Polarization insensitive optical amplifier consisting of two semiconductor laser amplifiers and a polarization insensitive isolator in series

A polarization-insensitive optical amplifier consisting of two semiconductor laser amplifiers and a polarization-insensitive isolator in series is presented. The isolator not only eliminates the cavity coupling between two amplifiers, but also rotates polarized forward light by 90 degrees . Experiments demonstrate the elimination of cavity coupling and a polarization sensitivity of 0.6 dB with a gain of 26 dB.