Programmable Coupler Ladder Based on Lithium Niobate Y-Junction Reflector

This paper presents a proposal for a novel integrated tun-able coupler device called programmable coupler ladder, based on Titanium diffused lithium niobate waveguide and Y-junction reflector. Unlike the traditional serial to parallel converter, the coupler ladder sorts the output bits in the time axis using a built-in delay waveguide. With a proper control signal it can perform signal processing at the bit level. It also can generate coherent multi-channel outputs with theoretically arbitrary amplitude and phase from continuous input light source. Its application in optical microwave beam forming is briefly described. The key component, built-in delay line based on Y-junction reflector, has been experimentally verified via a loop resonator structure. 1 dB loss is found for each Y-junction reflector , which enables a practicai coupler ladder. The loop itself is also an important device for optical signal processing.