Waveguide polarization-independent optical circulator

We fabricated a new type of waveguide polarization-independent optical circ ulator which does not need a polarization-beam splitter. The circulator is based on a nonreciprocal Mach-Zehnder interferometer which consists of two waveguide Faraday rotators, two thin-film half-waveplates and two planar li ghtwave circuit-type 3-dB couplers. The fabricated circulator provides a 14 .0-23.7-dB isolation and a 3.0-3.3 dB insertion loss at lambda = 1.55 mu m. This circulator presents a new possibility for developing nonreciprocal de vices in the field of integrated optics.