Analysis of polarization independent Mach-Zehnder-type integrated optical isolator

This paper proposes, for the first time, an integrated optical isolator ind ependent of light polarization. A Mach-Zehnder interferometer (MZI) with tw o nonreciprocal phase shifters, one for transverse electric (TE) modes and another one for transverse magnetic (TM) modes can be adjusted so that it b locks the fundamental modes of the waveguides constituting the interferomet er propagating in one direction and is transparent for the modes propagatin g in the opposite direction. If the interferometer branch waveguides are in single mode regime, the performance of the device will not depend on the p olarization of incoming light. The nonreciprocal phase shifters can be real ized on structures with magnetization tangential to the propagation directi on. Three geometries of nonreciprocal phase shifters are discussed and tole rances are estimated.