip loop reference arm, thereby obviating the need for dispersion compensation. The on-chip micro-ball lens eliminates the need of external optical elements for coupling the light between the chip and the sample. The use of this lens leads to a signal enhancement up to 37 dB compared to the chip without a lens. The light source, the common-path arm and the detector are connected by a symmetric Y junction having a wavelength independent splitting ratio (50/50) over a much larger bandwidth than can be obtained with a directional coupler. The signal-to-noise ratio of the system was measured to be 71 dB with 2.6 mW of power on a mirror sample at a distance of 0.3 mm from the waveguide end facet. Cross-sectional OCT images of a layered optical phantom sample are demonstrated with our system. A method, based on an extended Fourier-domain OCT model, for suppressing ghost images caused by additional parasitic reference planes is experimentally demonstrated.

  • 6.
    Chen, Xi
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Photothermal Effect in Plasmonic Nanostructures and its Applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

      Plasmonic resonances are characterized by enhanced optical near field and subwavelength power confinement. Light is not only scattered but also simultaneously absorbed in the metal nanostructures. With proper structural design, plasmonic-enhanced light absorption can generate nanoscopically confined heat power in metallic nanostructures, which can even be temporally modulated by varying the pump light. These intrinsic characters of plasmonic nanostructures are investigated in depth in this thesis for a range of materials and nanophotonic applications.

      The theoretical basis for the photothermal phenomenon, including light absorption, heat generation, and heat conduction, is coherently summarized and implemented numerically based on finite-element method. Our analysis favours disk-pair and particle/dielectric-spacer/metal-film nanostructures for their high optical absorbance, originated from their antiparallel dipole resonances.

      Experiments were done towards two specific application directions. First, the manipulation of the morphology and crystallinity of Au nanoparticles (NPs) in plasmonic absorbers by photothermal effect is demonstrated. In particular, with a nanosecond-pulsed light, brick-shaped Au NPs are reshaped to spherical NPs with a smooth surface; while with a 10-second continuous wave laser, similar brick-shaped NPs can be annealed to faceted nanocrystals. A comparison of the two cases reveals that pumping intensity and exposure time both play key roles in determining the morphology and crystallinity of the annealed NPs.

      Second, the attempt is made to utilize the high absorbance and localized heat generation of the metal-insulator-metal (MIM) absorber in Si thermo-optic switches for achieving all-optical switching/routing with a small switching power and a fast transient response. For this purpose, a numerical study of a Mach-Zehnder interferometer integrated with MIM nanostrips is performed. Experimentally, a Si disk resonator and a ring-resonator-based add-drop filter, both integrated with MIM film absorbers, are fabricated and characterized. They show that good thermal conductance between the absorber and the Si light-guiding region is vital for a better switching performance.

      Theoretical and experimental methodologies presented in the thesis show the physics principle and functionality of the photothermal effect in Au nanostructures, as well as its application in improving the morphology and crystallinity of Au NPs and miniaturized all-optical Si photonic switching devices.

  • 7.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zhao, Ding
    Li, Qiang
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ordered Au nanocrystals on a substrate formed by light-induced rapid annealing2014In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 3, p. 1756-1762Article in journal (Refereed)
    Abstract [en]

    Light-induced rapid annealing (LIRA) is a widely used method to modify the morphology and crystallinity of noble metal nanoparticles, and the nanoparticles generally evolve into nanospheres. It is rather challenging to form faceted Au nanocrystals on a substrate using LIRA. Here the formation of spatially ordered Au nanocrystals using a continuous wave infrared laser is reported, assisted by a metamaterial perfect absorber. Faceted Au nanocrystals in truncated-octahedral or multi-twinned geometries can be obtained. The evolution of morphology and crystallinity of the Au nanoparticles during laser annealing is also revealed, where the crystal grain growth and the surface melting are shown to play key roles in nanocrystal formation. The evolution of morphology also gives the freedom of tuning the absorption spectrum of the metamaterial absorber. These findings provide a novel way for tailoring the morphology and crystallinity of metallic nanoparticles and may pave the way to fabricate refined nano-devices in many potential applications for optics, electronics, catalysis, surface-chemistry and biology.

  • 8.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Shi, Yuechun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Photothermal switching of SOI-waveguide-based Mach-Zehnder interferometer with integrated plasmonic nanoheater2014In: Plasmonics, ISSN 1557-1963, Vol. 9, no 5, p. 1197-1205Article in journal (Refereed)
    Abstract [en]

    We theoretically and numerically investigate photothermal switching of a Mach-Zehnder interferometer (MZI) based on two Si waveguides integrated with plasmonic nanoheater. The nanoheater is a composite nanowire with Au/Al2O3/Au three-layer structure, which is designed to have a high-efficient optical absorption peak at wavelength of 1064 nm. Based on this finding, we further analyze a MZI built with two 40 μm-long symmetric waveguide branches, each integrated with a 20 μm-long nanoheater. The optical switching power of the MZI device is 190 mW (280 mW) for the capped (buried) channel waveguide, when pumped by a circular Gaussian beam with a waist of 10 μm. Alternatively, the switching power can be reduced to 38 mW (56 mW) by using an astigmatic Gaussian beam, with a semi-major axis of 10 μm and an aspect ratio of 5. The switching response time of the MZI is 0.7 μs (1.0 μs) for capped (buried) channel waveguide design. Our design opens a new route for optically driven non-contact optical on-off switching with sub-microsecond time response.

  • 9.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Nanosecond Photothermal Effects in Plasmonic Nanostructures2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 3, p. 2550-2557Article in journal (Refereed)
    Abstract [en]

    Photothermal effects in plasmonic nanostructures have great potentials in applications for photothermal cancer therapy, optical storage, thermo-photovoltaics, etc. However, the transient temperature behavior of a nanoscale material system during an ultrafast photothermal process has rarely been accurately investigated. Here a heat transfer model is constructed to investigate the temporal and spatial variation of temperature in plasmonic gold nanostructures. First, as a benchmark scenario, we study the light-induced heating of a gold nanosphere in water and calculate the relaxation time of the nanosphere excited by a modulated light. Second, we investigate heating and reshaping of gold nanoparticles in a more complex metamaterial absorber structure induced by a nanosecond pulsed light. The model shows that the temperature of the gold nanoparticles can be raised from room temperature to >795 K in just a few nanoseconds with a low light luminance, owing to enhanced light absorption through strong plasmonic resonance. Such quantitative predication of temperature change, which Is otherwise formidable to measure experimentally, can serve as an excellent guideline for designing devices for ultrafast photothermal applications.

  • 10.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Shi, Yuechun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Lou, Fei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Photothermally tunable silicon microring-resonator-based optical add-drop filterManuscript (preprint) (Other academic)
    Abstract [en]

    A themro-optic (TO) silicon photonic add-drop filterwith small switching power and fast response is experimentallydemonstrated. We propose that metal-insulator-metal (MIM)absorbers can be integrated into the silicon TO devices, acting asan efficient and localized heat source. The MIM absorber designintroduces less thermal capacity to the device, comparing to theelectrically driven heater used in conventional TO devices. As a keyelement in silicon photonics, microring resonators have applicationin wavelength-division-multiplexing (WDM) devices, owning to theirunique spectrum properties. In this work, a silicon microring add-dropfilter is equipped with a MIM absorber. Experimentally, the deviceshows a measured optical response time of 5.0 μs and pumping powerderivative of the wavelength shift of 60 pm/mW.

  • 11.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Shi, Yuechun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Nanjing University, China.
    Lou, Fei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Photothermally tunable silicon-microring-based optical add-drop filter through integrated light absorber2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 21, p. 25233-25241Article in journal (Refereed)
    Abstract [en]

    An optically pumped thermo-optic (TO) silicon ring add-drop filter with fast thermal response is experimentally demonstrated. We propose that metal-insulator-metal (MIM) light absorber can be integrated into silicon TO devices, acting as a localized heat source which can be activated remotely by a pump beam. The MIM absorber design introduces less thermal capacity to the device, compared to conventional electrically-driven approaches. Experimentally, the absorber-integrated add-drop filter shows an optical response time of 13.7 mu s following the 10%-90% rule (equivalent to a exponential time constant of 5 mu s) and a wavelength shift over pump power of 60 pm/mW. The photothermally tunable add-drop filter may provide new perspectives for all-optical routing and switching in integrated Si photonic circuits.

  • 12. Chen, Xingxing
    et al.
    Chen, Yu-Hui
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Blaikie, Richard J.
    Ding, Boyang
    Control of fluorescence enhancement and directionality upon excitations in a thin-film system2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 10, p. 2222-2229Article in journal (Refereed)
    Abstract [en]

    Nanostructures with various configurations have been extensively used to engineer the emission properties of embedded fluorophores, but lack the flexibility to dynamically control fluorescence. Here we report a thin-film cavity system, comprising a quarter wavelength thick dye-doped dielectric coating on a reflecting surface, in which the fluorescence enhancement and directionality can be significantly modified by altering the illumination angle. The configuration of the cavity yields absorption properties that are highly dependent on illumination angles, due to the coupling between molecular absorption and Fabry-Perot resonances. Therefore the fluorescence intensity relating to the angle-dependent absorbing efficiency varies with illumination angles. In addition, as a result of synergy between intrinsic absorption of the reflecting surface, Fabry-Perot and surface-plasmon-polariton resonances and illumination-angle dependent excitation efficiencies for differently located molecules, the global emission intensity, including emission from dyes at all locations, can be directionally redistributed by altering the illumination angle.

  • 13. Chen, Xingxing
    et al.
    Gong, Hanmo
    Dai, Shuowei
    Zhao, Ding
    Yang, Yuanqing
    Li, Qiang
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Near-infrared broadband absorber with film-coupled multilayer nanorods2013In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 38, no 13, p. 2247-2249Article in journal (Refereed)
    Abstract [en]

    Turning the surfaces of noble metals (metasurfaces) into black (highly absorptive) surfaces can be potentially applied in thermophotovoltaics, sensing, tailoring thermal emissivity, etc. Here we demonstrate an extremely broadband absorber for the 900-1600 nm wavelength range with robust high absorption efficiency. The inexpensive droplet evaporation method is implemented to create patterns of nanoparticles dispersed on a gold film spaced by a thin dielectric layer. The diversity of the complicated random stacking of the chemically synthesized gold nanorods is the major factor for the broad absorption band. Such a metamaterial absorber may pave the way for cost-effective manufacture of large-area black metasurfaces.

  • 14. Chen, Xingxing
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Blaikie, Richard J.
    Ding, Boyang
    Illumination Dependent Optical Properties of Plasmonic Nanorods Coupled to Thin-Film Cavities2016In: Plasmonics, ISSN 1557-1955, E-ISSN 1557-1963, Vol. 11, no 4, p. 1101-1107Article in journal (Refereed)
    Abstract [en]

    The scattering spectra and intensity of gold nanorods placed at varied distances above gold films have been simulated and measured under various conditions, demonstrating that scattering characteristics of the nanorod-film system are highly dependent on illumination conditions. Studying the surrounding electric fields of nanorods reveals that the illumination-dependent properties of the system are induced by the interference in the nanorod-film system. Both simulations and experiments show that optimising the nanorod-film distance can greatly enhance scattering magnitudes up to similar to 20 times for certain illumination conditions. We propose an application of the studied system in facilitating photo-thermal conversion.

  • 15. Chen, Xingxing
    et al.
    Yang, Yuanqing
    Chen, Yu-Hui
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Blaikie, Richard J.
    Ding, Boyang
    Probing Plasmonic Gap Resonances between Gold Nanorods and a Metallic Surface2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 32, p. 18627-18634Article in journal (Refereed)
    Abstract [en]

    The plasmonic resonances in individual gold nanorods nanoscopically coupled to a gold film with different gap spacing have been experimentally and theoretically investigated. The spectral widths, wavelengths, and optical polarizabilities of the maxima in measured single-nanopartide scattering spectra are significantly modified as the gap distance changes in the sub-20 nm domain. Comparing the experimental data with numerical simulations reveals that these modifications arise from the complex hybridization of several dipolar and multipolar plasmon modes that are strongly localized at the gap. These plasmon gap modes have distinct resonant and spatial characteristics as a result of near-field interaction between the elongated nanorods and the gold film. Additionally, the excitation of these gap modes is highly dependent on the gap spacing. Finally, we also discuss influences of these plasmonic modes on absorption properties of the system and propose a potential application of the studied structures in facilitating photothermal conversion.

  • 16.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Fabrication and Characterization of Plasmonic Nanophotonic Absorbers and Waveguides2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plasmonics is a promising field of nanophotonics dealing with light interaction with metallic nanostructures. In such material systems, hybridizationof photons and collective free-electron oscillation can result in sub-wavelength light confinement. The strong light-matter interaction can be harnessed for,among many applications, high-density photonic integration, metamaterial design, enhanced nonlinear optics, sensing etc. In the current thesis work, we focus on experimental fabrication and characterization of planar plasmonic metamaterials and waveguide structures. The samples are fabricated based on the generic electron beam lithography and characterizations are done with our home-made setups. Mastering and refinement of fabrication techniques as well as setting up the characterization tools have constituted as a majorpart of the thesis work. In particular, we experimentally realized a plasmonic absorber based on a 2D honeycomb array of gold nano-disks sitting on top of a reflector through a dielectric spacer. The absorber not only exhibits an absorption peak which is owing to localized surface plasmon resonance and is insensitive to incidence’s angle or polarization, but also possesses an angle- and polarization-sensitive high-order absorption peak with a narrow bandwidth. We also demonstrated that the strong light absorption in such plasmonic absorbers can be utilized to photothermally re-condition the geometry of gold nanoparticles. The nearly perfect absorption capability of our absorbers promises a wide range of potential applications, including thermal emitter, infrared detectors, and sensors etc. We also fabricated a plasmonic strip waveguide in a similar metal-insulator-metal structure. The strip waveguide has a modal confinement slightly exceeding that of the so-called plasmonic slot waveguide. We further thermally annealed the waveguide. It is observed that the propagation loss at 980 nm has been decreased significantly,which can be attributed to the improvement in gold quality after thermal annealing.

  • 17.
    Chen, Yiting
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Honeycomb-lattice plasmonic absorbers at NIR: anomalous high-order resonance2013In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 18, p. 20873-20879Article in journal (Refereed)
    Abstract [en]

    We design, fabricate and characterize a plasmonic honeycomb lattice absorber with almost perfect absorption at 1140 nm over a wide incident angle range. This absorber also possesses a narrow-band, angle-and polarization-dependent high-order resonance in the short-wavelength range, with a bandwidth of 19 nm and angle sensitivity of 3 nm per degree. The nature of this high-order absorption band is analyzed through finite-element simulations. We believe it is due to Bragg coupling of the incident light to the backward-propagating surface plasmon polariton through the periodic modulation of the structure. Such fine absorption bands can find applications in plasmonic sensors and spectrally selective thermal emitters.

  • 18.
    Chen, Yiting
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Influence of latticestructure on metal-insulator-metal plasmonic absorbersManuscript (preprint) (Other academic)
  • 19.
    Chen, Yiting
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China .
    Metal-insulator-metal plasmonic absorbers: influence of lattice2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 25, p. 30807-30814Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate three kinds of metal-insulator-metal based plasmonic absorbers consisting of arrays of gold nanodisks distributed in different lattices, including square, triangular and honeycomb lattices. It's found that resonances originated from localized surface plasmon undergo little changes with respect to different lattice distributions of the nanodisks. The interparticle coupling results in a minor bandwidth broadening of the fundamental mode. Different from square-and triangular-lattice absorbers, honeycomb-lattice absorber possesses a unique red-shifting (with respect to incident angles) narrow-band high-order mode, which originates from coupling of incident light to propagating surface plasmon polariton (SPP) waves. Similar high-order mode can also be generated in square-lattice absorber by increasing the period so that a smaller reciprocal lattice vector can be introduced to excite the SPP mode. Furthermore, we show that two types of resonances can interact and create Fano-type resonances. The simulation results agree well with the experimental results. (C) 2014 Optical Society of America

  • 20.
    Chen, Yiting
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Xi
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Plasmonic analog of microstrip transmission line and effect of thermal annealing on its propagation loss2013In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 2, p. 1639-1644Article in journal (Refereed)
    Abstract [en]

    We fabricated a plasmonic analog of the microwave microstrip transmission line and measured its propagation loss before and after thermal annealing. It is found that its propagation loss at 980 nm wavelength can be reduced by more than 50%, from 0.45 to 0.20 dB/μm, after thermal annealing at 300 °C. The reduction in loss can be attributed to the improved gold surface condition and probably also to the change in the metal's inner structure. Less evident loss reduction is noticed at 1550 nm, which is owing to extremely small portion of the modal electric field located in the metal regions at this wavelength.

  • 21. da Silva, Edson P.
    et al.
    Borkowski, Robert
    Preussler, Stefan
    Schwartau, Fabian
    Gaiarin, Simone
    Olmedo, Miguel I.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Vedadi, Armand
    Piels, Molly
    Galili, Michael
    Guan, Pengyu
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Bres, Camille-Sophie
    Schneider, Thomas
    Oxenlowe, Leif K.
    Zibar, Darko
    Combined Optical and Electrical Spectrum Shaping for High-Baud-Rate Nyquist-WDM Transceivers2016In: IEEE Photonics Journal, ISSN 1097-5764, E-ISSN 1943-0655, Vol. 8, no 1, article id 7801411Article in journal (Refereed)
    Abstract [en]

    We discuss the benefits and limitations of optical time-division multiplexing (OTDM) techniques based on the optical generation of a periodic train of sinc pulses for wavelength-division multiplexing (WDM) transmission at high baud rates. It is shown how the modulated OTDM spectrum bandwidth is related to the optical comb parameters and the pulse shaping of the modulating waveforms in the electrical domain. Such dependence may result in broadening of the modulated spectra, which can degrade the performance of Nyquist-WDM systems due to interchannel crosstalk penalties. However, it is shown and experimentally demonstrated that the same technique of optical pulse train generation can be allied with digital pulse shaping to improve the confinement of the modulated spectrum toward the Nyquist limit independently of the number of OTDM tributaries used. To investigate the benefits of the proposed approach, we demonstrate the first WDM Nyquist-OTDM signal generation based on the periodic train of sinc pulses and electrical spectrum shaping. Straight line transmission of five 112.5-Gbd Nyquist-OTDM dual-polarization quadrature phase-shift keying (QPSK) channels is demonstrated over a dispersion uncompensated link up to 640 km, with full-field coherent detection at the receiver. It is shown that such a design strategy effectively improves the spectral confinement of the modulated OTDM signal, providing a minimum intercarrier crosstalk penalty of 1.5 dB in baud-rate-spaced Nyquist-WDM systems.

  • 22.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Near-Field Radiative Heat Transfer between Plasmonic Nanostructures2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Radiative heat transfer (RHT) due to coupled electromagnetic near field scan significantly exceed that dictated by Planck’s law. Understanding such phenomenon is not only of fundamental scientific interest, but also relevant to a broad range of applications especially connected to nanotechnologies.This dissertation elaborates, through a scattering approach based on the rigorous coupled wave analysis method, how plasmonic nanostructures can tame the near-field RHT between two bodies. The transmission-factor spectra are corroborated by photonic band diagrams computed using a finite element method. The main work begins by showing that the phenomenon of spoofsurface plasmon polariton (SSPP) guided on grooved metal surfaces can play a similar role as surface phonon polariton in enhancing the RHT between two closely placed plates. Since dispersions of SSPPs especially their resonance frequencies can be engineered through geometrical surface profiling,one has great freedom in tailoring spectral properties of near-field RHT. Further enhancement of RHT can be achieved through techniques like filling of dielectrics in grooves or deploying supercells. A thorough study of RHT betweentwo 1D or 2D grooved metal plates confirms super-Planckian RHT at near-field limit, with 2D grooved metal plates exhibiting a superior frequency selectivity. We also present RHT with a more exotic type of plasmonic nanostructures consisting of profile-patterned hyperbolic metamaterial arrays, and show that with such plasmonic nanostructures one can achieve an ultrabroadband super-Planckian RHT.

  • 23.
    Dai, Jin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ding, Fei
    Bozhevolnyi, Sergey I.
    Centre for Nano Optics, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ultrabroadband Super-Planckian Radiative Heat Transfer with Profile-Patterned Hyperbolic MetamaterialManuscript (preprint) (Other academic)
  • 24.
    Dai, Jin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dyakov, Sergey A.
    Bozhevolnyi, Sergey I.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Near-field radiative heat transfer between metasurfaces: A full-wave study based on two-dimensional grooved metal plates2016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 12, article id 125431Article in journal (Refereed)
    Abstract [en]

    Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two two-dimensional grooved metal plates by a full-wave scattering approach. The enhancement originates from both transverse-magnetic spoof surface-plasmon polaritons and a series of transverse-electric bonding-and anti-bonding-waveguide modes at surfaces. The RHT spectrum is frequency selective and highly geometrically tailorable. Our simulation also reveals thermally excited nonresonant surface waves in constituent metallic materials may play a prevailing role for RHT at an extremely small separation between two metal plates, rendering metamaterial modes insignificant for the energy-transfer process.

  • 25.
    Dai, Jin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dyakov, Sergey A.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Enhanced near-field radiative heat transfer between corrugated metal plates: Role of spoof surface plasmon polaritons2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 3, article id 035419Article in journal (Refereed)
    Abstract [en]

    We demonstrate with the finite-difference time-domain method that radiative heat transfer between two parallel gold plates can be significantly enhanced by engraving periodic grooves with a subwavelength width on the plate surfaces. The enhancement increases with a decrease in the separation distance at near-field regime and it can be further efficiently improved by having a supercell with multiple grooves with different depths. We attribute this near-field enhancement to coupling of thermally excited spoof surface plasmon polaritons, a type of artificial surface wave inherent to structured metal surfaces [J. B. Pendry, L. Martin-Moreno, and F. J. Garcia-Vidal, Science 305, 847 (2004)]. The frequency-dependent contribution to the heat transfer, or transmission-factor spectrum, is confirmed by calculating the dispersion relation of guided modes by the two parallel corrugated plates through a finite-element method. Especially, the photonic density of states derived from the dispersion relation is found to have excellent agreement to the transmission-factor spectrum.

  • 26. Dai, S.
    et al.
    Zhao, D.
    Li, Q.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou 310027, China .
    Double-sided polarization-independent plasmonic absorber at near-infrared region2013In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 11, p. 13125-13133Article in journal (Refereed)
    Abstract [en]

    A double-sided polarization-independent plasmonic absorber is proposed and numerically investigated. Distinct from previously studied absorbers, it could absorb light incident from both sides of the surface through an ultrathin three-layer metal-insulator-metal nanostructure. Patterned metal particles are adopted instead of metal films in this absorber. It shows a high absorbance over a wide incident-Angle range at near-infrared region. For electromagnetic waves incident from different sides of the structure, the maximum absorption locates at different wavelengths due to asymmetry. The effective medium theory demonstrates that the whole structure exhibits different impedances for both top and bottom incidences. This double-sided-Absorption characteristic could lead to potential applications in thermal emitters, sensing, etc.

  • 27. Ding, Boyang
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Blaikie, Richard J.
    Manipulating light absorption in dye-doped dielectric films on reflecting surfaces2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 21, p. 25965-25975Article in journal (Refereed)
    Abstract [en]

    We experimentally and numerically developed a tunable absorbing nanoscale thin-film system, comprising of dye molecules doped dielectric coatings on reflecting surfaces, the absorption behaviors of which can be flexibly tuned by adjusting the system parameters, i.e. the coating thickness and the doping concentration of dye molecules. Specifically, with appropriate system parameters, our absorbing thin-film system exhibits very directional and polarization dependent absorption properties, which can be significantly altered if applied with different parameters. Calculations demonstrate the unique absorption behaviors are a result of coupling between molecular absorption and Fabry-Perot resonances in the thin-film cavity. In addition, we theoretically show that both the spectral and directional range of the absorption in the thin-film system can be intentionally regulated by doping dyes with different absorption band and setting proper excitation conditions of Fabry-Perot resonances.

  • 28.
    Dou, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Lou, Fei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Boström, Mathias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Brevik, Iver
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Casimir quantum levitation tuned by means of material properties and geometries2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 20, p. 201407-Article in journal (Refereed)
    Abstract [en]

    The Casimir force between two surfaces is attractive in most cases. Although stable suspension of nano-objects has been achieved, the sophisticated geometries make them difficult to be merged with well-established thin film processes. We find that by introducing thin film surface coating on porous substrates, a repulsive to attractive force transition is achieved when the separations are increased in planar geometries, resulting in a stable suspension of two surfaces near the force transition separation. Both the magnitude of the force and the transition distance can be flexibly tailored though modifying the properties of the considered materials, that is, thin film thickness, doping concentration, and porosity. This stable suspension can be used to design new nanodevices with ultralow friction. Moreover, it might be convenient to merge this thin film coating approach with micro- and nanofabrication processes in the future.

  • 29. Du, Kaikai
    et al.
    Li, Qiang
    Zhang, Weichun
    Yang, Yuanqing
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Wavelength and Thermal Distribution Selectable Microbolometers Based on Metamaterial Absorbers2015In: IEEE Photonics Journal, ISSN 1943-0655, Vol. 7, no 3, article id 6800908Article in journal (Refereed)
    Abstract [en]

    An uncooled microbolometer based on metamaterial absorbers is investigated. The absorption peak reaches 90%, and the peak wavelength can be tailored from 2.4 to 10.2 mu m with corresponding bandwidth varying from 0.5 to 1.5 mu m by tuning the geometric parameters of the absorbers, covering two atmosphere windows (3-5 mu m and 8-14 mu m). The thermal distribution in the microbolometer can be adjusted to realize a strong thermal response. In the given situation with a pixel size of 25.07 mu m, the temperature response of the detector reaches 1.3 K. The microbolometer can be potentially used in thermal imaging at selected wavelengths in the mid-infrared and far-infrared regimes.

  • 30.
    Dyakov, Sergey A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, M.
    Thermal radiation dynamics in two parallel plates: The role of near field2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 4, p. 045414-Article in journal (Refereed)
    Abstract [en]

    The temperature dynamics of the radiative heat propagation in a multilayer structure is theoretically treated with a formalism combining the scattering matrix and Green's-functions methods. The time evolution of the temperature of parallel plates of silicon carbide in vacuum is simulated for different interplate distances and thicknesses of plates. The characteristic radiative heat exchange time and temperature of the plates at stationary state are determined from the time evolutions. The threshold interplate distance which separates heating and cooling regimes for the sink plate is found. We show that the variation of the interplate distance allows us to control the relaxation processes in the system of absorber and emitter.

  • 31.
    Dyakov, Sergey A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Dai, Jin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Near field thermal memory based on radiative phase bistability of VO22015In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 48, no 30, article id 305104Article in journal (Refereed)
    Abstract [en]

    We report the concept of a near-field memory device based on the radiative bistability effect in the system of two closely separated parallel plates of SiO2 and VO2 which exchange heat by thermal radiation in vacuum. We demonstrate that the VO2 plate, having metal-insulator transition at 340 K, has two thermodynamical steady-states. One can switch between the states using an external laser impulse. We show that due to near-field photon tunneling between the plates, the switching time is found to be only 5 ms which is several orders lower than in case of far field.

  • 32.
    Dyakov, Sergey
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Trinity College Dublin.
    Baldycheva, A.
    Perova, T. S.
    Li, G. V.
    Astrova, E. V.
    Gippius, N. A.
    Tikhodeev, S. G.
    Surface states in the optical spectra of two-dimensional photonic crystals with various surface terminations2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 11, p. 115126-1151268Article in journal (Refereed)
    Abstract [en]

    Reflection and transmission spectra of two-dimensional photonic crystal slabs, fabricated by photoelectrochemical etching of deep macropores and trenches in Si, are investigated theoretically and experimentally. It is shown that the presence of an unstructured silicon interfacial layer between the air and the photonic crystal structure can give rise to surface (Tamm) states within the TE and TM photonic stop bands. In the presence of roughness of inner surfaces of air pores, the surface states show up as dips within the stop bands in the reflection spectrum. The calculated electromagnetic near-field distribution demonstrates the vortices between the upper pores at the frequency of the surface mode. The experimental reflection and transmission spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.

  • 33.
    Dyakov, Sergey
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Trinity College Dublin.
    Perova, T. S.
    Miao, C. Q.
    Xie, Y. -H
    Cherevkov, S. A.
    Baranov, A. V.
    Influence of the buffer layer properties on the intensity of Raman scattering of graphene2013In: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 44, no 6, p. 803-809Article in journal (Refereed)
    Abstract [en]

    Using a model of oscillating dipoles, we simulate the intensity of the G-band in the Raman signal from structures consisting of graphene, separated by an arbitrary buffer layer from a substrate. It is found that a structure with an optimized buffer layer refractive index and thickness exhibits a Raman signal which is nearly 50 times more intense than that from the same structure with a non-optimized buffer layer. The theoretical simulations are verified by Raman measurements on structures consisting of a layer of graphene on SiO2 and Al2O3 buffer layers. The optical contrast of the single graphene layer is calculated for an arbitrary buffer layer. It was found that both the Raman intensity and optical contrast can be maximized by varying the buffer layer thickness.

  • 34.
    Dyakov, Sergey
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Skolkovo Institute of Science and Technology, Russia.
    Zhigunov, D. M.
    Marinins, Aleksandrs
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Shcherbakov, M. R.
    Fedyanin, A. A.
    Vorontsov, A. S.
    Kashkarov, P. K.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, China.
    Zacharias, M.
    Tikhodeev, S. G.
    Gippius, N. A.
    Optical properties of silicon nanocrystals covered by periodic array of gold nanowires2016In: Physical Review B, ISSN 2469-9950, Vol. 93, no 20, article id 205413Article in journal (Refereed)
    Abstract [en]

    Extinction and photoluminescence spectra are experimentally and theoretically studied for a periodic array of gold nanowires deposited on top of a dielectric substrate containing silicon nanocrystals. Quasiguided modes are observed in the substrate resulting in modification of optical properties of silicon nanocrystals. Our calculations of extinction and photoluminescence spectra are in good agreement with experimental results. The periodicity provides a powerful tool for achieving a high photoluminescence outcoupling efficiency of silicon nanocrystals.

  • 35. Favier, Maxime
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Tailored polarization eigenstates of liquid crystal SLM to generate Laguerre-Gaussian beams2014In: Proceedings - 2014 International Conference Laser Optics, LO 2014, 2014Conference paper (Refereed)
    Abstract [en]

    We use an SLM to generate laser beams of variable orbital angular momentum, also referred as Laguerre-Gaussian beams. Input beam polarization should match local birefringence of each pixel of the SLM. We identify the beam polarization eigenstates allowing generate L-G beams of different order owing to matching variable birefringence of separate pixels. Experimental results demonstrate an excellent agreement with simulations.

  • 36. Gaiarin, S.
    et al.
    Pang, X.
    Ozolins, O.
    Jones, R. T.
    Da Silva, E. P.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, G.
    Zibar, D.
    High speed PAM-8 optical interconnects with digital equalization based on neural network2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
    Abstract [en]

    We experimentally evaluate a high-speed optical interconnection link with neural network equalization. Enhanced equalization performances are shown comparing to standard linear FFE for an EML-based 32 GBd PAM-8 signal after 4-km SMF transmission.

  • 37.
    Gelzinyte, Kristina
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Vilnius State Univ, Inst Appl Res, Lithuania.
    Ivanov, Ruslan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zhao, Y.
    Becerra, D. L.
    Nakamura, S.
    DenBaars, S. P.
    Speck, J. S.
    High spatial uniformity of photoluminescence spectra in semipolar (20(2)over-bar1) plane InGaN/GaN quantum wells2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 2, p. 023111-Article in journal (Refereed)
    Abstract [en]

    Scanning near-field optical spectroscopy was applied to study spatial variations of emission spectra at room temperature in semipolar (20 (2) over bar1) InxGa(1-x)N/GaN single quantum wells (QWs) for 0:11 <= x <= 0:36. Photoluminescence (PL) was found to be highly uniform, with peak wavelength deviations and peak intensity deviations divided by average values in the range of 6-12 meV and 0.03-0.07, respectively. Near-field maps of PL parameters showed large, similar to 5 to 10 mu m size areas of similar values, as opposed to 100 nm scale variations, often reported for InGaN QWs. The near-field PL spectra were found to broaden with increasing InN molar fraction. In the low In content QWs, the broadening is primarily determined by the random cation distribution, while for larger InN molar fractions 10 nm scale localization sites with increasingly deeper band potentials are suggested as the linewidth broadening cause.

  • 38. Gong, H.
    et al.
    Chen, Xi
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qu, Y.
    Li, Q.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, M.
    Photothermal Switching Based on Silicon Mach-Zehnder Interferometer Integrated with Light Absorber2016In: IEEE Photonics Journal, ISSN 1097-5764, E-ISSN 1943-0655, Vol. 8, no 2, article id 7456199Article in journal (Refereed)
    Abstract [en]

    We present an all-optical switch based on photothermal effects in a silicon Mach-Zehnder interferometer (MZI) integrated with a light absorber. The metal-insulator-metal light absorber located near the longer arm of the asymmetric MZI efficiently converts infrared light to heat. Pumped by a continuous-wave 1064-nm laser, the spectral transmittance of the fully etched strip waveguide (half-etched rib waveguide) MZI can be tuned with an efficiency of 38 pm/mW (98.5 pm/mW). Dynamic switching experiments show that the rise/fall time constant of the output probe light is 11.45/10.98 μs (8.25/7.13 μs) for the fully etched (half-etched) MZI.

  • 39. Gong, Hanmo
    et al.
    Yang, Yuanqing
    Chen, Xingxing
    Zhao, Ding
    Chen, Xi
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Li, Qiang
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Zhejiang University, Hangzhou, China.
    Gold nanoparticle transfer through photothermal effects in a metamaterial absorber by nanosecond laser2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 6080-Article in journal (Refereed)
    Abstract [en]

    A non-complicated, controllable method of metallic nanoparticle fabrication at low operating light power is proposed. The method is based on laser-induced forward transfer, using a metamaterial absorber as the donor to significantly enhance the photothermal effect and reduce the operating light fluence to 35 mJ/cm(2), which is much lower than that in previous works. A large number of metallic nanoparticles can be transferred by one shot of focused nanosecond laser pulses. Transferred nanoparticles exhibit good size uniformity and the sizes are controllable. The optical properties of transferred particles are characterized by dark-field spectroscopy and the experimental results agree with the simulation results.

  • 40. Guan, Xiaowei
    et al.
    Chen, Pengxin
    Wang, Xiaokun
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Shi, Yaocheng
    Dai, Daoxin
    Ultrasmall Directional Coupler and Disk-resonantor Based on Nano-scale Silicon Hybrid Plasmonic Waveguides2012In: 2012 Asia Communications And Photonics Conference (ACP), 2012, p. AS2H.4-Conference paper (Refereed)
    Abstract [en]

    Nanophotonic integrated devices based on nano-scale silicon hybrid plasmonic waveguides have been demonstrated experimentally, including directional couplers and disk-resonators. The temperature-dependence of the hybrid plasmonic disk-resonators is also characterized.

  • 41. Guan, Xiaowei
    et al.
    Wu, Hao
    Shi, Yaocheng
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Dai, Daoxin
    Ultracompact and broadband polarization beam splitter utilizing the evanescent coupling between a hybrid plasmonic waveguide and a silicon nanowire2013In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 38, no 16, p. 3005-3008Article in journal (Refereed)
    Abstract [en]

    An ultracompact polarization beam splitter (PBS) is proposed based on an asymmetrical directional coupler consisting of a silicon hybrid plasmonic waveguide (HPW) and a silicon nanowire. The widths of the two coupling waveguides are chosen so that the phase-matching condition is satisfied for TE polarization only while the phase mismatch is significant for TM polarization. A sharply bent silicon HPW is connected at the thru port to play the role of polarizer by utilizing its polarization-dependent loss. With the present principle, the designed PBS has a footprint as small as only similar to 1.9 mu m x 3.7 mu m, which is the shortest PBS reported until now, even when large waveguide dimensions (e. g., the waveguide widths w(1,2) = similar to 300 nm and the gap width w(gap) = similar to 200 nm) are chosen to simplify the fabrication process. The numerical simulations show that the designed PBS has a very broad band (similar to 120 nm) with an extinction ratio >12 dB and a large fabrication tolerance to allow a waveguide width variation of similar to 30 nm.

  • 42.
    Hassinen, Timo
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Friberg, Ari T.
    Setala, Tero
    Generation of nearly 3D-unpolarized evanescent optical near fields using total internal reflection2016In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, no 13, p. 2942-2945Article in journal (Refereed)
    Abstract [en]

    We analyze the time-domain partial polarization of optical fields composed of two evanescent waves created in total internal reflection by random electromagnetic beams with orthogonal planes of incidence. We show that such a two-beam configuration enables to generate nearly unpolarized, genuine three-component (3D) near fields. This result complements earlier studies on spectral polarization, which state that at least three symmetrically propagating beams are required to produce a 3D-unpolarized near field. The degree of polarization of the near field can be controlled by adjusting the polarization states and mutual correlation of the incident beams.

  • 43. Hiller, D.
    et al.
    Zelenina, A.
    Gutsch, S.
    Dyakov, Sergey
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Lopez-Conesa, L.
    Lopez-Vidrier, J.
    Estrade, S.
    Peiro, F.
    Garrido, B.
    Valenta, J.
    Korinek, M.
    Trojanek, F.
    Maly, P.
    Schnabel, M.
    Weiss, C.
    Janz, S.
    Zacharias, M.
    Absence of quantum confinement effects in the photoluminescence of Si3N4-embedded Si nanocrystals2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 20, p. 204301-Article in journal (Refereed)
    Abstract [en]

    Superlattices of Si-rich silicon nitride and Si3N4 are prepared by plasma-enhanced chemical vapor deposition and, subsequently, annealed at 1150 degrees C to form size-controlled Si nanocrystals (Si NCs) embedded in amorphous Si3N4. Despite well defined structural properties, photoluminescence spectroscopy (PL) reveals inconsistencies with the typically applied model of quantum confined excitons in nitride-embedded Si NCs. Time-resolved PL measurements demonstrate 10(5) times faster time-constants than typical for the indirect band structure of Si NCs. Furthermore, a pure Si3N4 reference sample exhibits a similar PL peak as the Si NC samples. The origin of this luminescence is discussed in detail on the basis of radiative defects and Si3N4 band tail states in combination with optical absorption measurements. The apparent absence of PL from the Si NCs is explained conclusively using electron spin resonance data from the Si/Si3N4 interface defect literature. In addition, the role of Si3N4 valence band tail states as potential hole traps is discussed. Most strikingly, the PL peak blueshift with decreasing NC size, which is often observed in literature and typically attributed to quantum confinement (QC), is identified as optical artifact by transfer matrix method simulations of the PL spectra. Finally, criteria for a critical examination of a potential QC-related origin of the PL from Si3N4-embedded Si NCs are suggested.

  • 44.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Electro-optic switch based on near-field-coupled quantum dots2014In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 115, no 4, p. 1093-1101Article in journal (Refereed)
    Abstract [en]

    The propagation of exciton polaritons in near-field-coupled quantum-dot (QD) chains is modeled by a density-matrix formalism. It is shown that at least for low-temperature operation it is possible using electronically controlled switching by the quantum-confined Stark effect in such QD chains to rival and outperform room-temperature CMOS electronics in footprint and switch energy, though not in speed.

  • 45.
    Iglesias Olmedo, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Technical University of Denmark (DTU), Denmark .
    Pang, Xiaodan
    RISE ACREO AB.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zibar, D.
    Tafur Monroy, I.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo AB, Sweden.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Digital signal processing approaches for semiconductor phase noise tolerant coherent transmission systems2015In: Proceedings of SPIE - The International Society for Optical Engineering, 2015Conference paper (Refereed)
    Abstract [en]

    We discuss about digital signal processing approaches that can enable coherent links based on semiconductor lasers. A state-of-the art analysis on different carrier-phase recovery (CPR) techniques is presented. We show that these techniques are based on the assumption of lorentzian linewidth, which does not hold for monolithically integrated semiconductor lasers. We investigate the impact of such lineshape on both 3 and 20 dB linewidth and experimentally conduct a systematic study for 56-GBaud DP-QPSK and 28-GBaud DP-16QAM systems using a decision directed phase look loop algorithm. We show how carrier induced frequency noise has no impact on linewidth but a significant impact on system performance; which rises the question on whether 3-dB linewidth should be used as performance estimator for semiconductor lasers.

  • 46.
    Iglesias Olmedo, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark2800 Kgs. Lyngby, Denmark .
    Suhr, Lau
    Prince, Kamau
    Rodes, Roberto
    Mikkelsen, Christian
    Hviid, Erling
    Neumeyr, Christian
    Vollrath, Gunther
    Goobar, Edgard
    Ohlen, Peter
    Monroy, Idelfonso Tafur
    Gigabit Access Passive Optical Network Using Wavelength Division Multiplexing-GigaWaM2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 22Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the research and technical achievements done under the EU project GigaWaM. The goal of this project was to develop a cost-effective solution that can meet the increasing bandwidth demands in access networks. The approach was to use a novel wavelength division multiplexing passive optical network (WDM-PON) architecture that can deliver symmetric 1 Gb/s to 64 users over 20 km standard single mode fiber using the L and C bands for down and upstream, respectively. During the course of the project, a number of key enabling technologies were developed including tunable transceivers, athermal 50 GHz spaced arrayed waveguide grating multiplexer devices, novel hybridization technologies for integration of passive and active electro-optic devices, and system-level algorithms that ensure the quality of service. The outcome of the project proved a reliable, cost-effective, flexible, and upgradable WDM-PON solution, achieving per-user datarates of 2.5 and 10 Gb/s for up and downstream, respectively. The proposed solution is not only suitable for access networks, but also for metro aggregation and mobile backhaul.

  • 47.
    Iglesias Olmedo, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zuo, Tianjian
    Jensen, Jesper Bevensee
    Zhong, Qiwen
    Xu, Xiaogeng
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Monroy, Idelfonso Tafur
    Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 4, p. 798-804Article in journal (Refereed)
    Abstract [en]

    Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion and bandwidth limitations, and reduces the complexity of the transceiver. We report on numerical simulations and experimental demonstrations with capacity beyond 100 Gb/s transmission using a single externally modulated laser. In addition, an extensive comparison with conventional CAP is also provided. The reported experiment uses MultiCAP to achieve 102.4 Gb/s transmission, corresponding to a data payload of 95.2 Gb/s error free transmission by using a 7% forward error correction code. The signal is successfully recovered after 15 km of standard single mode fiber in a system limited by a 3 dB bandwidth of 14GHz.

  • 48.
    Islam, A. B. M. Hamidul
    et al.
    KTH, School of Information and Communication Technology (ICT). Hanyang University, South Korea .
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Operation of low driving voltage cascaded modulator over non-cascaded modulator for 4 dB extinction ratio at 100 giga bit per second (Gbps)2014In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 125, no 22, p. 6761-6764Article in journal (Refereed)
    Abstract [en]

    This paper describes improved results when comparing cascaded traveling wave electro absorption modulator (TWEAM) to non-cascaded TWEAM by simulation. Large signal modeling is used for both types of modulators to achieve 4 and 10 dB extinction ratios (ERs) with flat frequency response for applications in short distance as well as long distance optical fiber communication. To obtain 4 and 10 dB ERs with 110 GHz 3 dB bandwidth, a cascaded TWEAM requires 0.4V peak to peak (Vp-p) and 1 Vp-p input driving voltages respectively. A non-cascaded TWEAM requires about two times the input driving voltage compared to the cascaded modulator to achieve the same values of ER and 3 dB bandwidth. Both modulators have been simulated with the same bias and also use the same circuit parameters except for the total active segment lengths (1 and 0.5 mm for cascaded and non-cascaded modulator respectively) and microstrip lengths to obtain the same ERs and 3 dB bandwidths.

  • 49.
    Ismail, Nur
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Calil Kores, Cristine
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    The Fabry-Pérot resonator: Spectral line shapes, generic and related Airy distributions, linewidths, finesses, and performance at low or frequency-dependent reflectivity2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 15, p. 16366-16389Article in journal (Refereed)
    Abstract [en]

    We systematically characterize the Fabry-Pérot resonator. We derive the generic Airy distribution of a Fabry-Pérot resonator, which equals the internal resonance enhancement factor, and show that all related Airy distributions are obtained by simple scaling factors. We analyze the textbook approaches to the Fabry-Pérot resonator and point out various misconceptions. We verify that the sum of the mode profiles of all longitudinal modes is the fundamental physical function that characterizes the Fabry-Pérot resonator and generates the Airy distribution. Consequently, the resonator losses are quantified by the linewidths of the underlying Lorentzian lines and not by the measured Airy linewidth. Therefore, we introduce the Lorentzian finesse which provides the spectral resolution of the Lorentzian lines, whereas the usually considered Airy finesse only quantifies the performance of the Fabry-Pérot resonator as a scanning spectrometer. We also point out that the concepts of linewidth and finesse of the Airy distribution of a Fabry-Pérot resonator break down at low reflectivity. Furthermore, we show that a Fabry-Pérot resonator has no cut-off resonance wavelength. Finally, we investigate the influence of frequency-dependent mirror reflectivities, allowing for the direct calculation of its deformed mode profiles.

  • 50.
    Ivanov, Ruslan
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Zhao, Y.
    Becerra, D. L.
    Nakamura, S.
    DenBaars, S. P.
    Speck, J. S.
    Impact of carrier localization on radiative recombination times in semipolar (2021) plane InGaN/GaN quantum wells2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 21, article id 211109Article in journal (Refereed)
    Abstract [en]

    Semipolar (20 (2) over bar1) plane In,Ga1-xN quantum wells (QWs) of varying alloy composition were studied by time-resolved photoluminescence. A large difference in effective radiative lifetimes. from sub-ns for x = 0.11 to similar to 30 ns for x approximate to 0.35 was found. This effect is attributed to different properties of carrier localization. In low In content QWs. recombination at extended states with short recombination times is prevalent. In QWs with a high In content, the lifetimes are increased by localization of electrons and holes at separate sites. The zigzag shape of the QW interfaces and the resulting in-plane electric field are proposed as the cause for the separate electron and hole localization.

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