Semiconductor Optical Amplifiers (SOAs) are of central interest as multifunctional, easy-to-integrate components for the development of future optoelectronic systems. Their dependence upon the incoming light polarization is a well-known, but still debated, issue in the context of emerging optical telecommunication networks, fueling the need for a detailed polarimetric characterization of such structures.
In this paper, we present what we believe to be the first systematic polarimetric analysis within the frame of the Mueller-Stokes formalism of an integrated InP/InGaAsP SOA around 1550 nm. The challenge stems from the amplifying, active, spectrally broadband and nonlinear nature of the component. For the sake of our study, we have developed a highly sensitive, free-space, polarimetric set-up, with the additional experimental challenge induced by the spatial constraints of a guided-wave device, most notably in terms of light injection. Physical phenomena (intrinsic noise contribution of internal sources, carrier saturation due in particular to Amplified Spontaneous Emission, modal birefringence for index and gain...) responsible for the polarization dependence of the amplification process are identified, and discussion of the data highlights the need for an extended matrix formalism taking explicitly internal sources into account.