Research On Intracavity Two-stage Cascade Pumping Sum-frequency Blue Laser

With the development of modern technology,the blue laser has become an indispensable excellent light source in many application fields,such as underwater detection and communication,biomedicine,and laser display.At present,many blue lasers have been obtained through frequency doubling,such as 456 nm,465nm,and 473 nm.In commonly used laser crystals,the transition spectrum that can be used for frequency doubling to produce blue lasers is limited,resulting in some blue lasers(such as 480-500nm)cannot be acquired by frequency doubling technology but by nonlinear sum-frequency technology.In this paper,a nonlinear sum-frequency blue laser is studied by means of intracavity two-stage cascade pumping.According to the operation mechanism of intracavity cascade pumping,this thesis analyzes and calculates the quasi-three level theory,and establishes the theoretical model of intracavity cascade pump.And according to the principle of nonlinear optical frequency conversion,we analyze the frequency conversion characteristics and optimal phase matching conditions in the nonlinear sum-frequency process.Combining the two theories of intracavity cascade pumping and nonlinear optical frequency conversion,a mathematical model that can describe the sum frequency process of intracavity cascade pumping is finally established and its output characteristics are analyzed.On the basis of the theoretical model,the components of the intracavity cascade pump sum-frequency laser system are designed.First,the characteristics of the two laser crystals,Nd:YAG and Yb:YAG,are introduced.And according to the operation characteristics of the intracavity cascade pumping and the crystal characteristics,the doping concentration and size are designed.Then,according to the optimal phase matching condition in the nonlinear frequency conversion process,the optimal phase matching angle and size of the nonlinear crystal LBO are designed.Finally,the ABCD matrix is used to simulate the transmission process of the laser beam in the cavity,and the resonator of the intracavity cascade pump sum-frequency blue laser is designed.According to the theoretical analysis and system design,the intracavity cascade pumped sum-frequency blue laser was experimentally studied.First,the 946 nm laser was realized by LD pumped Nd:YAG crystal.Then,the Yb:YAG crystal was added into the resonator to achieve the stable output of 946 nm and 1030 nm laser at the same time,and the output power was 1.29 W and 1.75 W respectively.Finally,the LBO operating in the public part of the laser resonator was employed,and a 426 m W 493 nm blue laser was successfully obtained.The corresponding laser slope efficiency was 3.38%,and the beam quality factors were 1.28 in the X-axis orientation and 1.31 in the Y-axis orientation.