Development Of Intra-cavity Cascaded Pumped Nd:GdVO₄/Yb:YAG Laser

With the advancement of human science and technology,it shows great demand for dual-wavelength lasers in the fields of medical cosmetology,lidar,nonlinear mixing,laser detection,terahertz waves and etc.At present,dual-wavelength lasers of about 1?m on the market generally have problems such as gain competition or complex structures,which make it difficult to promote them in practical applications.Meanwhile,it is urgent to develop dual wavelength lasers with more wavelength combinations,due to the different needs of different industries.To tackle the above problems,this paper has developed a dual-wavelength laser with a working frequency of 912nm/1030 nm,using a compact cavity cascade pump structure.In order to reduce the pump threshold of the dual-wavelength laser and improve the output efficiency of the system,this paper starts with the theory of the operation of the cascade-pumped dual-wavelength laser in the cavity,and solves the rate equation of the quasi-three-level system involved.Besides,the three-level pumping threshold conditions and output power are discussed in detail under the space-independent and space-dependent models in the paper.A mathematical theoretical model of the intracavity cascade-pumped dual-wavelength laser is established and its characteristics is researched.In addition,the thermal effects of crystal heating during the operation of the dual-wavelength laser is briefly illustrated.According to the characteristics of the intracavity cascade pump technology and the theoretical model,we have optimized the important system elements in the dual-wavelength laser.The concentrations and sizes of the Nd:GdVO₄ and Yb:YAG crystals has been optimized based on the basic Characteristics.Using ABCD matrix,we has studied the backand-forth propagation of the two-wavelength Gaussian beam in the cavity and determined the cavity parameters.Combined with theoretical analysis,the optimal coupling transmittance of the dual-wavelength laser output mirror has been studied,and its optimal transmittance at 912 nm and 1030 nm has been modeled and analyzed using Matlab software.Based on theoretical analysis and design,experiments are set up.First,a 912 nm laser output experiment was performed,and a stable 912 nm laser with a maximum output of 3.81 W was obtained.On the basis of this,a 912nm/1030 nm dual-wavelength output experiment was performed in the cavity.Finally,when the LD pump power of 808 nm is 25 W,the 912 nm laser with 0.97 W and the 1030 nm laser with 1.33 W were obtained.The corresponding light-to-light conversion efficiency was 9.2%.The beam quality factors M² of the 912 nm and 1030 nm lasers were 1.19 and 1.23 respectively.