Polarization dynamics in vertical-cavity surface-emitting lasers with optical feedback: experiment and model

Abstract

Experiments and their interpretation on polarization dynamics and polarization switching in vertical-cavity surface-emitting lasers operated in the fundamental transverse mode regime are reviewed. Important observations are switching events to a mode with the lower unsaturated gain and the existence of elliptically polarized dynamical transition states after the destabilization of the low-frequency polarization mode. The observations demonstrate the need to consider explicitly the phase properties of the optical field as well as nonlinear effects affecting polarization selection above threshold. Good qualitative agreement is found with a model which takes into account the spin degrees of freedom of the light field as well as of the carriers ('spin-flip model'), if the spin-flip rate is taken to be some tens of 10 9 s −1. This constitutes a strong-though indirect-indication that spin dependent processes are important in polarization selection in the devices investigated.

Different regimes of low-frequency fluctuations in vertical-cavity surface-emitting lasers

“…25 As a first conclusion, multiple feedback-delay terms are not responsible for the type II LFF reported experimentally in Ref. 21. As we demonstrate below in Section 4, whether the VCSEL operates with type I or type II LFF is mainly dependent on the linear cavity anisotropies.…”

“…(1)- (4) consists in the inclusion of a self-gainsaturation coefficient in the model of Ref. 21. Our numerical study indicates that the gain-saturation coefficient increases the damping of the fast pulsating dynamics that underlie the slow LFF time traces (see Section 5), but is not responsible for the determination of the type of LFF dynamics.…”

“…21 and Eqs. (1)- (4) consists in the inclusion of a self-gainsaturation coefficient in the model of Ref.…”

Cavity Solitons in VCSEL Devices

“…This is also true in broad-area devices [122], while the situation may be more complex for highly divergent modes in even larger devices [123]. In VCSELs with cylindrical symmetry, optical injection [124] or feedback [125,126] can be employed to control the polarization of light. Since polarized optical injection or optical feedback can both induce bistability [127,128], all the necessary ingredients are available for CS formation in large-aperture devices.…”

Robust square-wave polarization switching in vertical-cavity surface-emitting lasers

“…When VCSELs are subject to optical feedback, the polarization stability is affected and polarization dynamics appear even in the case of perfectly isotropic feedback [17]. Polarizationrotated optical feedback-where the two linearly polarized components, LP-x and LP-y, of the light emitted by the device are fed back into the laser cavity after the LP-x component is converted into the LP-y component and vice versa-induces a regular polarization dynamics which can be as fast as 9 GHz [7,8].…”