Polarization-Independent Magneto-Optical Waveguide Isolator Using TM-Mode Nonreciprocal Phase Shift

A polarization-independent magneto-optical waveguide isolator using nonreciprocal phase shift for a TM mode is proposed. The isolator is a Mach-Zehnder interferometer (MZI) that is composed of transverse electric (TE)-transverse magnetic (TM) polarization converters and nonreciprocal phase shifters. The MZI induces a phase difference between the reciprocal TE and nonreciprocal TM modes that are converted to each other by the polarization converter. Since the design uses a nonreciprocal phase shift only for the TM mode, it allows fabrication of an integrated structure. This paper describes the principle of operation and its design.