High-contrast and low-power all-optical switch using Fano resonance based on a silicon nanobeam cavity

We experimentally demonstrate an ultra-compact all-optical switch involving Fano resonance based on a side-coupled Fabry-Perot (F-P) resonator and a silicon photonic crystal (PhC) nanobeam cavity, with an area of only 11 mu m(2). By optimizing the structure of the nanobeam cavity to increase its intrinsic quality factor (Q), we achieve a sharp asymmetric transmission spectrum, with an extinction ratio (ER) as high as 40 dB and a peak loss as low as 0.6 dB. As far as we know, this is the highest measured ER in PhC-based Fano resonance. These excellent properties enable us to realize an all-optical switch with shorter switching recovery time, lower power consumption, and higher contrast, compared to that involving Lorentzian resonance. For example, under signal trains of 2.5 Gb/s, switching energy with a contrast of 3 dB for the Fano case is 113 fJ, which is 8 dB smaller than that for the Lorentzian case. Furthermore, by performing blue-detuned filtering on the 15-Gb/s output signal light, the switching contrast of the all-optical switch based on Fano resonance is significantly improved from 0.67 dB to 9.53 dB. (c) 2018 Optical Society of America