The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform

Chun Jiang - One of the best experts on this subject based on the ideXlab platform.

  • Ultra-wide band dispersionless slow light waveguides
    Optical and Quantum Electronics, 2017
    Co-Authors: Xuemei Chen, Fanghua Wang, Ke Wang, Chun Jiang
    Abstract:

    In conventional slow light waveguide, the delay time of signal in a waveguide is inversely proportional to its bandwidth. As a measure of storage density of optical pulse, the delay-bandwidth product is limited to a small constant depending on waveguiding approach. Breaking the limit is fundamental problem in optical signal and quantum information processing fields. The solution to this problem is becoming increasingly important, especially with high-speed signal processing system. So far, there have been neither practical nor realizable techniques that can solve this problem. In this paper, we propose a mechanism to explore the possibility for breaking the delay-bandwidth limit by using ultra-flat photonic band cluster. We show that based on multiple micro-cavities having corresponding multiple ultra-flat photonic bands, a slow light with arbitrary bandwidth in frequency can be achieved with ultraslow group velocity and ultralow group velocity dispersion, leading to a broken delay-bandwidth limit. This work demonstrates that arbitrary bandwidth dispersionless slow light can be realized with a two-dimensional multiple-microcavity photonic-Crystal Line-Defect waveguide.

  • Slow Light and Dispersion Compensation by Cascading Two Photonic Crystal Waveguides
    International Journal of Modern Physics B, 2014
    Co-Authors: Ye Liu, Bo Fang, Lili Wang, Chun Jiang
    Abstract:

    In this paper, we propose a structure with cascaded two photonic Crystal Line-Defect waveguides to reduce group velocity dispersion (GVD) of slow light. The width of the Line-Defect waveguides is tuned to obtain the two matched dispersion relations, where one of the dispersion relations has a maximum point with zero group velocity and large positive GVD; the other has a minimum point with zero group velocity and large negative GVD. The waveguides have ultra slow light with the group velocity 0.0012c. Finite-difference time-domain simulation demonstrates that the spreading of the slow light pulse in the first waveguide can be recovered by the dispersion compensation of the second waveguide with positive GVD.

  • Wideband ultralow high-order-dispersion photonic Crystal slow-light waveguide
    Journal of the Optical Society of America B, 2011
    Co-Authors: Lei Dai, Chun Jiang
    Abstract:

    We propose a two-dimensional photonic Crystal Line-Defect waveguide, in which the two rows of air holes at the two sides of the Line Defect are infiltrated with dielectric materials. This waveguide exhibits an ultralow high-order-dispersion photonic band. Finite-difference time-domain simulation shows that ultralow high-order dispersion makes an ultrashort Gaussian pulse with width of 0.711 ps or even shorter, to 0.267 ps, propagate without observable pulse broadening and amplitude decrease in a 96 μm long waveguide. The slow light with group velocity of 0.0239 c in a very wide bandwidth of 1.876 THz can theoretically propagate as far as 711 μm with tolerable spread.

  • Enhanced parametric amplification in slow-light photonic Crystal waveguides
    Chinese Science Bulletin, 2009
    Co-Authors: Yang Liu, Chun Jiang
    Abstract:

    We demonstrate both theoretically and numerically that slow light can enhance the parametric process of silicon in photonic Crystal Line-Defect waveguides. Specifically, to get the desired gain, the pump power for a given gain medium length or the gain medium length for given pump power can be reduced by (c/v g n)2 when slow light waveguides are used, where n is the material index of conventional waveguide, v g is the group velocity of the slow light waveguide and c is the light velocity in vacuum.

  • Photonic Crystal slow light waveguides with large delay-bandwidth product
    Applied Physics B, 2009
    Co-Authors: Lei Dai, Chun Jiang
    Abstract:

    In this paper, we propose the use of two two-dimensional photonic Crystal Line Defect waveguides for slow light with large delay–bandwidth product (DBP). One includes air rings localized at each side of the Line Defect and the other modifies the radius and distance of holes at each side of the waveguide. We show that we can achieve a very flat band corresponding to nearly constant group index over a broad frequency range by adjusting the parameters of the structure. We show further that the group velocity dispersion (GVD) can reach a relatively small amount and the DBP can be more than 0.6 for the first waveguide and 0.34 for the second waveguide. Numerical simulation by the finite-difference time-domain (FDTD) method demonstrates the propagation of the broadband pulse.

Kiyoshi Asakawa - One of the best experts on this subject based on the ideXlab platform.

  • NONLineAR OPTICAL EFFECTS IN PHOTONIC-Crystal SLAB Line-Defect WAVEGUIDE FOR ULTRAFAST ALL-OPTICAL SWITCH
    Journal of Nonlinear Optical Physics & Materials, 2011
    Co-Authors: Hisaya Oda, Akio Yamanaka, Naoki Ikeda, Yoshimasa Sugimoto, Kiyoshi Asakawa
    Abstract:

    In order to develop an ultra fast all-optical switch, we have studied optical Kerr effect and two photon absorption in photonic Crystal Line Defect waveguides. Based on these results, we have succeeded in all-optical Mach-Zehnder interferometer switching.

  • Light amplification by stimulated Raman scattering in AlGaAs-based photonic-Crystal Line-Defect waveguides
    Applied Physics Letters, 2008
    Co-Authors: Hisaya Oda, Akio Yamanaka, Naoki Ikeda, Yoshimasa Sugimoto, Kuon Inoue, Kiyoshi Asakawa
    Abstract:

    The authors performed an amplification experiment of optical signal around 1550 nm by stimulated Raman scattering in a photonic-Crystal slab waveguide (WG) of single-Line Defect. They adopted an air-bridge type AlGaAs-based WG sample to avoid two-photon absorption. Short light pulses of 5 ps in duration operated at 20 MHz and a cw laser were employed for pump (excitation) and probe (signal) lights, respectively. As a result, amplification of a net gain of ∼3 dB (maximum) is achieved with pulse pump energy of 22 pJ for a sample of 1.0 mm in length.

  • InAs quantum-dot laser utilizing GaAs photonic-Crystal Line-Defect waveguide.
    Optics express, 2004
    Co-Authors: Kuon Inoue, Naoki Ikeda, Yoshimasa Sugimoto, Hidekazu Sasaki, Koji Ishida, Yu Tanaka, Shunsuke Ohkouchi, Yusui Nakamura, Kiyoshi Asakawa
    Abstract:

    We have observed laser action from optically-pumped InAs-quantum-dots embedded in a Line-Defect waveguide in an air-bridge type GaAs-photonic-Crystal slab (an array of air-holes). The lasing is found to occur without any optical cavity such as a set of Fabry-Perot mirrors. Comparison of the observed transmittance spectrum with the calculated band dispersion of the W3 Defect-mode enables us to specify the lasing wavelength as that at the band edge. From this fact it follows that distributed feedback mechanism at the band edge with a vanishingly small group-velocity should be responsible for the present lasing. Usefulness of this kind of compact laser in a future ultrafast planar photonic integrated circuit is discussed.

Manfred Eich - One of the best experts on this subject based on the ideXlab platform.

  • Disorder limits in passive and amplifying slow light waveguides
    2009 6th IEEE International Conference on Group IV Photonics, 2009
    Co-Authors: Alexander Yu. Petrov, Michael Krause, Jan Hendrik Wülbern, Jan Hampe, Manfred Eich
    Abstract:

    We present a simulation approach to estimate the effect of disorder induced backscattering in slow light photonic Crystal Line-Defect waveguides. The backscattering leads to localization and thus limits the maximal length of such waveguides. Loss in passive waveguides in the localization regime reduces ripples in spectral transmission and group delay whereas gain increases these resonant multiple scattering effects.

  • Low reflection double stage coupling to slow light waveguides
    2008 5th IEEE International Conference on Group IV Photonics, 2008
    Co-Authors: A. Yu. Petrov, Jan Hampe, Manfred Eich
    Abstract:

    Photonic Crystal Line-Defect waveguides can guide optical modes with substantially reduced group velocity. Efficient coupling to slow light waveguides from silicon strip waveguides can be achieved through double stage mode conversion. First, light is coupled to a normal group velocity Line-Defect waveguide with anti-reflection adjustment of the photonic Crystal interface. The reflected intensity at the first stage was reduced to -35 dB in this paper. Second stage consists of the abrupt change to slow light waveguide with intensity reflection about -20 dB for the mode with group velocity 0.02 c. The reflection at the second stage can be further reduced with adiabatic coupling. A gradual tapering 20 lattice constants long with a cubic taper function leads to less than -40 dB intensity reflection for the investigated mode.

  • Broadband Slow Light and NonLinear Switching Devices
    PIERS Online, 2007
    Co-Authors: A. Maitra, Manfred Eich, Alexander Petrov, J. Wang, Juerg Leuthold, Wolfgang Freude
    Abstract:

    In this presentation two classes of compact waveguide structures with functional- ities important in high-speed telecommunication networks are reviewed: The flrst one demon- strates slowing-down of light to 4% of the vacuum speed of light in a photonic Crystal Line-Defect waveguide (PC-LDWG). A fabrication-tolerant bandwidth of 1300 GHz for carriers in the 200THz range is shown both in 3D-simulations and upscaled microwave experiments. The second class introduces optically bistable and direction-dependant transmission in nonLinear materials for stopband-tapered waveguide Bragg gratings (ST-WBG). Optical switching powers of less than 2.7mW are required to achieve an optical isolation ratio of 11 within 300"m propagation through an active material. DOI: 10.2529/PIERS061007085142

  • Broadband Slow Light in a Photonic Crystal Line Defect Waveguide
    Slow and Fast Light, 2006
    Co-Authors: J.-m. Brosi, Wolfgang Freude, Jürg Leuthold, Alexander Petrov, Manfred Eich
    Abstract:

    Pulse transmission at 4% of the vacuum light velocity is shown for a slow-light Line-Defect waveguide with 1300GHz bandwidth. We prove the concept for an upscaled microwave model with disorder both theoretically and experimentally.

  • Large second order dispersion in periodical and aperiodical photonic Crystal waveguides
    Nanophotonics for Communication: Materials and Devices II, 2005
    Co-Authors: Alexander Yu. Petrov, Manfred Eich
    Abstract:

    The second order dispersion is proportional to the difference of time delays accumulated by waves of two adjacent wavelengths. This time delay difference can be obtained when the group velocity or the propagation distance is changing with wavelength. In both cases, a decrease of the smallest available group velocity leads to a proportional size reduction given a fixed dispersion value. In conventional waveguides the smallest group velocity is close to the speed of light in the core material, whereas in photonic Crystal Line-Defect waveguides orders of magnitude smaller group velocities can be obtained within a certain bandwidth. Based on these waveguides, different concepts are proposed and evaluated. A large difference in group velocities for different wavelengths is obtained by anti-crossing of modes in single and coupled Line-Defect waveguides. Alternatively, in chirped photonic Crystal waveguides the path difference, hence the group delay, is strongly varied for adjacent wavelengths. Positive and negative dispersion of approximately hundred ps/nm on millimeter scale over the bandwidth of a single WDM channel (0.8nm) are theoretically predicted and demonstrated using finite integration simulations.

Chee Wei Wong - One of the best experts on this subject based on the ideXlab platform.

  • Enhanced stimulated Raman scattering in slow-light photonic Crystal waveguides
    Optics letters, 2006
    Co-Authors: James F. Mcmillan, Xiaodong Yang, Nicolae C. Panoiu, Richard M. Osgood, Chee Wei Wong
    Abstract:

    We investigate for the first time the enhancement of the stimulated Raman scattering in slow-light Silicon-on-Insulator (SOI) photonic Crystal Line Defect waveguides. By applying the Bloch-Floquet formalism to the guided modes in a planar photonic Crystal, we develop a formalism that relates the intensity of the down-shifted Stokes signal to the pump intensity and the modal group velocities. The formalism is then applied to two prospective schemes for enhanced stimulated Raman generation in slow-light photonic Crystal waveguides. The results demonstrate a maximum factor of 10^4 (66,000) enhancement with respect to SOI channel waveguides. Effects of two photon absorption, intrinsic scattering, and disorder with respect to slow-light Raman generation towards optically-pumped silicon amplifiers and lasers are also discussed.

Yasuhiko Arakawa - One of the best experts on this subject based on the ideXlab platform.

  • A Highly Efficient Optical Add-Drop Multiplexer Using Photonic Band Gap with Hexagonal Hole Lattice Photonic Crystal Slab Waveguides
    IEICE Transactions on Electronics, 2007
    Co-Authors: Akiko Gomyo, Hirohito Yamada, Tao Chu, Satomi Ishida, Jun Ushida, Yasuhiko Arakawa
    Abstract:

    We report on a channel drop filter with a mode gap in the propagating mode of a photonic Crystal slab that was fabricated on silicon on an insulator wafer. The results, simulated with the 3-dimensional finite-difference time-domain and plane-wave methods, demonstrated that an index-guiding mode for the Line Defect waveguide of a photonic Crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector that propagates the light-wave through the Line Defect waveguide, and can be used as an optical filter. The filter bandwidth was varied from 1–8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550–1600 nm. We fabricated a Bragg reflector with a photonic Crystal Line-Defect waveguide and Si-channel waveguides and by measuring the transmittance spectrum found that the Bragg reflector caused abrupt dips in transmittance. These experimental results are consistent with the results of the theoretical analysis described above. Utilizing the Bragg reflector, we fabricated channel dropping filters with photonic Crystal slabs connected between channel waveguides and demonstrated their transmittance characteristics. They were highly drop efficient, with a flat-top drop-out spectrum at a wavelength of 1.56 μm and a drop bandwidth of 5.8 nm. Results showed that an optical add-drop multiplexer with a 2-D photonic Crystal will be available for application in WDM devices for photonic networks and for LSIs in the near future. key words: photonic Crystal, optical add-drop multiplexer, channeLine Defect drop filter, Line-Defect waveguide, Bragg reflector, optical add-drop multiplexer, optical add-drop multiplexer

  • Optical add-drop multiplexer with hexagonal-hole lattice PC slab waveguides
    Optomechatronic Micro Nano Devices and Components II, 2006
    Co-Authors: Akiko Gomyo, Hirohito Yamada, Tao Chu, Satomi Ishida, Jun Ushida, Masayuki Shirane, Yasuhiko Arakawa
    Abstract:

    We report on a channel drop filter with a mode gap in the propagating mode of a photonic Crystal slab that was fabricated on silicon on an insulator wafer. The results, simulated with the 3-dimensional finite-difference time-domain and plane-wave methods, demonstrated that an index-guiding mode for the Line Defect waveguide of a photonic Crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector that propagates the light-wave through the Line Defect waveguide, and can be used as an optical filter. The filter bandwidth was varied from 1-8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550-1600 nm. We fabricated a Bragg reflector with a photonic Crystal Line-Defect waveguide and Si-channel waveguides and by measuring the transmittance spectrum found that the Bragg reflector caused abrupt dips in transmittance. These experimental results are consistent with the results of the theoretical analysis described above. Utilizing the Bragg reflector, we fabricated channel dropping filters with photonic Crystal slabs connected between channel waveguides and demonstrated their transmittance characteristics. They were highly drop efficient, with a flattop drop-out spectrum at a wavelength of 1.56 μm and a drop bandwidth of 5.8 nm. Results showed that an optical adddrop multiplexer with a 2-D photonic Crystal will be available for application in WDM devices for photonic networks and for LSIs in the near future.

  • Observation of micromechanically controlled tuning of photonic Crystal Line-Defect waveguide
    Applied Physics Letters, 2006
    Co-Authors: Satoshi Iwamoto, Masatoshi Tokushima, Hirohito Yamada, Satomi Ishida, Yasuhiko Arakawa, Akiko Gomyo, Akio Higo, Hiroshi Toshiyoshi, Hiroyuki Fujita
    Abstract:

    We fabricated a photonic Crystal (PC) Line-Defect waveguide integrated with a microelectromechanical actuator and demonstrated the optical switching operation. The device consisted of a PC Line-Defect waveguide fabricated in a silicon-on-insulator substrate and a polyCrystalLine-Si dielectric plate located above the PC waveguide. An applied voltage moved the dielectric plate towards the PC surface due to the electrostatic force. This motion increased out-of-plane scattering of the guided light through the evanescent interaction with the dielectric plate, and modulated the transmittance of the PC waveguide. With only a 5μm interaction length, an extinction ratio of ∼10dB was obtained at a wavelength of 1568nm under an applied voltage of 60V. The response time of the switching operation was approximately 1ms.

  • Tunable Optical Notch Filter Realized by Shifting the Photonic Bandgap in a Silicon Photonic Crystal Line-Defect Waveguide
    IEEE Photonics Technology Letters, 2006
    Co-Authors: Tao Chu, Hirohito Yamada, Satomi Ishida, Akiko Gomyo, Jun Ushida, Yasuhiko Arakawa
    Abstract:

    A tunable optical notch filter was realized by thermally shifting the TM-like (the light's electric field perpendicular to the substrate) bandgap of a silicon photonic Crystal slab W1 Line-Defect waveguide with silica cladding. This device is compact-its footprint is 340times16 mum2, excluding the electrode pads. The 3-dB bandwidth of the device was about 5 nm, and the extinction ratio at the center wavelength was as high as 40 dB. A maximum center wavelength shift of 17.9 nm was attained at a heating power of 0.7W, with a tuning efficiency of 25.5 nm/W. The tuning response time was less than 100 mus

  • Optical add-drop multiplexer using PBG with hexagonal-hole lattice PC slab waveguides
    Optomechatronic Micro Nano Devices and Components, 2005
    Co-Authors: Akiko Gomyo, Hirohito Yamada, Tao Chu, Satomi Ishida, Jun Ushida, Yasuhiko Arakawa
    Abstract:

    We report on a channel-drop filter (CDF) with a mode gap of propagating mode for a photonic Crystal slab that was fabricated on silicon on an insulator wafer. The results simulated with 3-dimensional finite-difference time-domain and plane-wave methods demonstrated that an index-guiding mode for a Line Defect waveguide of a photonic Crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector for the propagating light-wave through the Line Defect waveguide, and it can be used as an optical filter. The filter bandwidth was varied from 1 - 8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550 - 1600 nm. We fabricated a Bragg reflector with a photonic Crystal Line-Defect waveguide and with Si-channel waveguides and obtained results of transmittance abrupt dips that come from the Bragg reflector that were measured in the transmittance spectrum. The experimental results are consistent with our theoretical analysis.