Research On Multi-wavelength All-solid-state Continuous-wave Raman Laser

All-solid-state Raman lasers based on Stimulated Raman scattering(SRS)have a wide range of applications in information storage,atmospheric detection,and military radar.In recent years,multi-wavelength lasers have become one of the hot topics for research in the laser field due to strong demand for practical applications.In all-solid-state continuous-wave(CW)Raman laser,to achieve multi-wavelength laser output,it is critically important to overcome the problem of laser gain decrease caused by serious thermal effect,so as to obtain high fundamental laser and Raman gain.In order to achieve multi-wavelength CW laser output,three methods are used in this paper to improve thermal effect,including in-band pumping technology,using composite crystal as the laser gain medium and increasing pump spot size.Based on our work,multi-wavelength CW Raman laser output is successfully demonstrated in the self-Raman laser and intracavity Raman laser.Specific research topics are as follows:1.The thermal effect of all-solid-state laser is studied in detail.According to the theory of resonator transformation circle,a Nd:YVO4 fundamental laser at 1064 nm with flat-flat cavity structure is built,and the influences of different pump wavelength,different pump spot size and different laser crystal on thermal lens effect are researched in detail.2.Using Nd:YVO4 crystals with different length and specifications as the self-Raman medium,the output performances of CW self-Raman laser are researched by using 808 nm traditional pumping,and 880 nm in-band pumping,respectively.Finally,with improving thermal effect,the multi-wavelength CW self-Raman laser operation in the 1.0x μm and 1.1x μm is successfully achieved.When a 20-mm composite Nd:YVO4 crystal is in-band pumped by a 880-nm LD,a maximum Raman output power of 2.56 W is obtained under an incident pump power of 26 W.The Raman threshold is as low as 0.99 W,and the corresponding optical conversion efficiency and slope efficiency are 9.8%and 10.2%,respectively.3.Using Nd:YVO4 crystals with different length and specifications as the laser gain medium,and BaWO4 crystal as the Raman medium,the output characteristics of CW intracavity Raman laser are studied with output mirrors with different radii of curvature under the condition of in-band pumping.When a 20-mm composite Nd:YVO4 crystal is used and the radius of curvature of the output mirror is 200 mm,a multi-wavelength CW Raman laser at 1.1x μpm is achieved.With an incident pump power of 23.1 W,the highest Raman output power is 1.24 W and the Raman threshold is 2.4 W,corresponding to optical conversion efficiency of 5.4%and slope efficiency of 6%.Finally,the gain competition between different Raman frequency shifts at 890 cm-1,925 cm-1 and 332 cm-1 is investigated.