Electrically tuned fractional-order temporal differentiator in silicon photonics

Abstract

Here, full-wave analysis and design of an electrically tunable optical fractional-order temporal differentiator (DIFF) based on an ultra-compact microring resonator (MRR) has been presented. Electrical tunability has been realized through free carrier dispersion (FCD) effect in the resonator with P-I-N and P-N junctions. The first-order optical DIFF is realized based on the critically-coupled resonator without applying any bias voltages in the junctions. Also, fractional-order DIFF with differentiation order α > 1 is realized by over-coupled resonator with the forward-biased P-I-N and P-N junctions. While, fractional-order DIFF with α < 1 is realized by under-coupled resonator with reverse-biased P-N junction. The high performance of the designed tunable optical DIFFs and their high accuracy have been confirmed considering an ultra-fast Gaussian input pulse with short full-width at half-maximum (FWHM) of 6.3 ps.