High-power isolator for the 10-μm region employing interband Faraday rotation in germanium

Abstract

Interband Faraday rotation in intrinsic germanium has been employed to construct a room-temperature optical isolator for use in the intermediate infrared region. The device was tested at 9.55- and 10.59-μm wavelengths, and exhibited an isolation level of 41 dB at 106 W cm−2. The rotation is shown to be relatively insensitive to temperature at the two wavelengths and linear in magnetic field intensity up to 83 kG. The isolator figure of merit is about 60 deg per dB attenuation.