Calibration of cascaded phase shifters using pairwise scan method in silicon photonics integrated chip

Cascaded phase shifters (CPSs) based on silicon photonics integrated chips play important roles in quantum information processing tasks. Owing to an increase in the scale of silicon photonics chips, the time required to calibrate various CPSs has increased. We propose a pairwise scan method for rapidly calibrating CPSs by introducing equivalent Mach Zehnder Interferometer structures and a reasonable constraint of the initial relative phase. The calibration can be nearly completed when the scanning process is finished, and only a little calculation is required. To achieve better performance, the key components, thermal optical phase shifter and 2 * 2 50/50 multimode interference coupler, were simulated and optimized to prevent thermal crosstalk and ensure a good balance. A 6-CPSs structure in a packaged silicon photonics chip under different temperature was used to verify the rapid pairwise scan method, and a fidelity of 99.97% was achieved.