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  • 301. Rong, Y.
    et al.
    Ge, Y.
    Huo, Y.
    Fiorentino, M.
    Kamins, T. I.
    Ochalski, T.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chacinski, Marek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Harris, J. S.
    High speed optical modulation in Ge quantum wells using quantum confined stark effect2009In: Group IV Photonics, 2009. GFP '09. 6th IEEE International Conference on, 2009, p. 157-159Conference paper (Refereed)
    Abstract [en]

    We designed the coplanar high-speed modulator with Ge/SiGe quantum wells, and demonstrated 25GHz of modulation with 3.125GHz of eye diagram using quantum-confined stark effect.

  • 302.
    Ruan, Zhichao
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Negative refraction and sub-wavelength imaging through surface waves on periodically structured metal surface2006Conference paper (Refereed)
    Abstract [en]

    The negative refraction of surface waves on a structured metal surface is proposed and demonstrated. Sub-wavelength imaging of a point diploe source through a slab structure is also shown.

  • 303. Saastamoinen, T.
    et al.
    Turunen, J.
    Tervo, J.
    Setala, T.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Electromagnetic coherence theory of laser resonator modes2005In: Journal of the Optical Society of America a-Optics Image Science and Vision, ISSN 1084-7529, Vol. 22, no 1, p. 103-108Article in journal (Refereed)
    Abstract [en]

    A theory of open laser resonators is formulated within the framework of the electromagnetic coherence theory. It is shown that if only one Fox-Li mode contributes to the field at a given frequency. then the field at that frequency is necessarily completely coherent in view of the space- frequency, counterpart of the recently introduced degree of coherence of electromagnetic fields [Opt. Express 11, 1137 (2003)]. It is also shown that the relation between the number of Fox-Li modes and the new degree of coherence is analogous to the relation established in the scalar theory of laser resonator modes. Difficulties that arise with the formerly introduced visibility-based definition of the electromagnetic degree of coherence are briefly discussed.

  • 304.
    Sainz, Isabel
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Combating entanglement sudden death with non-local quantum-error correction2009In: International Journal of Quantum Information, ISSN 0219-7499, Vol. 7, no Suppl. 1, p. 245-255Article in journal (Refereed)
    Abstract [en]

    We study the possibility of preventing finite-time disentanglement caused by dissipation by making use of non-local quantum error correction. This is made in comparison to previous results, where it was shown that local quantum error correction can delay disentanglement, but can also cause entanglement sudden death when it is not originally present.

  • 305.
    Sainz, Isabel
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Klimov, A. B.
    Roa, L.
    Quantum phase transitions in an effective Hamiltonian: fast and slow systems2008In: JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, ISSN 1751-8113, Vol. 41, no 35, p. 355301-Article in journal (Refereed)
    Abstract [en]

    An effective Hamiltonian describing interaction between generic fast and slow systems is obtained in the strong interaction limit. The result is applied for studying the effect of quantum phase transition as a bifurcation of the ground state of the slow subsystem. Examples such as atom-field and atom-atom interactions are analyzed in detail.

  • 306.
    Sainz, Isabel
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Kothe, Christian
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Estimating entanglement through local correlations2007In: ICONO 2007: Physics Of Intense And Superintense Laser Fields; Attosecond Pulses; Quantum And Atomic Optics; And Engineering Of Quantum Information / [ed] Bandrauk, A; Fedorov, MV; Giacobino, E; Kilin, S; Kulik, S; Sandner, W; Sergeev, AM; Sergienko, A, 2007, Vol. 6726, p. E7263-E7263Conference paper (Refereed)
    Abstract [en]

    A bipartite, arbitrary-dimensional entanglement measure based on local correlations of any set of generators of the corresponding algebras is proposed. An explicit relation with the I- and 3-concurrences for pure states, and a limit for entangled mixed states, are given.

  • 307. Sambaraju, R.
    et al.
    Herrera, J.
    Marti, J.
    Zibar, D.
    Caballero, A.
    Jensen, J. B.
    Monroy, I. T.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Walber, A.
    Up to 40 Gb/s wireless signal generation and demodulation in 75-110 GHz band using photonic techniques2010In: Proceedings - 2010 IEEE International Topical Meeting on Microwave Photonics, MWP 2010, 2010Conference paper (Refereed)
    Abstract [en]

    Record wireless signal capacity of up to 40 Gb/s is demonstrated in the 75-110 GHz band. All-optical OFDM and photonic up-conversion are used for generation and digital coherent detection for demodulation.

  • 308.
    Sanatinia, Reza
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Surface Second-Harmonic Generation from Vertical GaP Nanopillars2012In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 12, no 2, p. 820-826Article in journal (Refereed)
    Abstract [en]

    We report on the experimental observation and analysis of second-harmonic generation (SHG) from vertical GaP nanopillars. Periodic arrays of GaP nanopillars with varying diameters ranging from 100 to 250 nm were fabricated on (100) undoped GaP substrate by nanosphere lithography and dry etching. We observed a strong dependence of the SHG intensity on pillar diameter. Analysis of surface and bulk contributions to SHG from the pillars including the calculations of the electric field profiles and coupling efficiencies is in very good agreement with the experimental data. Complementary measurements of surface optical phonons by Raman spectroscopy are also in agreement with the calculated field intensities at the surface. Finally, polarization of the measured light is used to distinguish between the bulk and surface SHG from GaP nanopillars.

  • 309. Schubert, C.
    et al.
    Li, J.
    Bach, H. -G
    Mekonnen, G. G.
    Makon, R. E.
    Derksen, R. H.
    Hurm, V.
    Djupsjöbacka, A.
    Chacinski, Marek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Steffan, A. G.
    Driad, R.
    Characterization of a pin-TWA photoreceiver in OOK-system experiments up to 112 Gb/s2010In: 2010 36th European Conference and Exhibition on: Optical Communication (ECOC), 2010, p. 5621372-Conference paper (Refereed)
    Abstract [en]

    A high-speed pin-TWA photoreceiver, comprising a photodiode and a travelling-wave amplifier, monolithically integrated on a single InP chip, are characterized in OOK system experiments. Error-free performance below the FEC limit is achieved in back-to-back measurements up to 112 Gb/s.

  • 310. Sergeyev, S.
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Influence of the short-range coordination order of erbium ions on excitation migration and upconversion in multicomponent glasses2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 11, p. 1258-1260Article in journal (Refereed)
    Abstract [en]

    Applying a pair-correlation function of erbium ions that is known from x-ray absorption fine structure spectroscopy, we develop a new statistical model of migration-assisted upconversion in erbium-doped glasses. The results of modeling show that short-range coordination order of erbium ions contributes to the upconversion rate for both low and high population inversion. In addition, we report the methods of suppression of the short-range order of erbium ions in multicomponent glasses.

  • 311. Sergeyev, S.
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Modeling polarization-dependent gain in fiber Raman amplifiers with randomly varying birefringence2006In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 262, no 1, p. 114-119Article in journal (Refereed)
    Abstract [en]

    We report a new stochastic model for studying the polarization-dependent gain in Raman fiber amplifiers with randomly varying birefringence as a function of the pump state of polarization and the polarization mode dispersion parameter. Our theoretical results agree with the previously obtained experimental data.

  • 312. Sergeyev, Sergey
    et al.
    O'Mahoney, Kieran
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Upconversion assisted self-pulsing in a high-concentration erbium doped fibre laser2010In: Central European Journal of Physics, ISSN 1895-1082, E-ISSN 1644-3608, ISSN 1895-1082 print, Vol. 8, no 2, p. 159-163Article in journal (Refereed)
    Abstract [en]

    We report results on experimental and theoretical characterisation of self-pulsing in high concentration erbium doped fibre laser which is free from erbium clusters. Unlike previous models of self-pulsing accounting for pair-induced quenching (PIQ) on the clustered erbium ions, new model has been developed with accounting for statistical nature of the excitation migration and upconversion and resonance-like pumpto-signal intensity noise transfer. The obtained results are in a good agreement with the experimental data.

  • 313. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Stochastic model of polarization-dependent gain and gain fluctuations in fiber Raman amplifier with randomly varying birefringence2007In: Laser Optics 2006: Solid State Lasers and Nonlinear Frequency Conversion / [ed] Vladimir I. Ustyugov, SPIE - International Society for Optical Engineering, 2007Conference paper (Refereed)
    Abstract [en]

    We report a new stochastic model for studying the polarization-dependent gain and gain fluctuations in Raman fiber amplifiers with randomly varying birefringence as a function of the pump state of polarization and the polarization mode dispersion parameter. Based on the presented model and our previous experimental data for polarization dependent gain we develop a new experimental technique for birefringence correlation length measurement.

  • 314. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Raman amplification with reduced polarization impairments in the fibre with tailored spin profile2010In: Central European Journal of Physics, ISSN 1895-1082, E-ISSN 1644-3608, ISSN 1895-1082 print, Vol. 8, no 2, p. 164-168Article in journal (Refereed)
    Abstract [en]

    By using two-section fibre where the first section has no spin and the second one is periodically spun, we demonstrate reduced polarization dependent gain and polarization mode dispersion (0.3 dB and 0.0072 ps center dot km(-1/2) correspondently) in a distributed fibre Raman amplifier.

  • 315. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari T.
    Virtually Isotropic Transmission Media With Fiber Raman Amplifier2010In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 46, no 10, p. 1492-1497Article in journal (Refereed)
    Abstract [en]

    We report a theoretical study and simulations of a novel fiber-spin tailoring technique to suppress the polarization impairments, namely polarization mode dispersion and polarization dependent gain (PDG), in fiber Raman amplifiers. Whereas use of depolarizer or multiplexing pump laser diodes with a final degree of pump polarization of 1% for periodically spun fiber results in PDG of about 0.3 dB, we demonstrate that application of just a two-section fiber (where the first part is short and has no spin, and the second one is periodically spun) can reduce the PDG to as low as below 0.1 dB.

  • 316. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Khoptyar, Dmitry
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Flavin, Donal
    Statistical model of migration-assisted upconversion in a high-concentration erbium-doped fiber amplifier2006In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 23, no 8, p. 1540-1543Article in journal (Refereed)
    Abstract [en]

    We report a new model of a high-concentration erbium-doped fiber amplifier (EDFA) accounting for the statistical nature of the migration and up-conversion processes. By fitting experimental results, we conclude that the statistical model shows better applicability for the characterization of high-concentration EDFAs than the model accounting for the homogeneous upconversion and pair-induced quenching.

  • 317. Sergeyev, Sergey V.
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Polarization-dependent gain and gain fluctuations in a fiber Raman amplifier2007In: Journal of Optics. A, Pure and applied optics, ISSN 1464-4258, E-ISSN 1741-3567, Vol. 9, no 12, p. 1119-1122Article in journal (Refereed)
    Abstract [en]

    We report a new vector model of a fiber Raman amplifier with a randomly varying birefringence. We find that the analysis of gain fluctuations and polarization-dependent gain can be used for measurements of beat and birefringence correlation lengths and the polarization mode dispersion value on a long single-mode fiber. Results are consistent with a standard technique based on differential group delay measurements.

  • 318. Sergeyev, S.V
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Two-section fiber optic Raman polarizer for high-speed transmission systems2011In: 2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON) / [ed] Jaworski, M; Marciniak, M, 2011Conference paper (Refereed)
    Abstract [en]

    We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Based on the Stochastic Generator approach we have derived equations for polarization dependent gain and mean-square gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short fiber without spin and properly chosen parameters and a long periodically spun fiber. This polarizer provides almost the same polarization pulling for all input signal states of polarization and so have very small polarization dependent gain. The obtained results can be used in high-speed fiber optic communication for design of quasi-isotropic spatially and spectrally transparent media with increased Raman gain.

  • 319. Setala, T.
    et al.
    Lindberg, J.
    Blomstedt, K.
    Tervo, J.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Coherent-mode representation of a statistically homogeneous and isotropic electromagnetic field in spherical volume2005In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 71, no 3Article in journal (Refereed)
    Abstract [en]

    It is known that statistically stationary, homogeneous, and isotropic source distributions generate, in an unbounded low-loss medium, an electromagnetic field whose electric cross-spectral density tensor is proportional to the imaginary part of the infinite-space Green tensor. Using the recently established electromagnetic theory of coherent modes, we construct, in a finite spherical volume, the coherent-mode representation of the random electromagnetic field having this property. The analysis covers the fundamental case of blackbody radiation but is valid more generally; since a thermal equilibrium condition is not invoked, the electromagnetic field may have any spectral distribution. Within the scalar theory of coherent modes, which has been available for more than two decades, the analogous formulation results in the first explicit three-dimensional coherent-mode representation.

  • 320. Setala, Tero
    et al.
    Lindfors, Klas
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Degree of polarization in 3D optical fields generated from a partially polarized plane wave2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 21, p. 3394-3396Article in journal (Refereed)
    Abstract [en]

    We show that, for 3D random electromagnetic fields that are created by optical systems from a partially polarized plane wave, two different definitions of the 3D degree of polarization proposed in literature have a monotonic one-to-one correspondence, thus providing the same information about the field's polarization state. Examples of 3D fields obeying this result are the evanescent wave generated in total internal reflection, the tightly focused beam, and the far field scattered from an electric point dipole.

  • 321. Setala, Tero
    et al.
    Nunziata, Ferdinando
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Differences between partial polarizations in the space-time and space-frequency domains2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 19, p. 2924-2926Article in journal (Refereed)
    Abstract [en]

    The time-domain degree of polarization of a stationary, random optical beam, in general, differs from that in the frequency domain. We elucidate the origin of their differences and consider several examples in which the two degrees of polarization either are or are not the same.

  • 322. Setala, Tero
    et al.
    Shevchenko, Andriy
    Kaivola, Matti
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Polarization time and length for random optical beams2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 78, no 3Article in journal (Refereed)
    Abstract [en]

    We investigate the dynamics of the instantaneous polarization state of stationary, partially polarized random electromagnetic beamlike fields. An intensity-normalized correlation function of the instantaneous Poincare vector is introduced for the characterization of the time evolution of the polarization state. This polarization correlation function enables us to define a polarization time and a polarization length over which the polarization state remains substantially unchanged. In the case of Gaussian statistics, the polarization correlation function is shown to assume a simple form in terms of the parameters employed to characterize partial coherence and partial polarization of electromagnetic fields. The formalism is demonstrated for a partially polarized, temporally Gaussian-correlated beam, and black-body radiation. The results are expected to find a range of applications in investigations of phenomena where polarization fluctuations of light play an important role.

  • 323. Setala, Tero
    et al.
    Shirai, Tomohiro
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Fractional Fourier transform in temporal ghost imaging with classical light2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 4, p. 043813-Article in journal (Refereed)
    Abstract [en]

    We investigate temporal, second-order classical ghost imaging with long, incoherent, scalar plane-wave pulses. We prove that in rather general conditions, the intensity correlation function at the output of the setup is given by the fractional Fourier transform of the temporal object. In special cases, the correlation function is shown to reduce to the ordinary Fourier transform and the temporal image of the object. Effects influencing the visibility and the resolution are considered. This work extends certain known results on spatial ghost imaging into the time domain and could find applications in temporal tomography of pulses.

  • 324. Setala, Tero
    et al.
    Tervo, Jani
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Contrasts of Stokes parameters in Young's interference experiment and electromagnetic degree of coherence2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, no 18, p. 2669-2671Article in journal (Refereed)
    Abstract [en]

    We analyze the modulation of the Stokes parameters in Young's two-pinhole interference experiment with a random electromagnetic beam. We demonstrate that the electromagnetic (spectral) degree of coherence put forward in Opt. Lett. 29, 328 (2004) [or its space-time analog in Opt. Express 11, 1137 (2003)] is physically related to the contrasts of modulation in the four Stokes parameters. More explicitly, the electromagnetic degree of coherence is a measure of both the visibility of the intensity fringes and the modulation contrasts of the three polarization Stokes parameters. We also show that by using suitable wave plates the modulation in any Stokes parameter can be transformed into the form of intensity variation, and hence the electromagnetic degree of coherence can be obtained experimentally by four visibility measurements.

  • 325. Setala, Tero
    et al.
    Tervo, Jani
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Stokes parameters and polarization contrasts in Young's interference experiment2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, no 14, p. 2208-2210Article in journal (Refereed)
    Abstract [en]

    We derive a spectral interference law that governs the behavior of the four Stokes parameters in Young's two-pinhole experiment with a random electromagnetic beam. In addition to the visibility of intensity fringes, we introduce three new contrast parameters that describe the interference-induced changes in the field's state of partial polarization. The polarization modulation depends on the electric field correlations at the pinholes and is closely related to the two-point Stokes parameters. The results are expected to be particularly useful in polarization interferometry and electromagnetic coherence theory. The formalism is demonstrated with specific examples.

  • 326. Setälä, T.
    et al.
    Hakkarainen, T.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. Aalto University, Espoo, Finland .
    Hoenders, B. J.
    Invisibility cloaking in weak scattering2010In: 2010 9th Euro-American Workshop on Information Optics, WIO 2010, 2010, p. 5582525-Conference paper (Refereed)
    Abstract [en]

    We consider invisibility cloaking of a slab object in scalar wave theory within the first-order Born approximation.We show that in the forward direction cloaking is achieved for any object slab and incident field, whereas in the backward direction cloaking is possible at least for self-imaging fields. In both cases the scattering potential of the cloak slab depends on that of the object slab. The method of object-dependent cloaking using weak slab scatterers can be a useful addition to existing cloaking methods, for instance, in atmospheric optics and biophotonics.

  • 327. Setälä, Tero
    et al.
    Hakkarainen, Timo
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Hoenders, Bernhard J.
    Object-dependent cloaking in the first-order Born approximation2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 1, p. 013814-Article in journal (Refereed)
    Abstract [en]

    We consider the cloaking of a slab object in scalar wave theory within the first-order Born approximation. We show that in the forward direction cloaking is achieved for any transversally invariant, positively refracting, and absorbing object by using a lossy, negative-index metamaterial cloak. Cloaking is perfect and occurs for incident fields having any spatial structure and bandwidth. In the backward direction cloaking is found to be possible for self-imaging fields. In both cases the refractive-index distribution and dispersive properties of the cloak slab resemble those of the object slab. The method of object-dependent cloaking with weak scatterers may find useful applications.

  • 328.
    Shahid, Naeem
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Amin, Muhammad
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Junction-type photonic crystal waveguides for notch- and pass-band filtering2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 21, p. 21074-21080Article in journal (Refereed)
    Abstract [en]

    Evolution of the mode gap and the associated transmission mini stop-band (MSB) as a function of photonic crystal (PhC) waveguide width is theoretically and experimentally investigated. The change of line-defect width is identified to be the most appropriate way since it offers a wide MSB wavelength tuning range. A high transmission narrow-band filter is experimentally demonstrated in a junction-type waveguide composed of two PhC waveguides with slightly different widths. The full width at half maximum is 5.6 nm; the peak transmission is attenuated by only 5 dB and is 20 dB above the MSBs. Additionally, temperature tuning of the filter were also performed. The results show red-shift of the transmission peak and the MSB edges with a gradient of dλ/dT $=$ 0.1 nm/°C. It is proposed that the transmission MSBs in such junction-type cascaded PhC waveguides can be used to obtain different types of filters.

  • 329.
    Shahid, Naeem
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Li, Min Yue
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Novel postetch process to realize high quality photonic crystals in InP2011In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 29, no 3, p. 031202-Article in journal (Refereed)
    Abstract [en]

    Thermally driven reflow of material during annealing was positively used to obtain near-vertical sidewall profiles for high-aspect-ratio nanostructures in InP fabricated by dry etching. This is very promising for achieving high optical quality in photonic crystal (PhC) components. Nearly cylindrical profiles were obtained for high-aspect-ratio PhC holes with diameters as small as 200350 nm. Mini stop bands (MSBs) in line-defect PhC waveguides were experimentally investigated for both as-etched and reshaped hole geometries, and their spectral characteristics were used to assess the quality of PhC fabrication. The spectral characteristics of the MSB in PhC waveguides with reshaped holes showed significant improvement in performance with a transmission dip as deep as 35 dB with sharp edges dropping in intensity more than 30 dB for similar to 4 nm of wavelength change. These results show potential for using high extinction drop-filters in InP-based monolithic photonic integrated circuit applications. Finally, it is proposed that other nanostructure geometries may also benefit from this reshaping process.

  • 330.
    Shahid, Naeem
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Speijcken, Noud
    KTH, School of Information and Communication Technology (ICT).
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Li, Mingyu
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Ultrasharp ministop-band edge for subnanometer tuning resolution2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 8, p. 081112-Article in journal (Refereed)
    Abstract [en]

    We propose and demonstrate a method that enables spectral tuning with subnanometer accuracy, and is based on the transmission ministop-band (MSB) in line-defect multimode photonic crystal (PhC) waveguides. The fabricated MSB filter has ultrasharp edges which show a 30 dB drop in transmission in a 4 nm wavelength span. The use of the ultrasharp MSB edge to (optically) determine PhC fabrication accuracy is demonstrated. The wavelength position of the MSB could be tuned by temperature, with a coefficient of 0.1 nm/degrees C. The spectral characteristics of the MSB realized in this work are promising for sensing, tuning, and modulation applications.

  • 331. Shirai, T.
    et al.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Resolution improvement in spectral-domain optical coherence tomography based on classical intensity correlations2013In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 38, no 2, p. 115-117Article in journal (Refereed)
    Abstract [en]

    We describe a resolution-improved spectral-domain (SD) optical coherence tomography (OCT) based on classical intensity correlations as a counterpart of the recently proposed intensity-based time-domain OCT. Similarly to quantum OCT, the setup employs the Hong-Ou-Mandel interferometer at the output of the conventional SD-OCT. It is shown theoretically that a factor-of-√2 improvement in axial resolution is obtained with this arrangement. Some unique and useful features of our proposed system are addressed.

  • 332. Shirai, T.
    et al.
    Kellock, H.
    Setälä, T.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics. Aalto University, FI-00076 Aalto, P. O. Box 13500, Finland; University of Eastern Finland, FI-80101 Joensuu, P. O. Box 111, Finland.
    Fourier synthesis in classical ghost imaging2011In: Proceedings of Applied Industrial Optics: Spectroscopy, Imaging and Metrology, AIO 2011, The Optical Society , 2011Conference paper (Refereed)
    Abstract [en]

    We describe an optical setup for performing spatial Fourier filtering in ghost imaging with classical incoherent light. It is shown that phase contrast imaging is possible with this setup to visualize a pure phase object.

  • 333. Shirai, T.
    et al.
    Setälä, T.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. Aalto University, Espoo, Finland .
    Some features of temporal ghost imaging with classical light2010In: 2010 9th Euro-American Workshop on Information Optics, WIO 2010, 2010, p. 5582506-Conference paper (Refereed)
    Abstract [en]

    Temporal ghost imaging with classical pulsed light is described as a temporal counterpart of conventional ghost imaging with thermal light. A temporal object to be imaged is located in the test arm while the reference arm consists of some simple temporal optical elements. The incident light is assumed to be temporally incoherent, classical pulsed light.We first show that the correlation between intensity fluctuations in these two arms is given by a fractional Fourier transform of the temporal object. In special cases, the fractional Fourier transform reduces to the ordinary Fourier transform and the image of the object. We then derive explicit expressions for the resultant ghost image under two different conditions, with a view to examining the effect of the incident pulse. As a result, it is found that the resultant temporal ghost image depends only on the single temporal variable in the reference arm though the light in this arm never interacts with the object, and that it is generally distorted by the effect of the incident pulse.

  • 334. Shirai, Tomohiro
    et al.
    Kellock, Henri
    Setälä, Tero
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Visibility in ghost imaging with classical partially polarized electromagnetic beams2011In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, no 15, p. 2880-2882Article in journal (Refereed)
    Abstract [en]

    We consider classical second-order ghost imaging with uniformly partially polarized electromagnetic beams and examine the effect of the degree of polarization of the incident light on the visibility of the image. Closed-form expressions for two previously proposed definitions of visibility are derived. Both results are physically similar and show that the visibility increases with the degree of polarization. Hence, a polarized beam is superior to an unpolarized one to obtain a high-visibility ghost image. Some related issues in recent literature are also addressed.

  • 335. Silfvenius, C.
    et al.
    Swillo, M.
    Claesson, J.
    Forsberg, E.
    Akram, N.
    Chacinski, Marek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    InP-based monolithically integrated 1310/1550nm diplexer/triplexer2008In: Proceedings of SPIE - The International Society for Optical Engineering, 2008Conference paper (Refereed)
    Abstract [en]

    We demonstrate a low cost, non-butt-joint, wide-gain integrated device comprising 1550nm lasers, wavelength selective couplers and 1310nm sensitive photodiodes for diplexer arrays for FTTH use.

  • 336. Skorin-Kapov, Nina
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    A New Approach to Optical Networks Security: Attack-Aware Routing and Wavelength Assignment2010In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 18, no 3, p. 750-760Article in journal (Refereed)
    Abstract [en]

    Security issues and attack management in transparent wavelength division multiplexing (WDM) optical networks have become of prime importance to network operators due to the high data rates involved and the vulnerabilities associated with transparency. Deliberate physical-layer attacks, such as high-powered jamming, can seriously degrade network performance and must be dealt with efficiently. While most approaches are focused on the developing fast detection and reaction mechanisms triggered in case of an attack, we propose a novel approach to help deal with these issues in the network planning and provisioning process as a prevention mechanism. Namely, we propose to route lightpaths in such a way as to minimize the potential damage caused by various physical-layer attacks. We present a new objective criterion for the routing and wavelength assignment (RWA) problem, which we call the maximum Lightpath Attack Radius (maxLAR), and formulate the routing subproblem as an integer linear program (ILP). We test it on small networks to get an insight into its complexity and compare it to a formulation that minimizes congestion. Results indicate that our formulation achieves significantly better results for the maxLAR while obtaining near-optimal or optimal congestion in all cases. For larger networks, we propose a tabu search algorithm for attack-aware lightpath routing, in combination with an existing graph-coloring algorithm for wavelength assignment. Testing and comparing with existing approaches from literature indicate its superiority with respect to the maxLAR and average lightpath load, albeit at the expense of somewhat higher congestion. However, this is justified with the obtained improvement in network security.

  • 337.
    Skorin-Kapov, Nina
    et al.
    Zagreb University.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    A tabu search algorithm for attack-aware lightpath routing2008In: ICTON 2008: PROCEEDINGS OF 2008 10TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOL 3 / [ed] Marciniak, M, NEW YORK: IEEE , 2008, p. 42-45Conference paper (Other academic)
    Abstract [en]

    Attacks in Transparent Optical Networks present a serious security threat to Successful network operation due to the high data rates involved and the vulnerabilities associated with transparency. Typical physical layer attacks can involve injecting high-powered jamming signals on legitimate data channels to exploit Vulnerabilities in optical components Such as crosstalk in switches and fibers, and gain competition in amplifiers. To assure a certain quality of service in the network, we propose a novel approach which considers Such security threats during the network planning process. More specifically, we propose a tabu search heuristic aimed to perform lightpath routing in Such a way as to minimize the possible 'reachability' of a jamming attack with respect to gain competition and inter-channel crosstalk. In this way we limit the worst case scenario which can potentially be caused by such an attack. We tested the algorithm on the 14-node NSF network and compare with shortest path routing. The algorithm not only yields better attack protection, but reduces lightpath congestion and minimizes the upper bound on the number of wavelengths needed for wavelength assignment.

  • 338. Skubic, Björn
    et al.
    Chen, Biao
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Improved scheme for estimating T-CONT bandwidth demand in status reporting DBA for NG-PON2009In: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009, Vol. 2009-SupplementConference paper (Refereed)
    Abstract [en]

    A scheme for estimating T-CONT bandwidth demand within dynamic bandwidth allocation (DBA) for next-generation passive optical network (NG-PON) is proposed and evaluated. Estimating T-CONT bandwidth demand is considered as a main challenge in gigabit-capable passive optical network (GPON) DBA. The proposed minimum guaranteed T-CONT content (MGTC) scheme allows for a more conservative estimate of bandwidth demand. It is shown that at high load significant improvements in delay, jitter and bandwidth utilization can be achieved with the proposed scheme. For light loads the conventional scheme shows better delay performance. However, this may be overcome by controlled over-granting in the MGTC scheme.

  • 339. Skubic, Björn
    et al.
    Chen, Biao
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. Zhejiang University, China.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Improved scheme for estimating T-CONT bandwidth demand in status reporting DBA for NG-PON2009In: Network Architectures, Management, and Applications VII, SPIE - International Society for Optical Engineering, 2009, p. 76330E-Conference paper (Refereed)
    Abstract [en]

    A scheme for estimating T-CONT bandwidth demand within dynamic bandwidth allocation (DBA) for next-generation passive optical network (NG-PON) is proposed and evaluated. Estimating T-CONT bandwidth demand is considered as a main challenge in gigabit-capable passive optical network (GPON) DBA. The proposed minimum guaranteed T-CONT content (MGTC) scheme allows for a more conservative estimate of bandwidth demand. It is shown that at high load significant improvements in delay, jitter and bandwidth utilization can be achieved with the proposed scheme. For light loads the conventional scheme shows better delay performance. However, this may be overcome by controlled overgranting in the MGTC scheme.

  • 340. Skubic, Björn
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Biao
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Mukherjee, Biswanath
    Dynamic Bandwidth Allocation for Long-Reach PON: Overcoming Performance Degradation2010In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 48, no 11, p. 100-108Article in journal (Refereed)
    Abstract [en]

    A passive optical network, with its inherent point to multi-point structure, allows for centralized placement of active equipment and possible extension of its boundary towards core networks. This property of the PON can be exploited for node consolidation where multiple central offices are replaced by a single one covering a larger service area. Such node consolidation is being particularly driven by the need for network operational cost saving, and is offering significant challenges to PONs. The degree of node consolidation that can be achieved is limited by the reach of conventional PON systems. In order to achieve a larger degree of node consolidation, an extension of the PON reach, beyond the conventional 20 km, is required. This article addresses the challenges of the dynamic bandwidth allocation, where increased reach results in a degradation of DBA performance and quality of service support. This degradation is a consequence of the increased propagation delay of the DBA messages exchanged between different PON elements. A potential solution to the performance degradation is the introduction of a multi-threaded DBA. In this article, we examine for both Gigabit PON and Ethernet PON, the extent to which DBA performance degradation can be reduced by exploiting multi-threading. It is found that for both standards, multi-threading, if done properly, can be used to mitigate the performance degradation due to the increased reach. To make bandwidth allocation efficient, new schemes for coordinating the multiple threads are required in long reach PON.

  • 341.
    Skubic, Björn
    et al.
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Biao
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Dynamic bandwidth allocation in EPON and GPON2010In: Convergence of Mobile and Stationary Next-Generation Networks / [ed] Krzysztof Iniewski, John Wiley & Sons, 2010Chapter in book (Refereed)
  • 342. Smith, David A.
    et al.
    Aigner, Simon
    Hofferberth, Sebastian
    Gring, Michael
    Andersson, Mauritz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wildermuth, Stefan
    Krueger, Peter
    Schneider, Stephan
    Schumm, Thorsten
    Schmiedmayer, Joerg
    Absorption imaging of ultracold atoms on atom chips2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 9, p. 8471-8485Article in journal (Refereed)
    Abstract [en]

    Imaging ultracold atomic gases close to surfaces is an important tool for the detailed analysis of experiments carried out using atom chips. We describe the critical factors that need be considered, especially when the imaging beam is purposely reflected from the surface. In particular we present methods to measure the atom-surface distance, which is a prerequisite for magnetic field imaging and studies of atom surface-interactions.

  • 343.
    Song, Yi
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Plasmonic waveguides and resonators for optical communication applications2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Photonic circuits can transmit data signals in a much higher speed thanconventional electronic circuits. However, miniaturization of photonic circuitsand devices is hindered by the existence of light diffraction limit. A promisingsolution to this problem is by exploiting plasmonic systems for guiding andmanipulating signals at optical frequencies. Plasmonic devices are generallycomposed of noble metals and dielectrics, whose interfaces can confine surfaceplasmon polaritons, a hybrid wave that is free of diffraction limit. Plasmonicwaveguides and devices are serious contenders for achieving next-generationphotonic integrated circuits with a density comparable to the electronic counterpart.

    This thesis addresses the design issues of passive plasmonic devices whichare critical for realization of photonic integration, including plasmonic waveguides,splitters, couplers, and resonators, investigated with both the finitedifferencetime-domain method and the finite-element method. In particularwe present, firstly, a coupler which efficiently couples light between a silicondielectric waveguide and a hybrid plasmonic (HP) waveguide. A coupling efficiencyas high as 70% is realized with a HP taper as short as 0.4μm. Theexperimental result agrees well with the numerical simulation. Secondly, wenumerically investigate and optimize the performances of 1×2 and 1×3 HPmultimode interferometers (MMIs), which split light from a silicon waveguideto multiple HP waveguides. Total transmission over 75% can be achieved inboth cases. Thirdly, we study the coupling and crosstalk issues in plasmonicwaveguide systems. Several methods for crosstalk reduction are proposed.Finally, HP nanodisk micro-cavities are designed and are numerically characterized.With a radius of 1μm, a high quality factor of 819 and a highPurcell factor of 1827 can be simultaneously achieved, which can be useful forrealizing efficient nano-lasers.

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  • 344.
    Song, Yi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Li, Qiang
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Broadband coupler between silicon waveguide and hybrid plasmonic waveguide2010In: Optics Express, E-ISSN 1094-4087, Vol. 18, no 12, p. 13173-13179Article in journal (Refereed)
    Abstract [en]

    Efficient broadband coupling of light between a dielectric waveguide and a hybrid plasmonic waveguide is investigated theoretically. A plasmonic linear taper is used as a coupler which connects the two types of waveguides. Broadband coupling is realized by such a compact plasmonic taper with a length of only 0.4 mu m, which achieves a coupling efficiency of 70% (1.5dB) at the 1.55 mu m telecommunication wavelength. (C) 2010 Optical Society of America

  • 345.
    Song, Yi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Efficient coupling between dielectric and hybrid plasmonic waveguides by multimode interference power splitter2011In: Journal of optics, ISSN 0150-536X, Vol. 13, no 7, p. 075002-Article in journal (Refereed)
    Abstract [en]

    Multimode interference power splitters based on hybrid plasmonic waveguides are investigated theoretically. Balanced power splitting is achieved in designed 1 × 3 and 1 × 2 power splitters between a silicon-on-insulator waveguide and several hybrid plasmonic waveguides, with total transmission efficiencies at 76.1% and 78.3% at the wavelength of 1550 nm, respectively.

  • 346.
    Song, Yi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Subwavelength hybrid plasmonic nanodisk with high Q factor and Purcell factor2011In: Journal of optics, ISSN 0150-536X, Vol. 13, no 7, p. 075001-Article in journal (Refereed)
    Abstract [en]

    Optical nanodisk resonators based on a hybrid plasmonic waveguiding geometry areinvestigated theoretically in the wavelength range of 1200–2000 nm with their radii varyingfrom 320 to 1000 nm. Due to the fact that a hybrid plasmonic structure can efficiently confinelight in a deep-subwavelength mode volume with a relatively low propagation loss, thenanodisks designed exhibit simultaneously a high Q factor and a high Purcell factor. For ahybrid plasmonic nanodisk with the radius of 1000 nm, a Q factor of 819 and a Purcell factor of1827 are achieved at the telecommunication wavelength of 1558 nm.

  • 347.
    Song, Yi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yang, Qing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Tong, Li-min
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Reducing crosstalk between nanowire-based hybrid plasmonic waveguides2011In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, no 1, p. 480-484Article in journal (Refereed)
    Abstract [en]

    Hybrid plasmonic waveguides based on a surface oxidized dielectric nanowire placed on a metal surface can facilitate simultaneously deep subwavelength mode confinement and large propagation length. Directional coupling based on such waveguides are theoretically investigated. Much lower crosstalk is noticed for such hybrid plasmonic waveguides compared to conventional waveguides based on bare dielectric nanowires. Some modifications, such as vertically placing the metal surfaces or using a metallic block between the nanowires, are studied which can further reduce the crosstalk between two waveguides. The proposed low crosstalk structures based on hybrid plasmonic waveguides can provide a simple platform for plasmonic integration which can at the same time easily interface with traditional photonic circuits. (C) 2010 Elsevier B.V. All rights reserved.

  • 348.
    Sudirman, Azizahalhakim
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Reflectometry, ablation and fluid retrieval with an optical fiber2010In: Optics Express, E-ISSN 1094-4087, Vol. 18, no 1, p. 134-140Article in journal (Refereed)
    Abstract [en]

    A technique combining low-coherence reflectometry, laser ablation and microfluidics in a single microstructured fiber is developed. Experimental results demonstrate the possibility to ablate thin aluminum foil samples with fiber-guided Nd:YAG laser light, to collect liquid in the holes of the fiber and to simultaneously monitor the positioning of fiber for ablation and the fluid collection process with low-coherence reflectometry. Potential applications of the technique include minimally invasive retrieval of liquid samples with low contamination risk.

  • 349.
    Sugunan, Abhilash
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Zhao, Yichen
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Mitra, Somak
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Dong, Lin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis of tetrahedral quasi-type-II CdSe-CdS core-shell quantum dots2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 42, p. 425202-Article in journal (Refereed)
    Abstract [en]

    Synthesis of colloidal nanocrystals of II-VI semiconductor materials has been refined in recent decades and their size dependent optoelectronic properties have been well established. Here we report a facile synthesis of CdSe-CdS core-shell heterostructures using a two-step hot injection process. Red-shifts in absorption and photoluminescence spectra show that the obtained quantum dots have quasi-type-II alignment of energy levels. The obtained nanocrystals have a heterostructure with a large and highly faceted tetrahedral CdS shell grown epitaxially over a spherical CdSe core. The obtained morphology as well as high resolution electron microscopy confirms that the tetrahedral shell have a zinc blende crystal structure. A phenomenological mechanism for the growth and morphology of the nanocrystals is discussed.

  • 350. Suomalainen, Soile
    et al.
    Guina, Mircea
    Hakulinen, Tommi
    Okhotnikov, Oleg
    Euser, T.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    1 µm saturable absorber with recovery time reduced by lattice mismatch2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 7, p. 071112-1-071112-3Article in journal (Refereed)
    Abstract [en]

    Metamorphic growth of lattice mismatched InGaP on GaAs has been used to fabricate a fast semiconductor saturable absorber mirror operating at the 1060 nm wavelength range. The absorption recovery time could be reduced to 5 ps without deteriorating the nonlinear absorption properties. The device was used to demonstrate self-starting operation of a mode-locked Yb-doped fiber laser and obtain high quality picosecond pulses

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