Waveguide-Based 1.5 µm Optical Isolator Based on Magneto-Optic Effect in Ferromagnetic MnAs

Abstract

We developed a 1.5-µm-band, transverse-magnetic-mode waveguide isolator based on the nonreciprocal-loss phenomenon. The device consists of an optical waveguide with an InGaAs/InGaAlAs multiple-quantum-well amplifier and a ferromagnetic MnAs layer attached to the waveguide. The combination of the optical waveguide and the magnetized MnAs layer produces a magneto-optic effect called the nonreciprocal loss–a phenomenon where the propagation loss of light is larger in backward than in forward propagation. We present the guiding principle of the design of the structure of the device. A prototype device with a MBE-grown epitaxial MnAs layer showed a nonreciprocity of 9.8 dB/mm at a wavelength of 1.54 µm. Our device can be monolithically integrated with waveguide-based optical devices on an InP substrate.