[Show abstract][Hide abstract] ABSTRACT: We show a direct comparison between silicon reconfigurable delay lines based on coupled resonator optical waveguides and photonic crystal waveguides. The structures are used to selectively delay the two orthogonally polarized channels of a RZ-PolDM-DQPSK format at 100 Gbit/s.
[Show abstract][Hide abstract] ABSTRACT: Coupled-ring resonator-based slow light structures are reported and discussed. By
combining the advantages of high index contrast silicon-on-insulator technology with
an efficient thermo-optical activation, they provide an on-chip solution with a
bandwidth of up to 100 GHz and a slowdown factor of up to 16, as well as a continuous
reconfiguration scheme and a fine tunability. The performance of these devices is
investigated in detail for both static and dynamic operation, in order to evaluate their
potential in optical signal processing applications at high bit rate. The main
impairments imposed by fabrication imperfections are also discussed in relation to the
slowdown factor. In particular, the analysis of the impact of backscatter, disorder
and two-photon absorption on the device transfer function reveals the ultimate
limits of these structures and provides valuable design rules for their optimization.
Full-text · Article · Sep 2010 · Journal of optics
[Show abstract][Hide abstract] ABSTRACT: Tunable coupled resonator optical waveguides (CROWs) are powerful and versatile devices that can be used to dynamically control the delay of optical data streams on chip. In this contribution we show that CROW delay lines fabricated on a silicon on insulator (SOI) platform are suitable for applications in the emerging scenario of optical systems at 100 Gbit/s. Issues concerning technology, design, limits and applications of SOI CROWs are discussed. The performances of silicon CROW delay lines activated by thermal tuning are compared to those of glass CROW in terms of power consumption, thermal crosstalk and reconfiguration speed. The continuous delay of 10-ps long optical pulses by 8 bit length is demonstrated by using a silicon CROW with a bandwidth of 87 GHz and made of 12 RRs. At 100 Gbit/s this structure provides comparable figures of merit (fractional delay of 0.75 bit/RR and fractional loss of 0.7 dB per bit-delay) of state-of-the art glass CROW operating at 10 Gbit/s, yet the area of the latter being three order of magnitude larger. The compatibility of silicon CROW with the emerging 100 Gbit/s systems is demonstrated by showing error-free phase-preserving propagation of a 100 Gbit/s return-to-zero (RZ) polarization-division-multiplexing (PolDM) differential quaternary phase shit keying (DQPSK) signal dynamically delayed by the CROW. It is also demonstrated that a silicon CROW can be used in a PolDM system to introduce a polarization selective delay in order to optimize the time interleaving of the two orthogonally polarized data streams.
No preview · Article · Apr 2010 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: We report the first (to our knowledge) experimental observation of resonant cavity-enhanced photosensitivity in As(2)S(3) chalcogenide glass film at 1550 nm telecommunication wavelength. The measured photosensitivity threshold is <0.1 GW/cm(2), and a photoinduced refractive index increase as large as 0.016 is observed. The photosensitive process is athermal; further, we confirm the absence of two-photon absorption in As(2)S(3), suggesting that defect absorption accounts for the energy transfer from photons to glass network. Besides its potential application for reconfigurable photonics circuit, such photosensitivity is also an important design consideration for nonlinear optical devices using chalcogenide glasses.
[Show abstract][Hide abstract] ABSTRACT: We report on the direct observation of backscattering induced by sidewall roughness in high-index-contrast optical waveguides based on total internal reflection. Our results demonstrate that backscattering is one of the most severe limiting factors in state-of-the art silicon on insulator nanowires employed in densely integrated photonics. We also derive the general relationship between backscattering and geometrical and optical parameters of the waveguide. Further, the role of roughness in polarization rotation and coupling with higher-order modes is pointed out.
Full-text · Article · Jan 2010 · Physical Review Letters
[Show abstract][Hide abstract] ABSTRACT: The potential of coupled resonator optical waveguides (CROWs) as integrated reconfigurable delay lines has been recently demonstrated in a glass-based device by continuously controlling the delay of optical data streams over several bit lengths. Although the exploitation of a medium index contrast glass waveguide leads to low insertion losses, allowing large absolute delays, it poses a hard limit on the maximum bandwidth of the device. The leap toward a high index contrast silicon platform is therefore mandatory for the processing of signals at high bit-rates (> 40 Gbit/s). The higher the bit rate, the lower is the required absolute delay (the fractional delay being equal) - this compensates for the higher losses of silicon waveguides while preserving the performance of the reconfigurable CROW in terms of storage efficiency and easy management of the delay. In this paper, the authors present a preliminary characterization of a reconfigurable CROW delay line realized in silicon-on-insulator (SOI) with thermooptic control of the delay.
[Show abstract][Hide abstract] ABSTRACT: The state-of-the-art of coupled resonator optical waveguides made of chains of ring resonators in glass and SOI platforms is reviewed. Issues concerning technology, design, limits and applications in the linear and nonlinear regime are discussed.
[Show abstract][Hide abstract] ABSTRACT: Cavity-enhanced photosensitivity of As2S3chalcogenide glass films is measured using planar micro-disk resonators. We observed infrared index trimming by 1550 nm wavelength light, cavity instability and confirmed the absence of two photon absorption.
[Show abstract][Hide abstract] ABSTRACT: Backscattering and its dependence on group index is experimentally studied in ring-resonators and photonic crystals. Independently of the structure, the behavior of optical devices can be dramatically modified as backscattered power increases with group index.
[Show abstract][Hide abstract] ABSTRACT: We demonstrated 6-THz wavelength conversion of a 10 Gbit/s DPSK signal via four-wave-mixing in a silicon coupled resonator optical waveguide. The device provides 16 dB enhancement of the conversion efficiency with negligible phase information distortion.
[Show abstract][Hide abstract] ABSTRACT: In ideal conditions the four wave mixing conversion efficiency is enhanced by the slowing down factor to the fourth power. We have investigated FWM. In ideal conditions the four wave mixing conversion efficiency is enhanced by the slowing down factor to the fourth power. We have investigated FWM in coupled resonator optical waveguides both numerically and experimentally this phenomena, also in presence of attenuation and chromatic dispersion.
[Show abstract][Hide abstract] ABSTRACT: We present a technological approach to the realization of channeled optical waveguides, starting from reactively sputtered tellurite glass thin films, grown on silica-coated 4" Si wafers. In particular, optical lithographic process and etching recipes have been developed to overcome the solubility of TeO(2) films in aqueous solutions, and to process them into high-index contrast structures with minimized post-etch roughness. Optical tests on preliminary rib waveguide geometries feature 6.3 dB/cm propagation loss for fundamental TE mode at lambda = 1.5 microm.
[Show abstract][Hide abstract] ABSTRACT: An endless polarization stabilization method is applied to a 40-Gbit/s RZ-DQPSK polarization-division multiplexed optical system. The effectivness of the polarization stabilizer in allowing the polarization demultiplexing of the two orthogonally polarized channels is experimentally verified.
[Show abstract][Hide abstract] ABSTRACT: Photoelastic tomography is exploited to investigate the effect of the spinning process on residual stress development in spun fibers. High-spatial-resolution measurements of stress profiles in spun and corresponding unspun fibers are compared. The resulting differences correspond to a reduction of the intrinsic linear birefringence as a consequence of an applied constant spinning.
No preview · Article · Jan 2005 · IEEE Photonics Technology Letters
[Show abstract][Hide abstract] ABSTRACT: By means of photoelastic tomography the effect of the spinning process on the development of residual stress in spun fibers is investigated. Measured stress distributions in spun and corresponding unspun fibers are compared.
[Show abstract][Hide abstract] ABSTRACT: By means of photoelastic tomography the effect of the spinning process on the development of residual stress in spun fibers is investigated. Measured stress distributions in spun and corresponding unspun fibers are compared