Analysis of a semiconductor optical amplifier with polarization-insensitive gain and polarization-insensitive phase modulation

The polarization dependence of phase modulation in a semiconductor optical amplifier (SOA) has negative impacts on some pump/probe applications of SOAs. We propose the necessity of fabricating SOA with polarization-insensitive gain and polarization-insensitive phase modulation and study the possibility. The investigation reveals that polarization sensitivity of phase modulation depends on the product of an optical confinement factor and a material differential refractive index. We study strain effects on polarization dependences of the differential refractive index and gain in a strained multiple-quantum well; the results demonstrate that by conducting the proper design of an active region and waveguide structure, reduction of SOA polarization sensitivity to gain and phase modulation can be achieved. An optimally designed example of a 1.55 µm tensile-strained MQW SOA is given.