1.3-mu m polarization insensitive amplifiers with integrated-mode transformers

We report for the first time polarization-insensitive, mixed-strain quantum-well semiconductor optical amplifiers (QW SOA's) 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 l-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 15 nm.