Demonstration of Interferometric Waveguide Optical Isolator with a Unidirectional Magnetic Field

A waveguide optical isolator employing a nonreciprocal phase shift is composed of a Mach–Zehnder interferometer incorporating a nonreciprocal phase shifter together with a reciprocal phase shifter. A conventional nonreciprocal phase shift isolator requires antiparallel magnetic fields. In this study, an optical isolator that operates with a unidirectional magnetic field is fabricated and its performance is demonstrated with an isolation ratio of 15.3 dB at a wavelength of 1559 nm. The isolator has two different waveguides in interferometer arms for obtaining different nonreciprocal phase shifts between two waveguides.