Gain performance and thermal effects of Nd:Glass and Nd,Y:SrF2 crystal

The gain performance and thermal effects of Nd:glass (N31) and Nd,Y:SrF 2 crystal are investigated and compared. The results show that, under the same pump conditions, Nd,Y:SrF 2 can provide a small-signal gain similar to that of N31. The main advantages of Nd,Y:SrF 2 are its weaker thermal effects and greater thermal-fracture limitations compared with those of N31. In this paper, the two gain media are compared in the form of rods whose diameter is 5 mm and length is 60 mm. The small-signal gain coefficients of N31 and Nd,Y:SrF 2 are 1.39 and 1.46, respectively, at a pump energy of 1.5 J/1 Hz. The pump energy is set at 1.5 J/8 Hz to experimentally investigate their thermal effects. The thermal wavefront of N31 is 0.987λ at a repetition rate of 10 Hz, whereas that of Nd,Y:SrF 2 is 0.679 λ . In thermal destructive experiments, N31 fractured at an average pump power of 15 W (1.5 J/10 Hz), whereas Nd,Y:SrF 2 fractured at a higher power of 27 W (1.5 J/18 Hz) owing to its excellent thermal conductivity, which is 7.28 times that of N31. These results indicate the potential of Nd,Y:SrF 2 crystal as a gain medium for high-repetition-rate laser amplifiers.