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  • 51. Ge, Xiaochen
    et al.
    Shi, Yaocheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Ultra-compact channel drop filter based on photonic crystal nanobeam cavities utilizing a resonant tunneling effect2014In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 24, p. 6973-6976Article in journal (Refereed)
    Abstract [en]

    The design, fabrication, and characterization of a compact photonic crystal nanobeam drop filter based on the tunneling effect of the degenerate modes are presented. The degeneracy was achieved by tuning the coupling distance between the nanobeam and input/output waveguides. The tunneling effect of degenerate resonances with different symmetries has been verified experimentally. Channel drop filters with an extinction ratio larger than 10 dB and a quality factor of similar to 5000 have been experimentally demonstrated.

  • 52. Gong, Chensheng
    et al.
    Zhang, Jianhao
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 24, p. 5098-5101Article in journal (Refereed)
    Abstract [en]

    Unidirectional optical manipulation, especially the coupling from a vertical light beam to a waveguide unidirectionally, is desirable in photonic integration. We first propose a hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength, a periodic plasmonic metasurface composed of metal-insulator-metal unit cells is used for phase matching. Three designs are given for devices working around wavelengths 0.85, 1.31, and 1.55 mu m. The simulated coupling efficiencies are all around 70%, and the 1 dB coupling bandwidths are 29, 82, and 105 nm, respectively. Our approach paves the way for the applications of optical metasurfaces to planar lightwave circuits. (C) 2017 Optical Society of America

  • 53.
    Grishin, Alexander M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Khartsev, Sergey I.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Luminescence in epitaxial Er-doped LiNbO3 films2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 3, p. 419-421Article in journal (Refereed)
    Abstract [en]

    Epitaxial Er-doped LiNbO3 films were pulsed-laser-deposited onto c-cut sapphire. Wavelength dispersion of the refractive index and the extinction coefficient was obtained by fitting the experimental transmittance spectrum to the Swanepoel formula and microscopic theory, which accounts for two resonance transitions in the electric dipole approximation. Strong room temperature luminescence was observed under 514.5 nm Ar-laser pumping. Two-lifetime (3.0 and 6.0 ms) luminescent decay is characteristic for the lasing I-4(13/2) -> I-4(15/2) transition in Er:LiNbO3 films.

  • 54. 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.

  • 55. Gösch, Michael
    et al.
    Blom, Hans
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rigler, Rudolf
    Anderegg, Sylvain
    Lasser, Theo
    Magnusson, Anders
    Hård, Sverker
    Multi-focal dual-color cross-correlation spectroscopy of single biomolescules using diffractive-optical-elements2003In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed)
  • 56. Hansson, B. T.
    et al.
    Friberg, Ari T.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Eye-safe actively Q-switched microchip laser with an electro-absorbing semiconductor modulator2001In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 26, no 14, p. 1057-1059Article in journal (Refereed)
    Abstract [en]

    We present what we believe to be the first actively Q-switched monolithic microchip laser with a wavelength of 1.55 mum that uses an electro-absorbing semiconductor modulator. At an absorbed pump power of 130 mW and a switching voltage of 2.2 V, the laser produces 470-nJ pulses at a repetition rate of 10 kHz. The output is a stable single longitudinal mode with a center wavelength of 1.553 mu tm, and the transverse beam profile is close to an ideal Gaussian, with an M-2 value of 1.15.

  • 57. Hao, Jiaming
    et al.
    Qiu, Cheng-Wei
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Zouhdi, Said
    Design of an ultrathin broadband transparent and high-conductive screen using plasmonic nanostructures2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 23, p. 4955-4957Article in journal (Refereed)
    Abstract [en]

    In this Letter, we present a new type of ultrathin antireflection transparent and high-conductive screen based on plasmonic nanostructures that does not suffer from high loss and thickness coating and also can be used as good conductive material due to super electrical conductivity of the component (noble metal). Low reflection and greatly enhanced transmissions over a broad spectral range are observed at optical telecommunication frequencies in arbitrary polarizations. The performance is almost insensitive of the angle of incidence.

  • 58.
    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.

  • 59. Hassinen, Timo
    et al.
    Tervo, Jani
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Cross-spectral purity of electromagnetic fields2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 24, p. 3866-3868Article in journal (Refereed)
    Abstract [en]

    We extend Mandel's scalar-wave concept of cross-spectral purity to electromagnetic fields. We show that in the electromagnetic case, assumptions similar to the scalar cross-spectral purity lead to a reduction formula, analogous with the one introduced by Mandel. We also derive a condition that shows that the absolute value of the normalized zeroth two-point Stokes parameter of two cross-spectrally pure electromagnetic fields is the same for every frequency component of the field. In analogy with the scalar theory we further introduce a measure of the cross-spectral purity of two electromagnetic fields, namely, the degree of electromagnetic cross-spectral purity.

  • 60. Hellstrom, J.
    et al.
    Karlsson, G.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Optical parametric amplification in periodically poled KTiOPO4 seeded by an Er-Yb: glass microchip laser2001In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 26, no 6, p. 352-354Article in journal (Refereed)
    Abstract [en]

    An optical parametric amplifier based on periodically poled KTiOPO4 was used to generate 3-ns pulses at 1.544 mum. The device was pumped by a Q-switched Nd:YAG laser, and the signal output-pulse energy reached 71 muJ; the maximum gain was 66 dB. The seed source was an Er-Yb:glass microchip laser. A theoretical fit to experimental data gave an effective nonlinear coefficient of 9.7 pm/V, close to the highest values reported for periodically poled KTiOPO4. Furthermore, the broad parametric gain observed could be used for broadband pulse amplification.

  • 61. Hellstrom, J.
    et al.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Karlsson, H.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    High-power optical parametric oscillation in large-aperture periodically poled KTiOPO42000In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 25, no 3, p. 174-176Article in journal (Refereed)
  • 62.
    Hellström, J.
    et al.
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Karlsson, Håkan
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Efficient nanosecond optical parametric oscillators based on periodically poled KTiOPO4, emitting in 1.8-2.5 µm spectral region1999In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 24, p. 1233-1235Article in journal (Refereed)
    Abstract [en]

    The use of periodically poled KTiOPO4 as a gain medium in efficient nanosecond optical parametric oscillators pumped by a flash-lamp-pumped 𝑄‐switched Nd:YAG laser is demonstrated. Parametric radiation in the 1.8–2.5‐µm spectral region was achieved when the crystal temperature was tuned from 10 to 100 °C. A maximum total output energy of 1.8 mJ was obtained at a pump level of 3.5 mJ. Stable operation was achieved, with conversion efficiencies reaching 50%. No gray tracking or laser damage was observed, even for pump intensities of 450 MW/cm2.

  • 63.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Henricsson, Hanna
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bünting, Udo
    Vision Crystal Technology AG, Germany.
    Haussman, Dirk
    Vision Crystal Technology AG, Germany.
    Polarization-tunable Yb:KGW laser based on internal conical refraction2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 19, p. 2783-2785Article in journal (Refereed)
    Abstract [en]

    Using internal conical refraction, we demonstrate an Yb:KGW laser where the polarization state can be arbitrarily altered without any additional cavity components. The extinction ratio can also be altered between 1:1 and 40:1. The maximum output power achieved was 8.6 W at a slope efficiency of 60.5% with respect to incident pump power. This equals the power performance of a standard Yb:KGW laser used for reference.

  • 64.
    Hellström, Jonas
    et al.
    KTH, School of Engineering Sciences (SCI).
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI).
    Karlsson, Håkan
    KTH, School of Engineering Sciences (SCI).
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI).
    Efficient nanosecond optical parametric oscillatorsbased on periodically poled KTPemitting in the 1.8–2.5-mm spectral region1999In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 24, p. 1233-1235Article in journal (Refereed)
  • 65. Henriksson, Markus
    et al.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 μm source2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, p. 1878-1880Article in journal (Refereed)
    Abstract [en]

    A tandem optical parametric oscillator (OPO) is used to convert radiation from 1.064 μm to the mid-infrared. Spectral bandwidth narrowing close to 80 times compared with a conventional cavity was achieved by using a bulk Bragg grating as an outcoupler in a near-degenerate periodically poled KTiOPO4 OPO. The narrowed 2008 nm radiation was subsequently used for pumping the ZnGeP2 OPO, which was tunable between 3.3 and 5.2 μm. Pulse energies of 170 μJ and pump depletion close to 70% were obtained in the ZnGeP2 OPO. To our knowledge this is the first time the output from a near-degenerate type I PPKTP OPO has been used for ZnGeP2 OPO pumping.

  • 66.
    Hertz, Hans M.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Larsson, Jakob C.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Ulf
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Larsson, Daniel H.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Laboratory x-ray fluorescence tomography for high-resolution nanoparticle bio-imaging2014In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 9, p. 2790-2793Article in journal (Refereed)
    Abstract [en]

    We demonstrate that nanoparticle x-ray fluorescence computed tomography in mouse-sized objects can be performed with very high spatial resolution at acceptable dose and exposure times with a compact laboratory system. The method relies on the combination of the 24 keV line-emission from a high-brightness liquid-metal-jet x-ray source, pencil-beam-forming x-ray optics, photon-counting energy-dispersive detection, and carefully matched (Mo) nanoparticles. Phantom experiments and simulations show that the arrangement significantly reduces Compton background and allows 100 mu m detail imaging at dose and exposure times compatible with small-animal experiments. The method provides a possible path to in vivo molecular x-ray imaging at sub-100 mu m resolution in mice.

  • 67.
    Iyer, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari. T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Linear birefringence in split-ring resonators2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 11, p. 2043-2045Article in journal (Refereed)
    Abstract [en]

    We study polarization-dependent transmission of light through arrays of single-slit split-ring resonator (SSRR) based systems at normal incidence using finite integration time domain (FITD) and finite element methods (FEM). It is found that a conventional planar array of SSRRs acts as an effective optical wave plate at certain polarizations of incident light. The effect is attributed to the intrinsic linear birefringence of individual SSRRs. A comparison is made with other split-ring resonator-based systems exhibiting wave-plate-like properties due to inter-SSRR coupling.

  • 68.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrowband and tunable ring optical parametric oscillator with a volume Bragg grating2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 22, p. 3278-3280Article in journal (Refereed)
    Abstract [en]

    We demonstrate a tunable nanosecond optical parametric oscillator with a narrowed signal spectrum. This was done by use of a volume Bragg grating based retrorefiector, which makes the tuning simple and yields a compact design. Using periodically poled KTiOPO4 as the nonlinear medium, we generated 0.42 mJ of signal energy at 760 nm with a tuning range of 5 nm (2.6 THz) and a bandwidth of 0.25nm (130 GHz) when the oscillator was pumped at 532 nm with 1.3 mJ of energy.

  • 69.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tunable single-longitudinal-mode ErYb:glass laser locked by a bulk glass Bragg grating2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, no 11, p. 1663-1665Article in journal (Refereed)
    Abstract [en]

    A single-longitudinal-mode Er-Yb:glass laser with a linewidth of 90 kHz is demonstrated by locking the laser wavelength to 1552.6 nm with a bulk glass Bragg grating. Using a piezoelectric actuator, the wavelength could be tuned over a range of 0.25 nm (31 GHz) in steps of 17 pro (2.1 GHz), with an output power of a few milliwatts.

  • 70.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Rotari, Eugeniu
    Smirnov, Vadim
    Glebov, Leonid
    Tunable narrowband optical parametric oscillator using a transversely chirped Bragg grating2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 4, p. 449-451Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel technique for locking and tuning of a near-degenerate nanosecond optical parametric oscillator (OPO) using a transversely chirped volume Bragg grating. When the grating was translated, the OPO signal wavelength could be tuned from 1011 to 1023 nm (3.5 THz). The OPO was based on a periodically poled KTiOPO4 as a nonlinear crystal and was pumped at 532 run with up to 1.9 mJ of energy. The generated signal at an energy of 0.37 mJ had a bandwidth of 0.50 nm and a suppression of broadband background of >30 dB. The demonstrated technique is widely applicable for the construction of narrowband tunable sources. 0 2009 Optical Society of America

  • 71.
    Jacobsson, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrowband bulk Bragg grating optical parametric oscillator2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 17, p. 2281-2283Article in journal (Refereed)
    Abstract [en]

    A narrowband, pulsed optical parametric oscillator (OPO) whose output coupler is a bulk glass Bragg grating is demonstrated. The OPO is based on periodically poled KTiOPO4 and is pumped by a pulsed, frequency-doubled Nd:YAG laser at 532 nm, generating a signal at 975 nm with a total efficiency of 35%. This novel and compact device shows a spectral bandwidth of 0.16 nm (50 GHz), a decrease by a factor of 20 compared with that when a conventional mirror is used. By using a folded cavity, we demonstrate tunable radiation with a tuning range of 60 nm and maintained spectral bandwidth.

  • 72.
    Jalali-Roudsar, Amir Abbas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Faraday rotation in a two-dimensional photonic crystal with magneto-optic defect2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 10, p. 1213-1215Article in journal (Refereed)
    Abstract [en]

    We study the magneto-optic (MO) Faraday rotation in a two-dimensional square-lattice photonic crystal with a central MO defect layer in the optical wavelength range. We show that when a TM plane wave is incident upon a photonic crystal, an enhancement of Faraday rotation takes place in a region where a resonance peak appears in the photonic bandgap. In this region the mode conversion is high.

  • 73.
    Jelger, Pär
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Efficient skew-angle cladding-pumped tunable narrow-linewidth Yb-doped fiber laser2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 24, p. 3501-3503Article in journal (Refereed)
    Abstract [en]

    A skew-angle cladding-pumped tunable Yb-doped fiber laser is presented. The laser was tunable over more than 30 nm, from 1022 to 1055 nm, by employing a volume Bragg grating in a retroreflector configuration as one of the cavity delimiters. Output powers in excess of 4.3 W were recorded with a spectral bandwidth of 5 GHz and an M2 value below 1.3 over the whole tuning range.

  • 74.
    Jelger, Pär
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Improved photodarkening resistivity in ytterbium-doped fiber lasers by cerium codoping2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 8, p. 1285-Article in journal (Refereed)
    Abstract [en]

    We show that the photodarkening resistivity of ytterbium-doped fiber lasers can be greatly improved by cerium codoping. It is suggested that the coexistence of the redox couple Ce3+/Ce4+ in the glass provides means for trapping both hole- and electron-related color centers that are responsible for the induced optical losses in Yb-doped fiber lasers.

  • 75. Karim, F.
    et al.
    Bora, T.
    Chaudhari, M. B.
    Habib, K.
    Mohammed, W. S.
    Dutta, Joydeep
    Asian Institute of Technology (AIT), Thailand; Sultan Qaboos University, Oman.
    Optical fiber-based sensor for in situ monitoring of cadmium sulfide thin-film growth2013In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 38, no 24, p. 5385-5388Article in journal (Refereed)
    Abstract [en]

    This work presents a scheme for in situ monitoring of thin-film growth. A fiber-optic sensor based on Fabry-Perot interferometric technique has been established for the first time to monitor in situ growth of thin films. This was applied for determining thickness of cadmium sulfide (CdS) thin films during growth. The fabrication process of CdS film was carried out in 30mMcadmiumacetate and thioacetamide solution at 60°C temperature. The estimated thickness determined during the growth was verified by scanning electron microscopy. This study shows that in situ measurement of the thickness of thin films is feasible by this new technique, and a close match of the estimated thickness was achieved.

  • 76.
    Khartsev, Sergey I.
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    High performance latching-type luminescent magneto-optical photonic crystals2011In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, no 15, p. 2806-2808Article in journal (Refereed)
    Abstract [en]

    We report the properties of one-dimensional heteroepitaxial all-garnet magneto-optical photonic crystals (MOPCs) composed of alternating quarter-wavelength layers of diamagnetic Sm(3)Ga(5)O(12) and MO-active Bi(2.97)Er(0.03)Al(0.5)Ga(0.5)O(12) garnets rf-magnetron sputtered on Gd(3)Ga(5)O(12)(111) substrate. Substitution of ferric ions by aluminum and gallium improved transparency and induced perpendicular anisotropy in pure bismuth iron garnet. As a result, photonic crystals owned a record high magneto-optical quality and a latching-type (magnetic remnant) Faraday rotation (FR). At the resonance wavelengths 775(640)nm, a specific FR theta(F) - -14.1(14.8) deg/mu m and MO-quality factor Q = 99.3(46.2) deg represent the highest MOPC performance achieved so far.

  • 77. Kim, J. W.
    et al.
    Jelger, Pär
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sahu, J. K.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Clarkson, W. A.
    High-power and wavelength-tunable operation of an Er, Yb fiber laser using a volume Bragg grating2008In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 33, no 11, p. 1204-Article in journal (Refereed)
    Abstract [en]

    Efficient high-power operation of double-clad Er,Yb-doped fiber lasers with fixed-wavelength and wavelength-tunable resonator configurations using volume Bragg gratings for wavelength selection are reported. The fixed-wavelength laser yielded a maximum output power of 103 W at 1552.6 nm with a linewidth of ∼0.4 nm (FWHM) for a launched pump power of 290 W at 976 nm. The wavelength-tunable laser could be tuned from 1528 to 1550 nm with a linewidth of 0.2 nm (FWHM) and with output power in the range 30-38 W for a launched pump power of 120 W. The prospects for further improvement in performance are considered.

  • 78. Kores, Cristine Calil
    et al.
    Jakutis-Neto, Jonas
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pask, Helen M.
    Wetter, Niklaus U.
    Diode-side-pumped continuous wave Nd3+: YVO4 self-Raman laser at 1176 nm2015In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, no 15, p. 3524-3527Article in journal (Refereed)
    Abstract [en]

    Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd+3: YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd+3: YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

  • 79. Korn, G.
    et al.
    Thoss, A.
    Stiel, H.
    Vogt, Ulrich
    Richardson, M.
    Elsaesser, T.
    Faubel, M.
    Ultrashort 1-kHz laser plasma hard x-ray source2002In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 27, no 10, p. 866-868Article in journal (Refereed)
    Abstract [en]

    We achieved a continuous, stable, ultrashort pulse hard x-ray point source by focusing 1.8-W, 1-kHz, 50-fs laser pulses onto a novel, 30-mum-diameter, high-velocity, liquid-metal gallium jet. This target geometry avoids most of the debris problems of solid targets and provides nearly 4pi illumination. Photon fluxes of 5 X 10(8) photons/s are generated in a two-component spectrum consisting of a broad continuum from 4 to 14 keV and strong K-alpha and K-beta emission lines at 9.25 and 10.26 keV. This source will find wide use in time-resolved x-ray diffraction studies and other applications.

  • 80.
    Larsson, Jakob C.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Shaker, Kian
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Focused anti-scatter grid for background reduction in x-ray fluorescence tomography2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 11, p. 2591-2594Article in journal (Refereed)
    Abstract [en]

    X-ray fluorescence (XRF) tomography is an emerging imaging technology with the potential for high spatial resolution molecular imaging. One of the key limitations is the background noise due to Compton scattering since it degrades the signal and limits the sensitivity. In this Letter, we present a linear focused anti-scatter grid that reduces the Compton scattering background. An anti-scatter grid was manufactured and evaluated both experimentally and theoretically with Monte Carlo simulations. The measurements showed a 31% increase in signal-to-background ratio, and simulations of an improved grid showed that this can easily be extended up to > 75%. Simulated tomographies using the improved grid show a large improvement in reconstruction quality. The anti-scatter grid will be important for in vivo XRF tomography since the background reduction allows for faster scan times, lower doses, and lower nanoparticle concentrations.

  • 81.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Karlsson, H.
    Reid, D. T.
    Penman, Z.
    Ebrahimzadeh, M.
    Sibett, W.
    Broadlytunable infrared femtosecond optical parametric oscillator based onperiodically poled RbTiOAsO41997In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed)
  • 82.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Margulis, W.
    Interferometricstudy of poled glass under etching1996In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed)
  • 83.
    Levenius, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Conforti, Matteo
    Baronio, Fabio
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    De Angelis, Costantino
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Multistep quadratic cascading in broadband optical parametric generation2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 10, p. 1727-1729Article in journal (Refereed)
    Abstract [en]

    We theoretically and experimentally investigate multistep parametric processes in broadband optical parametric generators (OPGs) based on periodically poled 1 mol. % MgO-doped stoichiometric LiTaO3. We demonstrate that parametric collateral processes may deplete or enhance spectral portions of the OPG output, depending on pump pulse duration.

  • 84.
    Li, Qiang
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Song, Yi
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Zhou, Gan
    Su, Yikai
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Asymmetric plasmonic-dielectric coupler with short coupling length, high extinction ratio, and low insertion loss2010In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, no 19, p. 3153-3155Article in journal (Refereed)
    Abstract [en]

    Asymmetric directional coupling between a hybrid plasmonic waveguide with subwavelength field confinement and a conventional dielectric waveguide is investigated. The proposed hybrid coupler features short coupling length, high coupling efficiency, high extinction ratio, and low insertion loss; it can also be integrated into a silicon-based platform. This coupler can be potentially adopted for signal routing between plasmonic waveguides and dielectric waveguides in photonic integrated circuits. Furthermore, it can be exploited to efficiently excite hybrid plasmonic modes with conventional dielectric modes.

  • 85.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    A highly efficient mirrorless optical parametricoscillator pumped by nanosecond pulsesIn: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794Article in journal (Refereed)
  • 86.
    Liljestrand, Charlotte
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Highly efficient mirrorless optical parametric oscillator pumped by nanosecond pulses2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 13, p. 2435-2438Article in journal (Refereed)
    Abstract [en]

    A highly efficient mirrorless optical parametric oscillator (MOPO), pumped by narrowband nanosecond pulses at 1064 nm, is demonstrated. The MOPO is based on quasi-phase-matched parametric interaction of counter-propagating photons in 1-mm-thick periodically poled Rb-doped KTiOPO4 crystal with a period of 755 nm. It generates a co-propagating signal at 1740 nm and a counter-propagating idler at 2741 nm, achieving mJ-level output with a total signal-and-idler conversion efficiency of 47%. Both generated waves present narrow spectral bandwidths, thanks to the unique properties of the counter-propagating nonlinear interaction. The high conversion efficiency, inherently narrow spectral width, and simplicity of the optical setup make the MOPO an attractive alternative to conventional co-propagating optical parametric oscillators.

  • 87. Lindberg, H
    et al.
    Larsson, A
    Strassner, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Single-frequency operation of a high-power, long-wavelength semiconductor disk laser2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 17, p. 2260-2262Article in journal (Refereed)
    Abstract [en]

    An optically pumped, high-power, single-frequency semiconductor disk laser is demonstrated. A thin (50 mu m) diamond bonded to an InGaAsP gain chip provides the combined functions of heat removal and spectral filtering, thus eliminating the need for the additional intracavity etalons that are usually employed for single-frequency operation. In a short cavity (4 mm) configuration we obtained a maximum output power of 470 mW at 0 degrees C and 170 mW at 20 degrees C in a near-diffraction-limited beam (M-2 < 1.2). The emission wavelength was 1549 nm and the linewidth was less than 200 MHz.

  • 88. Lindberg, H.
    et al.
    Sadeghi, M.
    Westlund, M.
    Wang, S. M.
    Larsson, A.
    Strassner, M.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Mode locking a 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 20, p. 2793-2795Article in journal (Refereed)
    Abstract [en]

    Passive mode locking of an optically pumped, InP-based, 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber mirror is demonstrated. To reduce material heating and enable high-power operation, a 50 mu m thick diamond heat spreader is bonded to the surface of the gain chip. The laser operates at a repetition frequency of 2.97 GHz and emits near-transform-limited 3.2 ps pulses with an average output power of 120 mW.

  • 89. Liu, Kexin
    et al.
    Shen, Linfang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    One-way edge mode in a gyromagnetic photonic crystal slab2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 19, p. 4110-4112Article in journal (Refereed)
    Abstract [en]

    We demonstrate that one-way electromagnetic modes could be sustained by the edge of a gyromagnetic photonic crystal slab of triangular lattice under an external dc magnetic field. The applied magnetic field breaks the time-reversal symmetry of the three-dimensional system, and thus the original degeneracy point in k space, at which two dispersion surfaces intersect, is lifted, resulting in a photonic band gap below the light cone. At this band gap, the one-way mode is localized horizontally to the slab edge, while confined by the index contrast in the vertical direction.

  • 90.
    Liu, Kexin
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Torki, Amir
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    One-way surface magnetoplasmon cavity and its application for nonreciprocal devices2016In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, no 4, p. 800-803Article in journal (Refereed)
    Abstract [en]

    We theoretically analyze surface magnetoplasmon modes in a compact circular cavity made of magneto-optical material under a static magnetic field. Such a cavity provides two different methods for the surface wave to circulate in a unidirectional manner around the cavity, which offers more freedom, both in the one-way direction and in the frequency range, for designing nonreciprocal photonic components. We also show the interaction between this one-way cavity and waveguides through the example of a circulator, which lays the fundamental groundwork for potential nonreciprocal devices.

  • 91. Liu, Sheng
    et al.
    Lee, Kwang Jo
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Petropoulos, Periklis
    Richardson, David J.
    Elimination of the chirp of optical pulses through cascaded nonlinearities in periodically poled lithium niobate waveguides2010In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, no 22, p. 3724-3726Article in journal (Refereed)
    Abstract [en]

    We propose and demonstrate a novel method for the elimination of arbitrary frequency chirp from short optical pulses. The technique is based on the combination of two cascaded second-order nonlinearities in two individual periodically poled lithium niobate waveguides. The proposed scheme operates independently of the spectral phase characteristics of the input pulse, producing a near-transform-limited output.

  • 92.
    Lobov, Gleb
    et al.
    KTH, School of Engineering Sciences (SCI).
    Marinins, Aleksandrs
    KTH, School of Engineering Sciences (SCI).
    Shafagh, R. Zandi
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Zhao, Y
    KTH, School of Engineering Sciences (SCI).
    van der Wijngaart, W.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Wosinski, L.
    KTH, School of Engineering Sciences (SCI).
    Thylen, L
    KTH, School of Biotechnology (BIO).
    Toprak, M. S.
    KTH, School of Engineering Sciences (SCI).
    Haraldsson, T.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Östling, M.
    KTH, School of Information and Communication Technology (ICT).
    Popov, S.
    KTH, School of Engineering Sciences (SCI).
    Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 11, p. 2157-2160Article in journal (Refereed)
    Abstract [en]

    This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, implying a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that one-dimensional crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages, and opportunity to be tailored via adjustment of the fabrication process.

  • 93.
    Lopez-Cortes, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Tarasenko, O.
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    All-fiber Kerr cell2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 15, p. 3288-3290Article in journal (Refereed)
    Abstract [en]

    An all-fiber nanosecond Kerr light gate is described that was constructed using microstructured fibers. The switching voltage for a 20 cm long device is as low as Vp ∌ 85 V at a 1.06 Όm wavelength. The device is fully spliced. The active element is a three-hole fiber provided with internal electrodes in the side-holes and a liquid core of nitrobenzene, which is fully enclosed. This work allows the exploiting of electrically driven liquid-core fibers and demonstrated the removal of the major limitations of Kerr cells in the past, allowing for integration, safe use, and relatively low switching voltage.

  • 94.
    Lou, Fei
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Dai, Daoxin
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ultracompact polarization beam splitter based on a dielectric-hybrid plasmonic-dielectric coupler2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 16, p. 3372-3374Article in journal (Refereed)
    Abstract [en]

    An ultracompact polarization beam splitter (PBS) based on a dielectric-hybrid plasmonic-dielectric coupler is proposed. The device utilizes the polarization-dependent nature of hybrid plasmonic waveguides. By choosing proper waveguide parameters, a 2 x 5.1 mu m(2) PBS (including S-bends) with extinction ratios over 15 dB and insertion losses below 1.5 dB in the full C-band should be achievable. The effect of fabrication errors is also investigated.

  • 95. Lou, X. T.
    et al.
    Zhang, Z. G.
    Somesfalean, Gabriel
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Chen, B.
    Zhang, Y. G.
    Wang, H. S.
    Wu, S. H.
    Qin, Y. K.
    Simultaneous detection of multiple-gas species by correlation spectroscopy using a multimode diode laser2010In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, no 11, p. 1749-1751Article in journal (Refereed)
    Abstract [en]

    Simultaneous detection of multiple-gas species has for the first time (to our knowledge) been demonstrated by using a multimode diode-laser-based correlation spectroscopy (MDL-COSPEC) scheme. Concentration measurements of a mixture of CO2 and CO gas were performed by probing overlapping line spectra around 1.57 using an MDL. Species identification and corresponding quantitive analysis were implemented by correlating the recorded absorption signals of the sample gas mixtures with those of the reference gases of particular interest, attaining accuracies of 2% and 1%, respectively. MDL-COSPEC is a generic technique with potential application for simultaneous detection of multiple gases having resolvable narrow lines.

  • 96. Lu, D.
    et al.
    Peña, A.
    Segonds, P.
    Debray, J.
    Joly, S.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Yu, H.
    Zhang, H.
    Wang, J.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Boulanger, B.
    Validation of the angular quasi-phase-matching theory for the biaxial optical class using PPRKTP2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 17, p. 4276-4279Article in journal (Refereed)
    Abstract [en]

    We report the first experimental validation of angular quasi-phase-matching (AQPM) theory in a biaxial crystal by performing second-harmonic generation (SHG) in the periodically-poled Rb-doped KTiOPO4 (PPRKTP) crystal cut as a sphere. Both AQPM and birefringence phase-matching (BPM) angles were measured thanks to a Kappa circle. 

  • 97.
    Martz, Dale
    et al.
    Colorado State University.
    Alessi, D.
    Luther, B. M.
    Wang, Y.
    Kemp, D.
    Berrill, M.
    Rocca, J. J.
    High-energy 13.9 nm table-top soft-x-ray laser at 2.5 Hz repetition rate excited by a slab-pumped Ti:sapphire laser2010In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, no 10, p. 1632-1634Article in journal (Refereed)
    Abstract [en]

    We have demonstrated repetitive operation of a table-top lambda=13.9 nm Ni-like Ag soft-x-ray laser that generates laser pulses with 10 microJ energy. The soft-x-ray laser is enabled by a Ti:sapphire laser pumped by high-repetition-rate frequency-doubled high-energy Nd:glass slab amplifiers. Soft-x-ray laser operation at 2.5 Hz repetition rate resulted in 20 microwatt average power.

  • 98.
    Martz, Dale H.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Selin, Mårten
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fogelqvist, Emelie
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Holmberg, Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Legall, H.
    Blobel, G.
    Seim, C.
    Stiel, H.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    High average brightness water window source for short-exposure cryomicroscopy2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 21, p. 4425-4427Article in journal (Refereed)
    Abstract [en]

    Laboratory water window cryomicroscopy has recently demonstrated similar image quality as synchrotron-based microscopy but still with much longer exposure times, prohibiting the spread to a wider scientific community. Here we demonstrate high-resolution laboratory water window imaging of cryofrozen cells with 10 s range exposure times. The major improvement is the operation of a lambda = 2.48 nm, 2 kHz liquid nitrogen jet laser plasma source with high spatial and temporal stability at high average brightness >1.5 x 10(12) ph/(s x sr x mu m(2) x line), i.e., close to that of early synchrotrons. Thus, this source enables not only biological x-ray microscopy in the home laboratory but potentially other applications previously only accessible at synchrotron facilities.

  • 99. Mei, Liang
    et al.
    Jayaweera, Hiran
    Lundin, Patrik
    Svanberg, Sune
    Somesfalean, Gabriel
    KTH, School of Information and Communication Technology (ICT).
    Gas spectroscopy and optical path-length assessment in scattering media using a frequency-modulated continuous-wave diode laser2011In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, no 16, p. 3036-3038Article in journal (Refereed)
    Abstract [en]

    Simultaneous assessment of the spectroscopic absorption signal of gas enclosed in a scattering medium and the corresponding optical path length of the probing light is demonstrated using a single setup. Sensitive gas absorption measurements are performed by a tunable diode laser using wavelength-modulation spectroscopy, while the path length is evaluated by the frequency-modulated cw technique commonly used in the field of telecommunication. Proof-of-principle measurements are demonstrated with water vapor as the absorbing gas and using polystyrene foam as an inhomogeneously scattering medium. The combination of these techniques opens up new possibilities for straightforward evaluation of gas presence and exchange in scattering media.

  • 100. Meng, Lijun
    et al.
    Zhao, Ding
    Ruan, Zhichao
    Li, Qiang
    Yang, Yuanqing
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Optimized grating as an ultra-narrow band absorber or plasmonic sensor2014In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 5, p. 1137-1140Article in journal (Refereed)
    Abstract [en]

    Lamellar gratings are investigated via temporal coupled-mode theory and numerical simulations. Total absorption can be achieved by an optimized grating with shallow grooves under normal incidence and the full width at half-maximum (FWHM) is only 0.4 nm. For certain wavelengths, the structure shows high absorption only within an ultra-narrow angle, which suggests that it can be used as a highly directional thermal emitter according to Kirchhoff's law. Besides, the resonant wavelength is sensitive to the refractive index of the environmental dielectric. The large sensitivity (1400 nm/RIU) and simultaneous small FWHM result in a huge figure-of-merit of 2300/RIU, which enables the structure to have great potential in plasmonic sensing.

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