Evanescent Semiconductor Active Optical Isolators for Low Insertion Loss and High Gain Saturation Power

We have designed evanescent semiconductor active optical isolators to realize lower forward transparent current in transverse electric (TE) mode integrable semiconductor active optical isolators with 9.3 dB/mm optical isolation. Evanescent semiconductor active optical isolators are composed of a semiconductor optical amplifier waveguide with an InGaAsP waveguide layers having an Fe layer at its sidewall upon an MQW active layer, allowing TE-mode optical isolation to be realized without etching the MQW active layer unlike conventional TE-mode semiconductor active optical isolators. Evanescent-mode optical isolators enable higher internal quantum efficiency and lower transparent current, compared with conventional TE-mode optical isolators. Furthermore, it was found that the evanescent-mode optical isolators had higher 3 dB saturation output power.