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Register a new userOptical performance monitoring at 640Gb/s via slow-light in a silicon nanowire
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We demonstrate optical performance monitoring of in-band optical signal to noise ratio (OSNR) and residual dispersion, at bit rates of 40Gb/s, 160Gb/s and 640Gb/s, using slow-light enhanced optical third harmonic generation (THG) in a compact (80 micron) dispersion engineered 2D silicon photonic crystal waveguide. We show that there is no intrinsic degradation in the enhancement of the signal processing at 640 Gb/s relative to that at 40Gb/s, and that this device should operate well above 1Tb/s. This work represents a record 16-fold increase in processing speed for a silicon device, and opens the door for slow light to play a key role in ultra-high bandwidth telecommunications systems.
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Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.
We report the observations of spontaneous Raman scattering in silicon photonic crystal waveguides. Continuous-wave measurements of Stokes emission for both wavelength and power dependence is reported in single line-defect waveguides in hexagonal lattice photonic crystal silicon membranes. By utilizing the Bragg gap edge dispersion of the TM-like mode for pump enhancement and the TE-like fundamental mode-onset for Stokes enhancement, the Stokes emission was observed to increase by up to five times in the region of slow group velocity. The results show explicit nonlinear enhancement in a silicon photonic crystal slow-light waveguide device.
Hexagonally aligned, free-standing silicon nanowire (SiNW) arrays serve as photonic resonators which, as compared to a silicon (Si) thin film, do not only absorb more visible (VIS) and near-infrared (NIR) light, but also show an inherent photonic light concentration that enhances their performance as solar absorbers. Using numerical simulations we show, how light concentration is induced by high optical cross sections of the individual SiNWs but cannot be optimized independently of the SiNW array absorption. While an ideal spatial density exists, for which the SiNW array absorption for VIS and NIR wavelengths reaches a maximum, the spatial correlation of SiNWs in an array suppresses the formation of optical Mie modes responsible for light concentration. We show that different from SiNWs with straight sidewalls, arrays of inverted silicon nanocones (SiNCs) permit to avoid the mode suppression. In fact they give rise to an altered set of photonic modes which is induced by the spatial correlation of SiNCs in the array, and therefore show a higher degree of freedom to independently optimize light absorption and light concentration. Apart from explaining the good light absorbing and concentrating properties of SiNC arrays, the work justifies a revaluation of SiNW arrays as optical absorbers.
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals is theoretically studied. Using a scattering-matrix approach and the Wigner-Smith delay time concept, we show that optical absorbance benefits both from slow-light phenomena as well as a high filling factor of the energy residing in the liquid. Utilizing strongly dispersive photonic crystal structures, we numerically demonstrate how liquid-infiltrated photonic crystals facilitate enhanced light-matter interactions, by potentially up to an order of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized absorbance cells for optical detection in lab-on-a-chip systems.
We obtained exact solutions for the wave function and the Green function in the slow light pulse with the group velocity, consistent with the Fermi velocity in graphene.
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