Single-ended pump laser optical conversion efficiency of 53.8%

The reporter learned from the Hefei Research Institute of the Chinese Academy of Sciences that the Jianghaihe Research Group of the Medical Laser Technology Laboratory of the Institute of Health of the Institute of Health of the Academy of Sciences cooperated with the Zhang Qingli Research Group of the Crystal Materials Laboratory of the Anguang Institute to put forward a design scheme for smooth pumping light field and temperature field uniformization, which greatly improved the laser conversion efficiency and laid an important foundation for the subsequent mass manufacturing and calibration and amplification of high-quality lasers. The relevant results were published in the international optical journal "Photonics Research".

All-solid-state end pump technology is one of the important ways to achieve compact, efficient and high-quality lasers. However, under the high repetition rate pumping, the severe laser thermal effect in the gain medium has become the main factor hindering the output power enhancement and reducing the beam quality, which is a bottleneck that is difficult to overcome in the laser industry for a long time, especially in the laser of LD single-ended pump, which is particularly prominent, the key problem is that when the crystal is uniformly doped at a high concentration, the pump light is strongly absorbed by the high concentration of doped ions at the initial end, and its intensity is rapidly reduced, resulting in the axial pumping and temperature distribution of the crystal bar is extremely uneven, and it is difficult to produce a laser with superior performance When uniformly doped crystals at low concentrations, it is difficult to obtain high laser conversion efficiency due to the small absorption coefficient. In view of this, the research team grew high-quality gradient concentration-doped crystals by improving the lifting method, designed an LD single-ended pump laser, and conducted laser experimental studies of 2 gradient-doped and 3 uniformly doped crystals. The results show that the gradient-doped crystal makes the pump light obtain more uniform absorption during propagation, greatly reduces the temperature of the pump crystal end face and the axial temperature gradient of the crystal rod, significantly reduces the thermal effect, and increases the thermal focal length at 35W pumping by 60% compared with the value of the equivalent uniformly doped crystal, which improves the effective mode volume, beam spot size and laser mode of the laser, and significantly improves the laser pulse output characteristics. The maximum laser output power reached 24.2W when running at a repetition rate of 2kHz, and the optical conversion efficiency of the laser was as high as 53.8%.

This study proves that gradient concentration doped crystals show excellent performance in terms of pumping and temperature distribution, improve the absorption of pump light at the middle end of the crystal bar, and reduce the temperature of the incident end, smooth the temperature gradient along the rod axis, significantly reduce the thermal effect, and can significantly improve the output performance of single-ended pump pulse lasers, providing a new way for future high-efficiency laser technology.

Wen/Science and Technology Daily reporter Wu Changfeng

Editor/Fan Hui