Science Island Team Makes New Progress in Gradient Concentration Nd:YAG And Nd:GdYAG Crystal Preparation And Laser Performance Research

Recently, researcher Zhang Qingli's group of Anguang Institute of Hefei Institute of Materials, Chinese Academy of Sciences and researcher Jiang Haihe's group of Health Institute of Chinese Academy of Sciences have further cooperated in the study of gradient concentration laser crystal growth and laser performance, and have grown Nd:YAG and Nd:GdYAG laser crystals with different gradient concentrations by using vesicle-like method, and Nd:GdYAG laser performance is better than that of the approximate gradient concentration Nd:YAG crystal, and relevant research results have been published in "Gradient concentration laser crystal growth". Nd:GdYAG has better laser performance than Nd:YAG with approximate gradient concentration, and the related research results have been published in Optics and Laser Technology, an internationally renowned optics TOP journal, under the title of "Growth and Laser Performance of Nd:YAG Series Crystals with Gradient Concentration".
The luminescence performance of activated ions in laser crystals is generally affected by factors such as ligands and crystal fields in matrix crystals. The energy level structure of gadolinium ions (Gd 3+) is relatively simple, and there is no overlap of the energy levels of 4F 3/2, 4I 15/2, 4I 13/2, and 4I 11/2 with those of neodymium ions (Nd 3+), so that no cross-relaxation of the energy levels and no absorption will be generated, and the luminescence performance of the crystals can be realized and regulated. The research team doped Gd 3+ into Nd:YAG crystals with gradient concentration to optimize the luminescence performance, and used the vesicular growth method to grow Nd:YAG and Nd:GdYAG laser crystals with different gradient concentrations. The concentrations of Nd:YAG and Nd:GdYAG were 0.17-0.38 at% and 0.95-2.86 at%, and the concentrations of Nd:GdYAG were 0.18-0.32 at% in the isotropic portion, as determined by laser stripping inductively coupled plasma mass spectrometry (ICP-MS). The absorption coefficients at 808 nm show an increasing trend at different positions along the crystal growth direction, which further indicates that the Nd 3+ concentration in the crystals has a gradient distribution. A 3 40 mm laser bar was removed from the equal diameter part of three crystals, rounded and end-face processed, heat-sink designed and processed, end-face pumped, with the low-concentration end as the incident end and the flat cavity structure, and the laser performance tests were carried out. 0.17-0.38 at% Nd:YAG and 0.18-0.32 at% Nd:GdYAG laser slanting efficiencies were 52.8% and 55.0%, and the maximum output power was 0.17-0.38 at% and 0.18-0.32 at% Nd:GdYAG, respectively. The laser slant efficiency of 0.95-2.86 at% Nd:YAG is 47.4%, and the maximum output power is 6.82 W. When the high concentration end is the incident end, the laser performance decreases significantly.
The experimental results show that the gradient concentration crystal can effectively improve the laser output efficiency, and the laser performance of gradient concentration Nd:GdYAG is better than that of the approximate gradient concentration Nd:YAG crystal, and the gradient concentration laser crystal is expected to provide a new type of crystalline material basis for high-efficiency laser technology.
This research work was supported by the National Natural Science Foundation of China (NSFC) and the Chinese Academy of Sciences (CAS) Youth Innovation Promotion Committee.

Concentration distribution of isodiameters of crystals

Growing crystal blanks

Absorption spectra at different positions in the growth direction

Variation of laser output power with pump power in three kinds of crystal bars