Diode-pumped alkali lasers with a gradient temperature configuration

A diode-pumped alkali laser (DPAL) is one of the most promising candidates of the next-generation high-powered laser sources. Until now, a single-heater structure has been widely adopted to control the temperature of an alkali vapor cell in plenty of the DPAL studies. However, for an end-pumped DPAL using a single heater, most pump power can be absorbed by the gain media near the entrance window of a cell due to the large absorption cross section of atomic alkali. As a result, the temperature in the pumping area around the inputted window will be much higher than those in the other positions of the vapor cell. Such a large temperature gradient would bring about some negative influences on the output performance of a DPAL. Additionally, in the worst case, the inputted cell window may even be damaged, especially when the pump intensity becomes very high. To solve the problem, we put forward a new scheme by using a gradient heating process in which several heaters are simultaneously utilized to anneal an alkali vapor cell. In this technique, the temperature at the entrance window is set to be lower than that of the other side. Using this novel method, one can not only achieve a homogeneous absorption of pump energy along the cell axis, but also decrease the possibility of the window damage in the DPAL configuration. The theoretical simulation of the laser output features by use of multiple heaters has been carried out, and the optimum condition in temperature gradient is also discussed in this paper.