A Stokes-based spectro-polarimetric analysis of the amplified spontaneous emission in a semiconductor optical amplifier

Abstract

Semiconductor Optical Amplifiers (SOAs), key devices for future all-optical communication systems, are inherently polarisation-dependent, which is a major drawback for most networks applications. In spite of numerous studies carried out in order to design polarisation-insensitive structures, no complete spectro-polarimetric characterization of a SOA has been published so far. In particular, the spectral and polarimetric behaviour of the Amplified Spontaneous Emission (ASE), acting as a partly polarized broadband source, is of interest, since ASE draws from the same carrier reservoir as the amplified signal. In this paper, we present a full spectro-polarimetric characterization of ASE emitted from a commercial, strained-bulk SOA within the frame of the Stokes formalism. This formalism not only allows a determination of the degree of polarisation (DOP) of ASE directly from its Stokes vector, but also gives access to a full, spectrally resolved characterization of its polarized fraction with respect to the bias current applied to the SOA. The way the state of polarisation of that fraction is governed by the dependence of the material gain upon polarisation is spectrally resolved, quantified, and discussed. The same study is performed when a polarized signal is injected into the SOA.

© The Authors. All rights reserved. [DOI: 10.2971/jeos.2007.07025]