Engineering the nonlinear phase shift using multistage autoregressive moving-average optical filters

摘要

In this paper, we propose and demonstrate the application of concepts from digital filter design to optimize artificial optical resonant structures to produce a nearly ideal nonlinear phase shift response. Multi-stage autoregressive moving average (ARMA) optical filters (ring resonator based Mach-Zehnder interferometer lattices) are designed and studied. The filter group delay is used as an alternate measure instead of finesse or quality factor to study the nonlinear sensitivity for multiple resonances. The nonlinearity of a 4-stage ARMA filter is 17 times higher than that of the intrinsic material. We demonstrate that the nonlinear sensitivity can be increased within the same bandwidth by allocating more in-band phase or using higher-order filter structures and that the nonlinear enhancement improves with increasing group delay. We also investigate some possible ways to pre-compensate the nonlinear response to reduce the occurrence of optical bistabilities. The impact of optical loss, including linear absorption and two-photon absorption, and fabrication tolerance are discussed in post-analysis.