Analysis of nonlinear polarization rotation by an ultrashort optical pump and probe pulse in a strained semiconductor optical amplifier

Abstract

In this paper, a comprehensive dynamic model is used to study the nonlinear polarization rotation (NPR) of a probe signal in the presence of a copropagating pump signal in a strained semiconductor optical amplifier (SOA). Pump and probe signals are Gaussian pulse with 200 fs pulse width, propagating in a 500 μm SOA. In the present model, the effects of carrier dynamics on the SOA gain and phase are considered and the NPR of the probe signal is measured by the ellipticity angle using the Stokes vector and Mueller matrices. The effects of several important factors on the NPR of the probe signal are investigated. These factors include pump signal energy, free carrier absorption and two-photon-absorption nonlinear effects, tensile/compressive strain, pump-probe pulse width, and pump-probe delay time. The results show that the pulse width and strain have a considerable effect on the ellipticity angle deviation (EAD); we especially see that the tensile strain increases the EAD, and the compressive strain reduces the EAD compared to the no strain structure. For a specific range of pulse width (here 0.2 ps to 1 ps), the EAD increases noticeably with the pulse width. It is also shown that, for the pump-probe delay time, the maximum EAD is obtained when the delay time is 0.1 ps.