Widely Tunable Photonic Filter Based on Equivalent Chirped Four-Phase-Shifted Sampled Bragg Gratings

TL;DR

This paper presents a silicon photonic dual-band filter with wide tunability based on equivalent chirped four-phase-shifted Bragg gratings, enabling adjustable frequency division for advanced optical communication applications.

Contribution

It introduces a novel integrated dual-band photonic filter utilizing equivalent chirped 4PS-SBG on SOI, with wide-range tunability achieved via thermo-optic effects and micro-heaters.

Findings

Achieved continuous tuning of passband interval from 52.1 GHz to 439.5 GHz.

Demonstrated stable dual-band operation at 100 GHz, 200 GHz, 300 GHz, and 400 GHz.

Utilized a semiconductor mode-locked laser as the light source for frequency division.

Abstract

We have developed an integrated dual-band photonic filter (PF) utilizing equivalent chirped four-phase-shifted sidewall-sampled Bragg gratings (4PS-SBG) on a silicon-on-insulator (SOI) platform. Using the reconstruction equivalent-chirp technique, we designed linearly chirped 4PS Bragg gratings with two {\pi}-phase shifts ({\pi}-PS) positioned at 1/3 and 2/3 of the grating cavity, introducing two passbands in the +1st order channel. Leveraging the significant thermo-optic effect of silicon, dual-band tuning is achieved through integrated micro-heaters (MHs) on the chip surface. By varying the injection currents from 0 to 85 mA into the MHs, the device demonstrates continuous and wide-range optical frequency division (OFD) performance, with the frequency interval between the two passbands adjustable from 52.1 GHz to 439.5 GHz. Four notable frequency division setups at 100 GHz, 200 GHz, 300 GHz, and 400 GHz were demonstrated using a 100 GHz, 1535 nm semiconductor passive mode-locked laser as the light source.