Exploring lasing modes and polarization characteristics in broad-area square-shaped vertical-cavity surface emitting lasers with frequency detuning

We experimentally explore the polarization characteristics of broad-area square-shaped vertical-cavity surface emitting lasers with the cryogenic cooling to achieve a wide range of frequency detuning. At room temperature the lasing modes are subject to thermal effects and exhibit the phenomenon of polarization switching. For operating temperatures below 260 K, the transverse modes are confirmed to be mainly controlled by the lateral oxide boundary and usually do not display polarization switching. Near the maximum frequency detuning, the lasing modes are well localized on the ray trajectories and display a remarkable frequency-locking phenomenon from single-frequency to multi-frequency operation for the injected current changing from near to far above lasing threshold. (letter)