1.3-μm polarization insensitive amplifiers with integrated-mode transformers

We report for the first time polarization-insensitive, mixed-strain quantum-well semiconductor optical amplifiers (QW SOAs) with monolithically integrated laterally tapered section for mode transformation. This taper section improves coupling efficiency to cleaved single-mode fibers by 3-4 dB compared to an untapered linear waveguide. We have demonstrated 18 dB chip gain with less that 1-dB polarization sensitivity of the gain. We also found that the output saturation power is about 10 dBm for all polarizations. The gain bandwidth was estimated to be 45 nm.