Novel nonmagnetic 30-dB traveling-wave single-sideband optical isolator integrated in III/V material

Various attempts have been made to fabricate waveguide-type isolators in III/N material by implanting magnetic materials, but none of them has so far resulted in a commercial product. Here, we report for first time on an integrated optical isolator implemented in III/V material. It consists of a single-sideband electrooptic modulator where traveling electrical waves make the transmission direction-dependent. Isolation is 30 dB, excess insertion loss is 8 dB. Residual rms ripple is 7% for peak-to-peak RF driving amplitudes of 3.5 V at 4.0 GHz. The estimated transmission penalty for 40 Gb/s return-to-zero differential phase shift keying (RZ-DPSK) signals is 0.2 dB (0 dB measured).