Polarization Dynamics in VCSEL-Based Gain Switching Optical Frequency Combs

In this paper, we report on the polarization dynamics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) under gain switching regime. We focus our analysis on the resulting optical frequency combs associated with the main and suppressed polarization modes. Measurement of the parameters characterizing the polarization behavior of our single-transverse mode VCSEL is performed from the analysis of high-resolution optical spectra. An extension of the spin-flip rate model to include nonlinear carrier recombination is developed. An analysis of polarization-resolved dynamics is performed by using the previous model with the measured VCSEL parameters. We show that two orthogonally polarized combs are generated that combine to produce a wider overall optical comb. We analyze the dependence of combs on the amplitude and frequency of the modulation. Our results are in agreement with experiments reported by Prior et al. We also analyze the dependence of the combs on the linear dichroism of the VCSEL We show that the change of this dichroism results in bistability between the two orthogonally polarized combs.