The Polarization Switching (PS) appearing in longwavelength vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonal optical injection is investigated theoretically and experimentally. We have studied the injected optical power required for PS as a function of the frequency detuning between the injected light and the orthogonal linear polarization of the VCSEL. For a wide range of bias currents applied to the device, the injected power required for the occurrence of PS exhibited a minimum and a plateau with respect to the frequency detuning. The minimum (plateau) was found at negative (positive) frequency detuning. The bistable behaviour of the polarization is described. Our experimental results confirm the theoretical predictions of M. Sciamanna et al, Phys Rev. A, vol. 73, 023811, 2006. The levels of the minimum and the plateau were observed to increase as higher bias currents were applied to the VCSEL. A first theoretical and experimental observation of the disappearance and further appearance of PS when increasing the injected power in long-wavelength VCSELs is described. This situation is obtained for small levels of negative frequency detuning and for large enough values of applied bias current. A good overall qualitative agreement is found between our theoretical and experimental results.

Abstract-We study numerically the transverse-mode dynamics of a vertical-cavity surface-emitting laser with external optical injection. We consider the case in which two transverse modes with parallel polarizations are exited. Varying the strength and frequency of the injected field, we find a rich variety of complex behaviors. We show that by increasing the optical injection strength the laser does not turn into a single-mode laser, as would be expected if the transverse modes have perpendicular polarizations.

Abstract-We study the dynamics of a vertical-cavity surfaceemitting laser with continuous-wave orthogonal optical injection from a tunable laser. We use the dynamical properties of polarization bistability and the interplay with internal or external noise to demonstrate numerically a reliable logic output to two logic inputs encoded in the optical frequency of the injected light. This all-optical configuration is more than ten times faster than the electro-optical implementation and has the advantage of operating at constant injection power.

The transverse mode selection induced by optical injection in a VCSEL emitting in two transverse modes is analyzed from a theoretical point of view. Different pairs of transverse modes with parallel or orthogonal polarizations are considered. In general, we show that transverse mode selection can be achieved when the two modes have parallel or orthogonal polarizations. The selection is not possible only when both modes have parallel polarizations and the mode with the lowest threshold current has a lower injection rate than the other mode. Different forms of the selection region in the injected powerinjection current plane appear depending on the polarization of the transverse modes. When both transverse modes are orthogonally polarized the mode with the lowest threshold is selected when the injected power surpasses a value that depends on the injection current. However when both modes have parallel polarizations the selection region has a completely different shape because the selection of the mode is no longer possible if the injected power or the injected current are large enough. We also show that the modal selection is favoured as the frequency of the injected light becomes smaller than the frequency of the mode to be selected.

Sustained, large amplitude and tuneable birefringenceinduced oscillations are obtained in a spin-Vertical Cavity Surface Emitting Laser (spin-VCSEL). Experimental evidence is provided using a spin-VCSEL operating at 1300 nm, under continuous wave optical pumping and at room temperature. Numerical and stability analyses are performed to interpret the experiments and to identify the combined effects of pump ellipticity, spin relaxation rate and cavity birefringence. Importantly, the frequency of the induced oscillations is determined by the device's birefringence rate which can be tuned to very large values. This opens the path for ultrafast spin-lasers operating at record frequencies exceeding those possible in traditional semiconductor lasers and with ample expected impact in disparate disciplines (e.g. datacomms, spectroscopy).

We study the transverse-mode dynamics of vertical-cavity surface-emitting lasers with weak optical feedback. We use a model that takes into account the spatial dependence of the transverse modes and of two carrier density profiles, associated with confined carriers in the quantum well region of the laser and unconfined carriers in the barrier region. Optical feedback is included as in the Lang-Kobayashi model. We find that for adequate parameter values antiphase dynamics occurs. As the injection current varies, the antiphase dynamics is destroyed through a sequence of periodic mixed states leading to in-phase dynamics. In these mixed states there are time intervals in which the modes are in phase, followed by time intervals in which they are in antiphase. We study the origin of the antiphase dynamics, assessing the role of the different spatial profiles. We show that the competition between the different profiles leads to the observed antiphase behavior.

We analyze the influence of thermal effects on the polarization-resolved light-current (LI) characteristics of verticalcavity surface-emitting lasers (VCSELs). We use a model that is an extension of the spin-flip model incorporating material gain that is frequency and temperature dependent, and a rate equation for the temperature of the active region, which takes into account decay to a fixed substrate temperature, Joule heating and nonradiative recombination heating. The model also incorporates the red shift for increasing temperature of the gain curve and of the cavity resonance. The temperature sensitivity of the lasing threshold current is found to be in good qualitative agreement with observations and with previous reports based on detailed microscopic models. The temperature dependence of the polarization switching point, when the dominant polarization turn off and the orthogonal polarization emerges, is characterized in terms of various model parameters, such as the room-temperature gain-cavity offset, the subtracte temperature, and the size of the active region.

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