Tuning Optimization of Ring Resonator Delays for Integrated Optical Beam Forming Networks

Comprehensive tuning optimization of an integrated optical ring resonator (ORR) based 1 × 4 optical beam forming network (OBFN) for W-band millimeter wave (mmW) phased arrays is reported. The OBFN chip is implemented using a ultralow loss silicon nitride technology and a two stage binary tree topology. The delay responses of a singleand multiORR delay line were carefully measured, and the results agree well with a lossless theoretical model. Tuning of an ORR was calibrated and verification experiments were performed to verify the tuning accuracy. A flattened delay response for a 3-ORR delay line was achieved, demonstrating a bandwidth of 6 GHz and dynamic tuning range of 209 ps, which corresponds to a phase shift of 33.4π for an 80-GHz signal. A larger bandwidth can be achieved by reducing the dynamic tuning range. The result is promising for high data rate mmW communications with beamforming.