Polarization switching in a long-wavelength vertical-cavity surface-emitting laser (VCSEL) under parallel optical injection is analyzed in a theoretical and experimental way. For the first time, to our knowledge, we report experimentally a state in which injection locking of the parallel polarization and excitation of the free-running orthogonal polarization of the VCSEL are simultaneously obtained. We obtain very simple analytical expressions that describe both linear polarizations. We show that the power of both linear polarizations depend linearly on the injected power in such a way that the total power emitted by the VCSEL is constant. We perform a linear stability analysis of this solution to characterize the region of parameters in which it can be observed. Our measurements qualitatively confirm the previous theoretical predictions.

We present experiments and numerical simulations of optical frequency combs generated by gain-switching a single mode laser diode when subject to optical injection. Our analysis focuses on the combs with a frequency separation $f_R$ in the GHz range. We present experimental maps in the parameter space spanned by the detuning and the strength of the optical injection that identify the boundaries between regions with different dynamical states. A rich variety of nonlinear behaviors including injection-locked, unlocked and irregular combs are observed and analyzed. The dynamical state corresponding to an injection locked comb, PN, is characterized by an optical phase oscillation with a well defined amplitude in such a way that repeats or changes in 2 with an $N/f_R$ period, where N is a natural number. Different regions of locked combs with a tongue shape around detuning values given by multiples of $f_R$ appear in the maps. P1 and P2 are the most widespread locked states for large values of the modulation amplitude. As this amplitude decreases a much larger variety of PN states with large values of N appear in small area regions of the map. Our numerical simulations are in very good agreement with experimental results.

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 (OFC) 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.

A first experimental observation of three different types of frequency-induced polarization bistabilities in 1550-nm single transverse and polarization mode vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonal optical injection is described. The hysteresis width of the bistable region that appears at longer wavelegth detunings increases as the injected power or the VCSEL current increases. Very large hysteresis widths are obtained. These widths are more than seven times larger than previously reported widths.

In this paper, we report a theoretical and experimental study of the phase diffusion in a gain-switched single-mode semiconductor laser. Our modelling includes nonlinear dependencies of the carrier recombination rate and the semiconductor material gain on the carrier number. Also a comparison with the results obtained with linear models is performed. We focus on the below threshold operation, that is, the regime where most of the phase diffusion occurs in quantum random number generators based on the above mentioned system. Using the extracted parameters for our laser and simple analytical expressions for the laser linewidth, we show that logarithmic material gain and cubic carrier recombination dependence on the carrier number must be considered for a good agreement between experiments and theory. In this way we show that consideration of these nonlinearities is essential for obtaining a good quantitative description of the phase diffusion when using rate equations modelling.