Advances in the Research and Laser Applications of Self-Frequency Doubling Crystals

Self-frequency doubling crystal is a kind of composite functional crystal with both laser characteristics and nonlinear characteristics. Based on the basic theory of nonlinear optics and the basic requirements of laser self-frequency doubling crystals, the development history of different rare earth ion doped nonlinear substrates LiNbO₃, YAB, LCB and ReCOB（Re=Y, Gd）crystals is reviewed in this paper. The recent progress in laser self-frequency doubling crystals is emphatically summarized. Nd:GdCOB crystal self-frequency doubling green light power of 545 nm breaks through 10 W, and Yb:YCOB crystal self-frequency doubling green light powerof 513 nm breaks through 5 W. Through electron-phonon coupling, the output of watt level self-frequency doubling yellow light laser in Yb:YCOB crystal is realized for the first time, and the output wavelength is tunable within 565-570 nm. The self-frequency doubling laser has the advantages of simple structure, high stability and strong impact resistance. It has been widely applied in many fields, such as military countermeasure, laser medical treatment and laser display, showing a broad development prospects.