Polarization-Resolved Modulation Response of Single-Transverse-Mode Vertical-Cavity Surface-Emitting Lasers

The small-signal modulation response of vertical-cavity surface-emitting lasers (VCSELs) is studied numerically, based on the spin-flip model. A detailed characterization of the influence of various parameters, such as the dichroism, the birefringence, the spin-flip rate and the noise level is done. The analysis is performed in regions of the parameter space where the operating conditions, in the absence of modulation, are such that there is either stable single linear polarization, or bistability of two orthogonal linear polarizations or polarization instability. In the instability region the intensities of the orthogonal polarizations display anticorrelated self-sustained oscillations that result in a complex small-signal modulation response, exhibiting multiple resonance peaks with frequencies that vary with the injection current and the spin-flip rate. In contrast, in parameter regions where there is stable single polarization the modulation response of the total intensity is as that of a single-mode laser, exhibiting a conventional single-resonance peak, and is almost not influenced by the value of the spin-flip rate. Polarization mode-hopping results in a distortion of the polarization-resolved modulation response at low frequencies.