Silicon-integrated 6-bit tunable optical true-time delay line based on high-extinction-ratio electro-optic Mach-Zehnder switches

This study proposes and demonstrates a silicon-integrated 6-bit tunable optical true-time delay line (OTTDL) based on high-extinction-ratio (ER) electro-optic (EO) switches with fast tuning speed. Each switch is composed of a push-pull PIN-based Mach-Zehnder interferometer (MZI) switch structure with a tunable coupler to balance interference, which enhances the ER to >34 dB. The delay line features a delay step resolution of 5 ps and a maximum delay of 315 ps. The delay ripple of the OTTDL is suppressed to below 0.8 ps over a broad bandwidth of 10-43.5 GHz. With adequate switch ER, signal leakage suppression is achieved without activating variable optical attenuators (VOA), lowering the total power consumption to 166 mW.