Experimental analysis of polarization dependence of ultrafast gain dynamics in SOAs

Abstract

Nonlinear polarization rotation in semiconductor optical amplifiers has been the focus of a lot of work in the past decade. A lot of research has been devoted to this phenomenon due to its possible use in all-optical switching. It has been mentioned as a possible competitor to such established switching techniques as cross-gain modulation, cross-phase modulation and four-wave mixing. The speed at which the switching can be performed is determined by the gain dynamics in the device. So far the majority of the work has focused on switching due to the relatively slow carrier density recombination, which limits the switching to the order of tens of gigahertz. If the polarization dependence of ultrafast gain mechanisms such as carrier heating and spectral hole burning can be identified and measured then there is the possibility to increase the switching speed obtainable using this process into the terahertz range. In order to further the understanding of the polarization dependence of the gain of a bulk SOA under tensile strain and to determine the plausibility of ultrafast all-optical switching using nonlinear polarization rotation an experiment is presented based on a four-wave mixing technique.