Influence of coupling conditions on the time delay characteristics of parallel-cascaded optical waveguide ring resonators

The influence of coupling conditions of parallel-cascaded waveguide ring resonators on the time delay application in the optically phased array antennas is analyzed. Two kinds of coupling conditions, over-coupling and restriction free are considered to achieve a certain target delay time by parallel-cascaded three ring resonators. The results show that the restriction free coupling condition is better than the over-coupling one to obtain a flat time delay response in the target delay bandwidth especially for the small target delay time, which is the advantage of ring-resonator-based tunable true time delay line. The influence of round-trip loss on the time delay response and the transmission amplitude response is also investigated, which indicates that ring resonators with low optical round-trip loss are preferred to achieve a high performance true time delay line.