A Polarization Insensitive Semiconductor Optical Amplifier

This letter proposes an integrated InGaAsP-InP/silicon-on-insulator (SOI) polarization insensitive semiconductor optical amplifier (SOA). The SOA consists of an SOI waveguide-based polarization diversity circuit and an InGaAsP-InP gain block. Input light with arbitrary linear polarization state will pass through the gain block twice for a roundtrip with mutually orthogonal polarization state in its forward and backward path, respectively. As such, the polarization-dependent gain (PDG) is effectively reduced. Since the returning path is not spatially overlapped with the forward path, no extra circulator is needed and the device still has two separate ports, one for input and one for output. Simulation results show that the PDG is negligibly small and the device has a broad working band of 60 nm for a PDG below 0.5 dB. This design is compatible with the mature semiconductor fabrication technology and can be monolithically integrated with other optical components.