A New Structural Design that Optimizes the Polarization and Mode Characteristics of Vertical Cavity Surface Emission Lasers

The spectrum of the vertical-cavity surface-emitting lasers (VCSELs) used in chip-scale atomic clocks must satisfy strict requirements. As for the common oxide-confined VCSEL, the confining range for the light field in the transverse direction depends on the thickness and aperture of the oxide layer. By optimizing the thickness, number of layers, and aperture of the oxide layer, the lasing of higher-order transverse modes can be reduced. The instability of the polarization of VCSELs has been a concern since their successful development, and this characteristic can be improved by introducing non-uniform losses or small strains. Based on the current application status, this paper proposes a new structure design, where the laser electrodes have an asymmetric structure and a quasi-circular ring pattern is etched near the oxide hole at the top of the laser. During the operation, non-uniform current is introduced into the laser, and the loss of high-order transverse modes is increased. In this way, the polarization and mode characteristics of VCSELs are optimized, so that the laser can stably output a single-mode beam with the polarization stabilized as well. The new design will meet the application requirements of sensors including chip-scale atomic clocks, atomic gyroscopes, and so on.