Tunable Optical Delay Line Based on SOI Contradirectional Couplers with Sidewall-Rnodulated Bragg Gratings

Abstract

Tunable delay line is one of the key components in optical communication and microwave system. We propose and demonstrate tunable optical delay line based on silicon-on-insulator (SOI) contradirectional couplers with sidewall-modulated Bragg gratings. Compared to the similar scheme based on Bragg gratings, the design complexity and fabrication process of the proposed scheme is simplified. After optimization, tunable group delay line of 50 ps within the bandwidth of 12 nm is realized with grating length of 1.8 mm, and the apodized Bragg gratings show better uniformity. Finally, we combine the proposed scheme with an ultra-compact reflector for doubling group delay, and the fabricated 6-mm device can achieve large group delay of 400 ps within bandwidth of 12 nm.