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  • 1351.
    Yan, Wei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Generalized nihility media from transformation optics2011Ingår i: Journal of optics, ISSN 0150-536X, Vol. 13, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nihility media in the previous literature are usually understood as media with epsilon = mu = 0. Transformation optics opens a new perspective for capturing the essence of such media. From this perspective, we generalize the definition of nihility media as transformation media derived from volumeless geometrical elements. A volumeless geometrical elements can be either a point (P), a line (L), or a surface (S). Their corresponding transformation media are therefore called P-, L-, or S-type nihility media, respectively. The previous defined nihility media with epsilon = mu = 0 is a special case under the P-type nihility media. The constructions of nihility media by metamaterials are discussed. The eigenfields in different types of nihility media are derived. The interactions between an externally incident wave and a slab of nihility media in a free space background are analyzed. Furthermore, we discuss compensated bilayers composed of nihility media. It is shown that for a slab of P-type nihility media, a normally incident wave can perfectly transmit through, while all obliquely incident waves are completely blocked; for a slab made of L-type nihility media, both normally and obliquely incident waves can transmit with some reflections, which can be eliminated by adding a compensating L-type nihility media; for a slab of S-type nihility media, all field components can perfectly transmit through.

  • 1352.
    Yan, Wei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Manipulation of light with alpha transformation media2011Ingår i: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, ISSN 1084-7529, Vol. 28, nr 6, s. 1058-1066Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A type of transformation media called a media is proposed by performing a direct transformation to the metric tensor of another kind of media, called seed media. Light rays in an alpha medium correlate to those in its seed medium through a simple displacement or rotation relation. Three types of commonly encountered anisotropic media are covered by the concept of alpha media: (1) media of slab shape, having continuous translational symmetry with respect to two Cartesian coordinate components; (2) media of cylindrical shape, having cylindrical rotational symmetry and continuous translational symmetry along the longitudinal direction; (3) media of spherical shape, having spherical rotational symmetry, with two principal axes along the symmetry directions, and with the material parameters in the same sign. Optical properties of such media can be effectively interpreted through recalling the properties of certain isotropic media, i.e., their seed media. Conversely, from simple isotropic media in which light trajectories are well known, one can design a media for manipulating light. Based on this fact, several optical devices, including frequency demultiplexers, beam splitters, focusing lenses, and radiation controllers, are designed and numerically verified. The famed invisibility cloak derived from a conventional coordinate transformation is revisited from the alpha media perspective.

  • 1353.
    Yan, Wei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Manipulation of light with α transformation media2011Ingår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 28, nr 6, s. 1058-1066Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A type of transformation media called α media is proposed by performing a direct transformation to the metric tensor of another kind of media, called seed media. Light rays in an α medium correlate to those in its seed medium through a simple displacement or rotation relation. Three types of commonly encountered anisotropic media are covered by the concept of α media: (1) media of slab shape, having continuous translational symmetry with respect to two Cartesian coordinate components; (2) media of cylindrical shape, having cylindrical rotational symmetry and continuous translational symmetry along the longitudinal direction; (3) media of spherical shape, having spherical rotational symmetry, with two principal axes along the symmetry directions, and with the material parameters in the same sign. Optical properties of such media can be effectively interpreted through recalling the properties of certain isotropic media, i.e., their seed media. Conversely, from simple isotropic media in which light trajectories are well known, one can design α media for manipulating light. Based on this fact, several optical devices, including frequency demultiplexers, beam splitters, focusing lenses, and radiation controllers, are designed and numerically verified. The famed invisibility cloak derived from a conventional coordinate transformation is revisited from the α media perspective.

  • 1354.
    Yan, Wei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Non-magnetic simplified cylindrical cloak with suppressed zeroth order scattering2008Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A type of simplified cloaks with matched exterior boundaries is proposed. The cloak uses nonmagnetic material for the TM polarization and can function with a relatively thin thickness. It is shown that the zeroth order scattering of such cloak is dominant among all cylindrical scattering terms. A gap is added at the cloak's inner surface to eliminate the zeroth order scattering through the mechanism of scattering resonance. The reduction in scattering is relatively smooth, indicating that the proposed scattering reduction method has good tolerance to perturbations. Numerical simulations also confirm that the proposed structure has very low scattering.

  • 1355. Yang, Jia-Xiang
    et al.
    Li, Lin
    Wang, Cai-Xia
    Tian, Yu-Peng
    Wu, Fei
    Xing, Xiao-Juan
    Wang, Chuan-Kui
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Tang, Huo-Hong
    Huang, Wen-Hao
    Tao, Xu-Tang
    Jiang, Min-Hua
    Facile synthesis, optical properties and theoretical calculation of two novel two-photon absorption chromophores2010Ingår i: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 130, nr 4, s. 654-659Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two heterocycle-based derivatives that can be used as two-photon absorption chromophore, 9-butyl-3-(2,6-diphenylpyridin-4-yl)-9H-carbazole (BDPYC) and 9-butyl-3-(4-(2, 6-diphenylpyridin-4-yl)styryl)-9H-carbazole (BDPSC) have been successfully synthesized and fully characterized by elemental analysis, IR, H-1 NMR, C-13 NMR and MS. The molecules possess D-pi-A structures, but have different pi bridge. The 9-butylcarbazole is used as a donor (D), and the pyridine ring is used as an acceptor (A). One- and two-photon absorption and excited fluorescence properties in various solvents were experimentally investigated. Two-photon initiated optical data recording experiments have been carried Out under 740 nm laser radiation, and the possible mechanism of optical data storage is discussed based on theoretical calculations.

  • 1356. Yang, L.
    et al.
    Somesfalean, G.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Laser absorption spectroscopy of oxygen confined in highly porous hollow sphere xerogel2014Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 3, s. 2584-2594Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An Al2O3 xerogel with a distinctive microstructure is studied for the application of laser absorption spectroscopy of oxygen. The xerogel has an exceptionally high porosity (up to 88%) and a large pore size (up to 3.6μm). Using the method of gas-in-scattering media absorption spectroscopy (GASMAS), a long optical path length (about 3.5m) and high enhancement factor (over 300 times) are achieved as the result of extremely strong multiple-scattering when the light is transmitted through the airfilled, hollow-sphere alumina xerogel. We investigate how the microphysical feature influences the optical property. As part of the optical sensing system, the material's gas exchange dynamics are also experimentally studied.

  • 1357. Yang, Liu
    et al.
    Kou, Pengfei
    Shen, Jianqi
    Lee, El Hang
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang University, China.
    Proposal of a broadband, polarization-insensitive and high-efficiency hot-carrier schottky photodetector integrated with a plasmonic silicon ridge waveguide2015Ingår i: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 17, nr 12, artikel-id 125010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a broadband, polarization-insensitive and high-efficiency plasmonic Schottky diode for detection of sub-bandgap photons in the optical communication wavelength range through internal photoemission (IPE). The distinctive features of this design are that it has a gold film covering both the top and the sidewalls of a dielectric silicon ridge waveguide with the Schottky contact formed at the gold-silicon interface and the sidewall coverage of gold can be easily tuned by an insulating layer. An extensive physical model on IPE of hot carriers is presented in detail and is applied to calculate and examine the performance of this detector. In comparison with a diode having only the top gold contact, the polarization sensitivity of the responsivity is greatly minimized in our photodetector with gold film covering both the top and the sidewall. Much higher responsivities for both polarizations are also achieved over a broad wavelength range of 1.2-1.6 mu m. Moreover, the Schottky contact is only 4 mu m long, leading to a very small dark current. Our design is very promising for practical applications in high-density silicon photonic integration.

  • 1358. Yang, Liu
    et al.
    Mo, Lei
    Chen, Tuo
    Forsberg, Erik
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang Univ.
    A checkerboard selective absorber with excellent spectral selectivity2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, nr 18, artikel-id 183103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A selective absorber with excellent spectral selectivity is proposed and analyzed. The absorber is based on a germanium (Ge) checkerboard on top of a tantalum (Ta) substrate. At wavelengths shorter than the 1.2 mu m cutoff, a very high absorption is achieved due to strong cavity resonances in the Ge nanosquares, and their interactions with adjacent nanocavities and the bottom Ta substrate. At longer wavelengths, absorption is greatly suppressed due to destructive interference between the transparent checkerboard layer and the highly reflective Ta substrate. To better describe the superior selectivity of our configuration, a new figure of merit (FOM) is introduced. We observe a FOM value of 0.88 compared to 0.69 for its planar counterpart. We also conduct a thermal analysis to verify the excellent selectivity of our absorber. A high temperature can be achieved and maintained, promising good potential for applications in solar thermophotovoltaic systems.

  • 1359.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Larsson, Jim
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Xu, Can
    Brydegaard, Mikkel
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Atmospheric CO2-detection via Scheimpflug DIAL Employing a Simple Fiber Amplifier2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ever-increasing worldwide environmental awareness has prompted much effort to minimize humanity’s ecological footprint. This has led to increased demands for reliable technologies for assessing the current situation as well as the efficiency of new policies and interventions. In particular, CO2-monitoring has attracted lots of attention as CO2 is the greenhouse gas that is emitted in the largest quantities.

  • 1360.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. 2Centre for Optical and Electromagnetic Research (COER), State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, 310058 Hangzhou, China.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    A 1.57 μm fiber source for CO2 Scheimpflug DIAL2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    A 1.3 W, narrow linewidth source at 1.57 μm for Scheimpflug DIAL was developed. Itwas tunable from 1570.859 nm to 1573.068 nm with a 2.9 MHz linewidth, and used for CO2measurements.

  • 1361.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Larsson, Jim
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden..
    Bood, Joakim
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden..
    Brydegaard, Mikkel
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden.;Norsk Elektro Optikk AS, Prost Stabels Vei 22, N-2019 Skedsmokorset, Norway..
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    1.57 mu m fiber source for atmospheric CO2 continuous-wave differential absorption lidar2019Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, nr 7, s. 10304-10310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an efficient fiber source designed for continuous-wave differential absorption light detection and ranging (CW DIAL) of atmospheric CO2-concentration. It has a linewidth of 3 MHz, a tuning range of 2 nm over the CO2 absorption peaks at 1.572 mu m, and an output power of 1.3 W limited by available pump power. Results from the initial CW DIAL testing are also presented and discussed. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 1362.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Larsson, Jim
    Xu, Can
    Brydegaard, Mikkel
    Bood, Joakim
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
    A 1.57 µm fiber source for atmospheric CO2 continuous-wave differential absorption lidar2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a simple turn-key fiber amplifier system which allows for a narrow wavelength tunability with a stable level of output power.  This system was used in continuous-wave differential absorption light detection and ranging (CW-DIAL) [1] to measure the atmospheric CO2-concentration in Lund. Preliminary experimental results are also presented.

  • 1363.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Centre for Optical and Electromagnetic Research (COER), State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, 310058, China.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Magrulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Department of Fiber Optics, RISE Acreo, Kista, 164 40, Sweden.
    Fröjdh, Krister
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Continuously tunable, narrow-linewidth laser based on a semiconductor optical amplifier and a linearly chirped fiber Bragg grating2019Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, nr 10, s. 14213-14220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe a simple, narrow-linewidth, tunable fiber-based laser with a high degree of tuning accuracy. A polarization independent semiconductor optical amplifier (SOA) is used as the gain medium in a unidirectional fiber ring cavity with a circulator connected to a 6-meter long chirped fiber Bragg grating (CFBG). The laser wavelength is chosen by setting the modulation frequency of the SOA the same as the harmonics of the fundamental repetition rate of the light reflected at a specific point on the CFBG. Careful management of the drive current and pulse width helps to generate laser light of narrow linewidth (less than 0.03 nm) with low power variation (1.46 dB) over a tuning range of 40 nm.

  • 1364. Yavas, Ozlem
    et al.
    Svedendahl, Mikael
    Barcelona Institute of Science and Technology, Spain.
    Dobosz, Paulina
    Sanz, Vanesa
    Quidant, Romain
    On-a-chip Biosensing Based on All-Dielectric Nanoresonators2017Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, nr 7, s. 4421-4426Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanophotonics has become a key enabling technology in biomedicine with great promises in early diagnosis and less invasive therapies. In this context, the unique capability of plasmonic noble metal nanoparticles to concentrate light on the nanometer scale has widely contributed to biosensing and enhanced spectroscopy. Recently, high-refractive index dielectric nanostructures featuring low loss resonances have been proposed as a promising alternative to nanoplasmonics, potentially offering better sensing performances along with full compatibility with the microelectronics industry. In this letter we report the fitst demonstration of biosensing with silicon nanoresonators integrated in state-of-the-art microfluidics. Our lab-on-a-chip platform enables detecting Prostate Specific Antigen (PSA) cancer marker in human serum with a sensitivity that meefs clinical needs. These performances are directly compared with its plasmonic counterpart based on gold nanorods. Our work opens new opportunities in the development of future point-of-care devices toward a more personalized healthcare.

  • 1365. Ye, T.
    et al.
    Lu, Y.
    Liu, F.
    Li, Q.
    Zhang, Ziyang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Su, Y.
    160-Gb/s NRZ-to-PSK conversion using linear filtering in silicon ring resonators2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a scheme to achieve high-speed, all-optical non-retum-to-zero to phase-shift keying (NRZ-to-PSK) conversion by using the linear filtering in the silicon ring resonators. Simulation results are provided to verify the feasibility.

  • 1366. Yong, Y. -S
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S. A.
    Carvajal, J. J.
    Díaz, F.
    Herek, J. L.
    García-Blanco, S. M.
    Pollnau, Markus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik. University of Twente, Netherlands.
    Direct confocal lifetime measurements on rare-earth-doped media exhibiting radiation trapping2017Ingår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, nr 2, s. 527-532Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Radiation trapping occurs in rare-earth-doped active media with strong spectral overlap of luminescence and ground-state absorption. It is demonstrated experimentally that a confocal measurement mitigates the influence of radiation trapping on the measured luminescence lifetime, hence allowing for direct extraction of the lifetime from the measured decay curves. The radiation trapping effect is largely suppressed by probing a small sample volume and rejecting the photons reemitted from the unpumped region. This non-destructive measurement method is applied to ytterbium (Yb3+) activated potassium double tungstate crystalline layers with Yb3+ concentrations ranging from 1.2 at.% up to 76 at.% (~8 × 1019 - 5 × 1021 cm-3). The measured lifetime values are comparable to the results reported for Yb3+-doped potassium double tungstate powder diluted in liquid.

  • 1367. Yong, Yean-Sheng
    et al.
    Aravazhi, Shanmugam
    Vazquez-Cordova, Sergio A.
    Carjaval, Joan J.
    Diaz, Francesc
    Herek, Jennifer L.
    Garcia-Blanco, Sonia M.
    Pollnau, Markus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Temperature-dependent absorption and emission of potassium double tungstates with high ytterbium content2016Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 23, s. 26825-26837Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the spectroscopic properties of thin films of potassium ytterbium gadolinium double tungstates, KYb0.57Gd0.43(WO4)(2), and potassium ytterbium lutetium double tungstates, KYb0.76Lu0.24(WO4)(2), specifically at the central absorption line near 981 nm wavelength, which is important for amplifiers and lasers. The absorption cross-section of both thin films is found to be similar to those of bulk potassium rare-earth double tungstates, suggesting that the crystalline layers retain their spectroscopic properties albeit having >50 at.% Yb3+ concentration. The influence of sample temperature is investigated and found to substantially affect the measured absorption cross-section. Since amplifiers and lasers typically operate above room temperature due to pump-induced heating, the temperature dependence of the peak-absorption cross-section of the KYb0.57Gd0.43(WO4)(2) is evaluated for the sample being heated from 20 degrees C to 170 degrees C, resulting in a measured reduction of peak-absorption cross-section at the transitions near 933 nm and 981 nm by similar to 40% and similar to 52%, respectively. It is shown that two effects, the change of Stark-level population and linewidth broadening due to intra-manifold relaxation induced by temperature-dependent electronphonon interaction, contribute to the observed behavior. The effective emission cross-sections versus temperature have been calculated. Luminescence-decay measurements show no significant dependence of the luminescence lifetime on temperature.

  • 1368. Yong, Y.S.
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S.A.
    García-Blanco, S.M.
    Pollnau, Markus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik. Integrated Optical MicroSystems Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, Enschede, Netherlands.
    Highly Yb-doped KGd(WO4)2 thin-film amplifier2015Ingår i: CLEO: Science and Innovations 2015, Optical Society of America, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report record-high small-signal gain of 1050 dB/cm at 981 nm wavelength in a KGd<inf>0.425</inf>Yb<inf>0.575</inf>(WO<inf>4</inf>)<inf>2</inf> thin film. The sensitivity of gain to the shift of beam-focus position, which is critical under non-waveguiding conditions, is investigated.

  • 1369. Yu, Huakang
    et al.
    Fang, Wei
    Gu, Fuxing
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yang, Zongyin
    Tong, Limin
    Longitudinal Lorentz force on a subwavelength-diameter optical fiber2011Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 83, nr 5, s. 053830-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyze the longitudinal Lorentz forces that a propagating continuous-wave light exerts on a subwavelength-diameter optical fiber. Our theoretical results show that, during the propagating process, the guided light exerts no net time-averaged force on the fiber. Via numerical simulation, we find a significant overall pull force of 0.4 pN/mW acting on a 450-nm-diam fiber tip at a wavelength of 980 nm due to the scattering of the end face and a calculated force distribution reveals the feature of a near-field accumulation. Our results may be helpful to the configuration of optomechanical components or devices based on these fibers.

  • 1370. Yu, Longhai
    et al.
    Yin, Yanlong
    Shi, Yaocheng
    Dai, Daoxin
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang University, China.
    Thermally tunable silicon photonic microdisk resonator with transparent graphene nanoheaters2016Ingår i: Operator Theory: Advances and Applications, ISSN 1004-4469, E-ISSN 2334-2536, Vol. 3, nr 2, s. 159-166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient tunable photonic integrated devices are important for the realization of reconfigurable photonic systems. Thermal tuning is a convenient and effective approach, and silicon's large heat conductivity, thermo-optical coefficient, and CMOS fabrication compatibility make it a good candidate material for tunable optical microcavities, which are versatile elements in low-cost, large-scale photonic integrated circuits. Metal heaters are traditionally used for tuning, and a thick SiO2 upper-cladding layer is usually needed to prevent light absorption by the metal since that could reduce response speed and heating efficiency. In this paper, we propose and experimentally demonstrate thermally tunable silicon photonic microdisk resonators by introducing transparent graphene nanoheaters, which contact the silicon core directly without any isolator layer. The theoretical and experimental results show that the transparent graphene nanoheaters improve the heating efficiency, the temporal response, and the achievable temperature in comparison with a traditional metal heater. Furthermore, the graphene nanoheater is convenient for use in ultrasmall nanophotonic integrated devices due to its single-atom thickness and excellent flexibility. Both experiments and simulations show that the transparent graphene nanoheater is a promising option for other thermally tunable photonic integrated devices such as optical filters and switches.

  • 1371.
    Yu, Longhai
    et al.
    Zhejiang Univ. (China).
    Zheng, Jiajiu
    Zhejiang Univ. (China).
    Dai, Daoxin
    Zhejiang Univ. (China).
    He, Sailing
    Zhejiang Univ. (China).
    Observation of optically induced transparency effect in silicon nanophotonic wires with graphene2014Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Graphene, a well-known two-dimensional sheet of carbon atoms in a honeycomb structure, has many unique and fascinating properties in optoelectronics and photonics. Integration of graphene on silicon nanophotonic wires is a promising approach to enhance light-graphene interactions. In this paper, we demonstrate on-chip silicon nanophotonic wires covered by graphene with CMOS-compatible fabrication processes. Under the illumination of pump light on the graphene sheet, a loss reduction of silicon nanophotonic wires, which is called optically induced transparency (OIT) effect, is observed over a broad wavelength range for the first time. The pump power required to generate the OIT effect is as low as ~0.1mW and the corresponding power density is about 2×10 3mW/cm2, which is significantly different from the saturated absorption effect of graphene reported previously. The extremely low power density implies a new mechanism for the present OIT effect, which will be beneficial to realize silicon on-chip all-optical controlling in the future. It also suggests a new and efficient approach to tune the carrier concentration (doping level) in graphene optically.

  • 1372.
    Yu, Shun
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Zuleta, Marcelo
    Tian, Haining
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Weissenrieder, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Yang, Xichuan
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO2(110)2010Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, nr 22, s. 224704-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fast development of new organic sensitizers leads to the need for a better understanding of the complexity and significance of their adsorption processes on TiO2 surfaces. We have investigated a prototype of the triphenylamine-cyanoacrylic acid (donor-acceptor) on rutile TiO2 (110) surface with special attention on the monolayer region. This molecule belongs to the type of dye, some of which so far has delivered the record efficiency of 10%-10.3% for pure organic sensitizers [W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang, C. Pan, and P. Wang, Chem. Mater. 22, 1915 (2010)]. The molecular configuration of this dye on the TiO2 surface was found to vary with coverage and adopt gradually an upright geometry, as determined from near edge x-ray absorption fine structure spectroscopy. Due to the molecular interaction within the increasingly dense packed layer, the molecular electronic structure changes systematically: all energy levels shift to higher binding energies, as shown by photoelectron spectroscopy. Furthermore, the investigation of charge delocalization within the molecule was carried out by means of resonant photoelectron spectroscopy. A fast delocalization (similar to 1.8 fs) occurs at the donor part while a competing process between delocalization and localization takes place at the acceptor part. This depicts the "push-pull" concept in donor-acceptor molecular system in time scale. (C) 2010 American Institute of Physics. [doi:10.1063/1.3509389]

  • 1373. Yu, Xia
    et al.
    Liu, Min
    Chung, Youngjoo
    Yan, Min
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Coupling coefficient of two-core microstructured optical fiber2006Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 260, nr 1, s. 164-169Artikel i tidskrift (Refereegranskat)
  • 1374. Yu, Xia
    et al.
    Yan, Min
    Nanyang Techbological University, Singapore.
    Luo, Lian Wee
    Shum, Ping
    Theoretical investigation of highly birefringent all-solid photonic bandgap fiber with elliptical cladding rods2006Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, nr 11, s. 1243-1245Artikel i tidskrift (Refereegranskat)
  • 1375.
    Yu, Xia
    et al.
    Singapore Institute of Manufacturing Technology, Singapore.
    Yan, Min
    Technical University of Denmark.
    Ren, Guobin
    Tong, Weijun
    Cheng, Xueping
    Zhou, Junqiang
    Shum, Perry Ping
    Ngo, Nam Quoc
    Nanostructure core fiber with enhanced performances: Design, fabrication and devices2009Ingår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 27, nr 11, s. 1548-1555Artikel i tidskrift (Refereegranskat)
  • 1376. Yu, Xianbin
    et al.
    Jia, Shi
    Pang, Xiaodan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Morioka, Toshio
    Oxenloewe, Leif K.
    Beyond 100 Gbit/s wireless connectivity enabled by THz photonics2017Ingår i: Transparent Optical Networks (ICTON), 2017 19th International Conference on, IEEE Computer Society, 2017, s. 1-4Konferensbidrag (Refereegranskat)
    Abstract [en]

    Beyond 100Gbit/s wireless connectivity is appreciated in many scenarios, such as big data wireless cloud, ultrafast wireless download, large volume data transfer, etc. In this paper, we will present our recent achievements on beyond 100Gbit/s ultrafast terahertz (THz) wireless links enabled by THz photonics.

  • 1377. Yu, Xianbin
    et al.
    Zhao, Ying
    Deng, Lei
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Tafur Monroy, Idelfonso
    Existing PON Infrastructure Supported Hybrid Fiber-Wireless Sensor Networks2012Ingår i: National Fiber Optic Engineers Conference, NFOEC 2012, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose a hybrid fiber wireless sensor network based on the existing PON infrastructure. The feasibility of remote sensing and PON convergence is experimentally proven by transmitting direct-sequence spread-spectrum wireless sensing and 2.5Gbps GPON signals.

  • 1378.
    Yu, Yichuan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Karlsson, Stefan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Liu, C. P.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Chuang, C. H.
    He, Sailing
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Seeds, A. J.
    Krysa, A. B.
    Roberts, J. S.
    Intermodulation Distortion Suppression in a Full-Duplex Radio-over-Fibre System Employing Asymmetric Fabry-Perot Modulator/Detector2006Ingår i: 2006 European Conference on Optical Communications Proceedings, ECOC 2006, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The property of intermodulation distortion in a full-duplex radio-over-fibre system with Asymmetric Fabry-Perot Modulator/Detector was investigated. By employing the balanced RF input powers, intermodulation distortion was suppressed and a SFDR of 99dB. Hz2/3 has been achieved.

  • 1379.
    Yu, Zhangwei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Knape, Harald
    Tarasenko, Olesandr
    Koch, Ralf
    Margulis, Walter
    All-fiber single-pulse selection and nanosecond gating2009Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, nr 7, s. 1024-1026Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two functions normally attributed to Pockels cells are performed with internal-electrode microstructured fiber components. Single-pulse selection out of a 100 MHz mode-locked pulse train is demonstrated using all-fiber nanosecond polarization rotation. Additionally, off-on-off gating with duration similar to 13 ns is achieved with a polarization rotator made out of a four-hole silicate fiber.

  • 1380.
    Yu, Zhangwei
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Malmström, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Sterner, C.
    Tarasenko, O.
    Margulis, Walther
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Fonjallaz, P. -Y
    Dynamics of long-period gratings tuned with internal fiber electrodes2011Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, nr 5, s. 633-635Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The physics of electrically switched long-period grating in a twin-hole fiber with internal electrodes is studied. Dynamic measurements for the two polarizations show how the grating spectra shift in time due to the mechanical stress and heat transfer in the core and the cladding.

  • 1381.
    Yu, Zhangwei
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Malmström, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Tarasenko, O.
    Margulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Actively Q-switched all-fiber laser with an electrically controlled microstructured fiber2010Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, nr 11, s. 11052-11057Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actively Q-switching of an all-fiber laser system is demonstrated. The active element is a polarization switch with nanosecond risetime based on a microstructured fiber with electrically driven internal electrodes. Optical feedback between two 100% reflectors is inhibited until a nanosecond current pulse Q-switches the laser. After a short optical pulse develops several roundtrips later, the fiber switch is turned off, removing the short optical pulse from the cavity through a polarization splitter. Pulses of 50 W peak power and similar to 12 ns duration are obtained with 400 mW pump power at 100 Hz. (C) 2010 Optical Society of America

  • 1382.
    Yu, Zhangwei
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Margulis, Walter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Fonjallaz, Pierre-Yves
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Tarasenko, Oleksandr V.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Physics of electricity switched fiber Bragg gratings2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    The physics of electrically switched FBGs was studied in fibers with internal electrodes. Wavelength shifts due to mechanical effects (nanoseconds) and heat (milliseconds) depend quadratically on the electrical pulse voltage and linearly on pulse duration.

  • 1383.
    Yu, Zhangwei
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Acreo AB, Kista, Sweden .
    Margulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Acreo AB, Kista, Sweden .
    Malmström, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Acreo AB, Kista, Sweden .
    Tarasenko, O.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Acreo AB, Kista, Sweden .
    Q-switching a fiber laser with an electrically controlled microstructured fiber2010Ingår i: Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010, 2010, s. 5500945-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A monolithic fiber laser incorporating an electrically driven microstructured fiber is Q-switched exploiting nanosecond polarization rotation and multi-pass amplification. All components are in-fiber, simplifying fabrication and improving robustness.

  • 1384.
    Yu, Zhangwei
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Margulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Tarasenko, O.
    Malmström, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    All-fiber laser cavity dumping2009Ingår i: 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS, IEEE , 2009, s. 463-464Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cavity dumping of a fiber laser is demonstrated. A microstructured fiber with an electrically driven internal electrode is used for intracavity polarization rotation with nanosecond risetime. The optical flux can be dumped within one roundtrip.

  • 1385.
    Yu, Zhenhua
    et al.
    Niels Bohr Inst, Copenhagen O, Denmark ; Ohio State Univ, Columbus, OH USA ; Tsinghua Univ, Beijing, Peoples R China .
    Pethick, Christopher J.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Induced interactions in dilute atomic gases and liquid helium mixtures2012Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 85, nr 6, s. 063616-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In dilute mixtures of two atomic gases, interactions between two minority atoms acquire a contribution due to interaction with the majority component. Using thermodynamic arguments, we derive expressions for this induced interaction for both fermions and bosons for arbitrary strength of the interaction between the two components. Implications of the work for the theory of dilute solutions of He-3 in liquid He-4 are discussed.

  • 1386. Yurkin, Yu.T.
    et al.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Wu, Yueshi
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Zverev, V. G.
    et al.,
    Trapped antiprotons in the Earth inner radiation belt in PAMELA experiment2011Ingår i: Bulletin of the Russian Academy of Sciences: Physics, ISSN 1062-8738, Vol. 75, nr 6, s. 854-856Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The existence of trapped antiprotons in the Earth's inner radiation belt has been theoretically predicted, but not observed. We present a procedure for antiproton selection and the observation results from the PAMELA space experiment measurements. The PAMELA magnetic spectrometer ensures reliable identification of particles and charge signs, value determination, and energy measurement, thus enabling us to experimentally establish the existence of antiprotons trapped in the Earth's inner radiation belt.

  • 1387.
    Zafra, Sebastian Ortega
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO. Acreo Swedish ICT AB, Sweden.
    Pang, Xiaodan
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Sergeyev, Sergey
    Phase noise tolerance study in coherent optical circular QAM transmissions with Viterbi-Viterbi carrier phase estimation2014Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 25, s. 30579-30585Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a performance evaluation of a non-conventional approach to implement phase noise tolerant optical systems with multilevel modulation formats. The performance of normalized Viterbi-Viterbi carrier phase estimation (V-V CPE) is investigated in detail for circular m-level quadrature amplitude modulation (C-mQAM) signals. The intrinsic property of C-mQAM constellation points with a uniform phase separation allows a straightforward employment of V-V CPE without the need to adapt constellation. Compared with conventional feed-forward CPE for square QAM signals, the simulated results show an enhanced tolerance of linewidth symbol duration product (Delta vT(s)) at a low sensitivity penalty by using feed-forward CPE structure with C-mQAM. This scheme can be easily upgraded to higher order modulations without inducing considerable complexity.

  • 1388.
    Zakomirnyi, Vadim
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Siberian Federal University, Krasnoyarsk, Russian Federation.
    Rasskazov, I. L.
    Gerasimov, V. S.
    Ershov, A. E.
    Polyutov, S. P.
    Karpov, S. V.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Siberian Federal University, Krasnoyarsk, Russian Federation.
    Titanium nitride nanoparticles as an alternative platform for plasmonic waveguides in the visible and telecommunication wavelength ranges2018Ingår i: Photonics and Nanostructures - Fundamentals and Applications, ISSN 1569-4410, Vol. 30, s. 50-56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose to utilize titanium nitride (TiN) as an alternative material for linear periodic chains (LPCs) of nanoparticles (NPs) which support surface plasmon polariton (SPP) propagation. Dispersion and transmission properties of LPCs have been examined within the framework of the dipole approximation for NPs with various shapes: spheres, prolate and oblate spheroids. It is shown that LPCs of TiN NPs support high-Q eigenmodes for an SPP attenuation that is comparable with LPCs from conventional plasmonic materials such as Au or Ag, with the advantage that the refractory properties and cheap fabrication of TiN nanostructures are more preferable in practical implementations compared to Au and Ag. We show that the SPP decay in TiN LPCs remains almost the same even at extremely high temperatures which is impossible to reach with conventional plasmonic materials. Finally, we show that the bandwidth of TiN LPCs from non-spherical particles can be tuned from the visible to the telecommunication wavelength range by switching the SPP polarization, which is an attractive feature for integrating these structures into modern photonic devices.

  • 1389.
    Zeil, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Tailored fiber lasers and their use in nonlinear optics2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The objective of this thesis work was to develop tailored fiber lasers, which meet the pump requirement for efficient continuous-wave (cw) frequency conversion to the visible and the mid-infrared wavelength regimes: a stable, high-power, wavelength-tunable, narrow-linewidth output in a single polarization. As a first step, the prospect of tuning ytterbium fiber lasers over an unprecedented wavelength range, from 980nm to 1100nm, was investigated. The results further substantiate the enormous potential of fiber lasers to act as widely tunable pump sources for nonlinear frequency conversion schemes, allowing the design of coherent light sources in large parts of the optical spectrum. Subsequently, a method of flexible wavelength-tuning and -locking for high-power fiber oscillators was demonstrated, incorporating the use of a highly reflective transversely-chirped volume Bragg grating as cavity mirror. Through a simple lateral translation of the grating, continuous wavelength-tuning over 2.5 THz was achieved without sacrificing efficiency, spectral or spatial beam quality. As the latter free-space laser architecture relied on an intra-cavity polarization filter to ensure a linearly polarized output state, the filtered orthogonal polarization state was available for a secondary laser oscillation. Following this basic design idea, a high-power dual-wavelength laser with a tunable wavelength separation of up to 2 THz was demonstrated. With both signals separated in wavelength and polarization, gain competition was effectively suppressed and the presented source possessed the necessary stability for potential use in power-demanding applications such as difference frequency generation of cw THz radiation. After establishing a flexible and reliable fiber pump source, continuous-wave, quasi-phase matched, second harmonic generation experiments were performed on several crystals from the KTiOPO4 family. The power scaling limitations of these materials, when generating high-power signals in the visible spectral range were studied. Although, a conclusive identication of the optimal KTiOPO4 isomorph for this process was hindered due to varying crystal quality from different vendors, comparative transmission studies suggest that the arsenate isomorph, KTiOAsO4, could be best suited by virtue of its low linear absorption in the visible region. Finally, a singly-resonant optical parametric oscillator, pumped by the above narrowband fiber laser source, efficiently generated 11W of mid-infrared radiation at 3.4 µm and 19W single-frequency radiation at 1.55 µm. Stable, high-power operation of this parametric source was facilitated by a novel method of controlling the intra-cavity signal power using a volume Bragg grating with variable reectivity.

  • 1390.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Volume Bragg grating controlled fiber lasers2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In recent years, rare earth doped fiber lasers have experienced remarkable progress in terms of power scaling, warranting their use in numerous research and industry applications. Especially, the rapid rise in output powers an be attributed to the fact that the fiber laser design naturally promotes good thermal handling capabilities, over-all efficiency and exceptional spatial beam qualities. Moreover, the broad fluorescence spectra of the used rare earth gain media allow great flexibility in operating wavelength. However, proper restriction and stabilization of the spectral properties has to keep up with the rapid increase in power levels, without sacrificing the advantages of fiber lasers. In our work, we demonstrate how the implementation of volume-Bragg grating can cater for that demand. We show how this generic technology can be applied to increase the spectral brightness and to permit flexible wavelength-tuning and discuss its advantages and limitations with respect to other approaches.

  • 1391.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Efficient spectral control and tuning of a high-power narrow-linewidth Yb-doped fiber laser using a transversally chirped volume-Bragg grating (TCVBG)2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we present a high-power (>100 W) tunable Yb-berlaser oscillator. Facile tuning over 2.5 THz of the narrow-band (10GHz) signal was achieved by translating a transversally chirpedvolume-Bragg grating whilst maintaining constant output powerand the polarization.

  • 1392.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Tunable, high-power, continuous-wave dual-polarization Yb-fiber oscillator2015Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, nr 13, s. 17450-17455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a high-power, dual-polarization Yb-fiber oscillator, by separately locking the two linear polarization states defined by slow and fast axis of a polarization-maintaining gain fiber with volume Bragg gratings. Dual-line lasing is achieved with a tunable wavelength separation from 0.03 to 2 THz, while exceeding output powers of 78 W over the entire tuning range, maintaining a high beam-quality with M-2<1.2. With this laser configuration we achieve a peak-to-peak power variation of <1% for the dual-line signal and <3% for the individual signals.

  • 1393.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Eciency-optimized, 30W continuous-waveOPO employing a variable re ectivity volume Bragg grating2015Konferensbidrag (Refereegranskat)
  • 1394.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    High-power, single-frequency, continuous-waveoptical parametric oscillator employing avariable reflectivity volume Bragg grating2014Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 24, s. 29907-29913Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A continuous-wave singly-resonant optical parametric oscillator (SRO) with an optimum extraction efficiency, that can be adjusted independent of the pump power, is demonstrated. The scheme employs a variable-reflectivity volume Bragg grating (VBG) as the output coupler of a ring cavity, omitting any additional intra-cavity elements. In this configuration, we obtained a 75%-efficient SRO with a combined signal (19 W @ 1.55 mu m) and idler (11 W @ 3.4 mu m) output power of 30 W.

  • 1395.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pump threshold optimization of a continuous-wave optical parametric oscillator using avariable-reflectivity volume Bragg grating2014Konferensbidrag (Refereegranskat)
  • 1396.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Frequency doubling in Rb:PPKTP of a high-power, continuous-wave, VBG-locked fiber laser2012Konferensbidrag (Refereegranskat)
  • 1397.
    Zeil, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    High-power Continuous-wave Frequency-doubling in KTiOAsO42013Ingår i: Advanced Solid-State Lasers Congress: OSA Technical Digest 2013 / [ed] G. Huber and P. Moulton, Optical Society of America, 2013, s. AM3A.4-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present efficient single-pass second harmonic generation at 533 nm by frequency doubling a high-power continuous wave fiber laser in KTiOAsO4 (KTA). The scheme provided 11.4 W of green power at a conversion efficiency of 25 %.

  • 1398. Zhan, Qiuqiang
    et al.
    Liu, Haichun
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wang, Baoju
    Wu, Qiusheng
    Pu, Rui
    Zhou, Chao
    Huang, Bingru
    Peng, Xingyun
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. South China Normal University, China.
    Achieving high-efficiency emission depletion nanoscopy by employing cross relaxation in upconversion nanoparticles2017Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, nr 1, artikel-id 1058Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Conventionally, stimulated emission depletion requires a relatively high light intensity to obtain an adequate depletion efficiency through only light–matter interaction. Here we show efficient emission depletion for a class of lanthanide-doped upconversion nanoparticles with the assistance of interionic cross relaxation, which significantly lowers the laser intensity requirements of optical depletion. We demonstrate two-color super-resolution imaging using upconversion nanoparticles (resolution ~ 66 nm) with a single pair of excitation/depletion beams. In addition, we show super-resolution imaging of immunostained cytoskeleton structures of fixed cells (resolution ~ 82 nm) using upconversion nanoparticles. These achievements provide a new perspective for the development of photoswitchable luminescent probes and will broaden the applications of lanthanide-doped nanoparticles for sub-diffraction microscopic imaging.

  • 1399.
    Zhang, Feng
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Ai, Yue-Jie
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Fang, Wei-Hai
    Nonadiabatic histidine dissociation of hexacoordinate heme in neuroglobin protein2010Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, density functional theory and canonical nonadiabatic Monte Carlo transition state theory have been used to investigate histidine dissociation process from the hexacoordinate heme in Ngb protein. The potential energy surfaces (PES) of the lowest singlet, triplet, and quintet states are calculated by stepwise optimization along with the histidine dissociation pathway. Based on the calculated two-dimensional PES, the histidine dissociation rates for the spin-forbidden processes via singlet to triplet and singlet to quintet transitions have been calculated by the nonadiabatic Monte Carlo transition state theory in canonical ensemble. The present study provides a quantitative description on spin-forbidden histidine dissociation processes.

  • 1400.
    Zhang, Igor Ying
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Wu, Jianming
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Xu, Xin
    Trends in R-X Bond Dissociation Energies (R-center dot = Me, Et, i-Pr, t-Bu, X-center dot = H, Me, Cl, OH)2010Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, nr 5, s. 1462-1469Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Trends for R X bond dissociation energies have been examined with density functional methods of B3LYP, BMK, M06-2X, MC3MPW, B2PLYP, MCG3-MPW, and XYG3, as well as 03, MCG3/3, G3X, and 04 theories as functions of alkylation (i.e., IT = Me, Et, i-Pr, (-Bu) and X' substitution (i.e., X' = H, Me, Cl, OH). The results highlight the physical origin of success or failure of each method and demonstrate the good agreement with experimental results for G4, MCG3-MPW, and XYG3. The last holds great promise as a reliable method that is applicable to larger systems.

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