| Laser is a new type of light sources with high brightness,good direction and good monochromatic property.In recent years,laser technology has developed rapidly,and various new lasers have appeared and been widely used in many fields.Dual-wavelength laser is one of the hot topics of laser technology at home and abroad.The orthogonal polarization dual-wavelength laser has important applications in the fields of holographic interferometry,differential absorption laser radar(DIAL),safe communication,and terahertz(THz)radiation.In this thesis,a dual-cavity resonant and dual-crystal Yb:YAG laser based on laser diode(LD)end-pumped is designed.This laser can obtain orthogonal linearly polarized dual wavelength laser output at 1030nm and 1050nm.The main content of the thesis includes the following parts:Firstly,the recent advances of orthogonal polarized two-wavelength laser at home and abroad are analyzed.The optical and physical properties of Yb:YAG laser crystal are introduced.The working principle of the 1030nm quasi-three-level laser system and the 1050nm four-level laser system of the Yb:YAG crystal is analyzed.According to the threshold formula,the relation between the reflectance of the output coupling mirror and the output of the two-wavelength laser is derived.The causes and solutions of thermal effects in Yb:YAG crystals are summarized.Model building and thermal field simulation of the Yb:YAG crystal are performed using ANSYS finite element analysis software.Secondly,a dual-cavity resonant and dual-crystal Yb:YAG laser scheme is designed.The 940nm LD was used as the laser pump source.The laser resonator is divided into a straight cavity and a right angled cavity by using a polarization spectroscopic prism PBS.A Yb:YAG laser crystal is placed in each cavity to emit a single wavelength laser of 1030nm and 1050nm respectively.After the polarization splitting and combining of PBS,the orthogonal linear polarization double wavelength lasers at 1030nm and 1050nm are obtained.Thirdly,the LD end-pumped single crystal Yb:YAG laser experimental system is established.With the rise of pump power,there will be three wavelength output situations:1030nm single wavelength oscillation,1030nm and 1050nm simultaneous oscillation,and 1050nm single wavelength oscillation.The reasons for the occurrence of three wavelength conditions are analyzed.The variation law of wavelength with pump power is obtained.The sample standard deviation of power stability of 10min is 17.9.The effect of the crystal cooling temperature on the polarization characteristics of the laser is investigated.The results show that both 1030nm and 1050nm laser are unpolarized light at the cooling temperature of 10℃.Fourthly,dual-cavity resonator and dual-crystal Yb:YAG laser experimental system is set up.The wavelength output of three cases in the straight and rectangular cavity is achieved by adjusting the double cavity injection current at the cooling temperature of 10℃.When the pump current is 3.4-4.2A,the linear cavity outputs the p polarized laser at 1050nm,and the rectangular cavity outputs the s polarized laser at 1030nm.When the pump current is 6.4-8.6A,the linear cavity outputs the p polarized laser at 1030nm,and the rectangular cavity outputs the s polarized laser at 1050nm.The laser slope efficiency is 7.1%and the pump power conversion efficiency is 2.9%.The sample standard deviation of power stability for two-wavelength simultaneous oscillation in 10min is 8.9.In conclusion,this dual-cavity resonator and dual-crystal Yb:YAG laser realizes the output of orthogonal polarized dual-wavelength laser at 1030nm and 1050nm,which solves the problem of gain competition of single-crystal dual-wavelength laser,and can be widely used in laser precision measurement and other fields. |
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