Thermally-Induced Lens in an End-Pumped Cesium Laser

Diode-pumped alkali lasers (DPALs) have attracted a lot of attentions in the recent years for their high Stocks efficiency, good beam quality, compact size and near-infrared emission wavelengths. In this study, we analyze the thermally-induced lens in an end-pumped cesium cell by using the evaluated parameters such as the population density distribution, the transition rates of pump photon absorption, and the transition rates of laser photon emission, which had been obtained in our previous study. After dividing a cylindrical vapor cell into many cylindrical annuli, we calculate the refractive index n and the thermal-optic coefficient dn/dT in every annule. And then, we carry out the ray-trace to describe the propagation of an incident ray inside the vapor cell. Assuming that the incident plane-wave has a flat-top distribution, the intensity distribution of the outputted beam can be deduced. We adopted the second-moment calculation to evaluate the beam size after the ray passes through a pumped cell. Finally, the effective focal length of a thermally-induced lens was obtained for the end-pumped laser configuration. The research will be helpful to improve the beam quality of a DPAL.