Robust square-wave polarization switching in vertical-cavity surface-emitting lasers (original) (raw)
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Journal of the Optical Society of America B, 2007
We study experimentally and numerically the influence of orthogonal optical feedback on the polarizationresolved light versus bias current characteristic (L-I curve) of vertical-cavity surface-emitting lasers (VC-SELs). The feedback scheme is such that only one linear polarization is selected to be fed back into the laser while the orthogonal polarization is completely suppressed before the output is rotated 90°and reinjected into the laser. We experimentally demonstrate that weak feedback levels modify the polarization switching point only slightly, but as the feedback increases the otherwise depressed mode grows and the hysteresis is suppressed. While polarization-preserved and X-orthogonal feedback have similar effects (X indicates the direction of the polarization selected at threshold), Y-orthogonal feedback strongly modifies the shape of the L-I curve, even suppressing the polarization-switching for strong enough feedback. Numerical simulations of the spin-flip model show good qualitative agreement with the observations. We also analyze the influence of various parameters, such as linear birefringence, dichroism, and the spin-flip relaxation rate.
Physical Review A, 2012
We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarizationrotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.
Journal of the Optical Society of America B, 1999
Experiments are described that show that polarization of light in a vertical-cavity surface-emitting laser subjected to isotropic optical feedback can jump regularly back and forth between two orthogonal states when the injection current is increased. The polarization-resolved light-current characteristic curves are thus channeled. This effect occurs when the dichroism of the laser is weak enough to allow the effective (isotropic) reflectance to impose the polarization. A comparison of a model introduced by San Miguel et al. [Phys. Rev. A 52, 1728] and the standard equations indicates that the best description is given when no spin relaxation is included.
Optical feedback induces polarization mode hopping in vertical-cavity surface-emitting lasers
Optics Letters, 2003
Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the linearly polarized intensities at the external-cavity frequency. The study of a simple stochastic delay differential equation suggests that these oscillations generated by the delay are typical of any hopping phenomenon between states.
2010
The hysteresis properties in bistable polarization switching (PS) of vertical-cavity surface-emitting lasers (VC-SELs) induced by variable-polarization optical feedback (VPOF) are investigated numerically. We mainly concentrate on the influence of sweep rate of the polarizer angle on the bistable PS for the cases with different feedback strengths and feedback delays. The output in the time domain and the representation on the Poincaré sphere plot are further presented to describe the two PS processes. The results show that the size of the hysteresis cycle of the PS follows a power-law relationship versus the sweep rate of the polarizer angle, and the feedback strength and feedback delay can modify the hysteresis properties significantly. A larger feedback strength leads to a narrower hysteresis loop, while a larger feedback delay gives rise to a wider hysteresis loop. Therefore the VPOF provides a new method for obtaining the controllable bistable PS in VCSELs, which is potentially interesting for applications that require polarization-bistable VCSELs.
Journal of The Optical Society of America B-optical Physics, 1999
We study the polarization-resolved dynamics of a vertical-cavity surface-emitting laser with mode-matched and polarization-preserving optical feedback. The total power can display low-frequency fluctuations, which are associated with drops in power of the dominant linearly polarized mode and with bursts of power of the depressed mode. However, for most parameter values the vertical-cavity surface-emitting laser output does not display low-frequency fluctuations, although antiphase dynamics between the two linear polarization components has been found. A theoretical model that includes all reflections in the external cavity with a minimum computational cost is developed.
Applied Physics Letters, 2007
The authors present experimental results showing that polarization selective optical feedback from an extremely short external cavity induces switching between the two fundamental transverse modes with orthogonal linear polarization of the otherwise ͑without optical feedback͒ polarization stable vertical cavity surface emitting laser. Moreover, when properly selecting the external cavity length within a subwavelength range the polarization state of the emitted light can be chosen in either of the two fundamental transverse modes and stabilized against injection current variations. The numerical results reported are in good agreement with experiments.