Research On Solid Raman Lasers Based On ZnWo₄ Crystal

Stimulated Raman Scattering?SRS?is a kind of high-efficiency optical frequency conversion technology.The wavelength of scattered light is determined by the wavelength of pump light and Raman medium.In the comparison of traditional gas and liquid Raman media,solid Raman media has the characteristics of small volume,large particle concentration,large Raman gain coefficient,and good thermal conductivity.The emission spectrum of a solid Raman laser greatly broadens the spectral range of the laser,and the spectrum extends from the ultraviolet to the near infrared.Over the past period of time,Raman crystals have entered the field of scientific research.Scientifically,they prefer high-efficiency,simple,and high-gain crystals.Ba?NO₃?₂ has the highest gain coefficient among numerous Raman crystals.Particularly popular.The Ba?NO₃?₂ crystal does not meet other requirements and is not practical at long wavelengths.Therefore,the search for newer Raman crystals is imminent,including the optical properties,thermal properties,and damage thresholds.Such as physics and chemistry put forward higher requirements.So far,BaWO₄,PbWO₄,SrWO₄,YVO₄,etc.have been reported as very excellent Raman crystal materials.The thermal conductivity coefficient of Zn WO₄ in the direction of the c-cut crystal axis reaches 5.412 Wm^-1K^-1,which is twice that of BaWO₄ and SrWO₄.The optical and thermal properties of ZnWO₄ are excellent.ZnWO₄ is a potential new Raman material.Only simple Raman spectroscopy experiments have been reported for ZnWO₄.The work of Raman lasers for ZnWO₄ has not been specifically developed.In this paper,Nd:YAG and Tm:YLF are selected as the laser gain medium and ZnWO₄ crystals are Raman gain media.The output characteristics of Raman laser are studied by changing cavity structure and laser element.The main contents of this thesis are as follows:I Using a concave-plane resonance cavity,when the repetition rate is fixed at 9 kHz and a pump power of 22.1 W,the maximum output power is 886 mW,and the corresponding light-to-optical conversion efficiency is 4%first-Stokes Raman laser.The corresponding pulse width,single pulse energy,and peak power are 2.245 ns,98.4?J,and 43.8 kW,respectively.II Concave-flat resonators are used.Under the light pumping light of 14.2 W and a low repetition rate of 9 kHz,the second-Stokes Raman laser is operated optimally.The1312.6 nm second-Stokes Raman laser with an average power of up to 670 mW achieves a corresponding light-to-optical conversion efficiency of 4.7%,the corresponding single pulse energy,and peak power are 74.4?J,and 22.6 kW,respectively.Using a concave-plane resonant cavity,a pump with 14.2 W of light and a repetition rate of 9 kHz was used to achieve optimal operation of a third-Stokes Raman laser with a maximum power of 210 mW at 1490.6 nm,a third-Stokes Raman laser,and the corresponding light-to-optical conversion efficiency is 1.5%,the corresponding single pulse energy,and peak power are 23.3?J,and 6 kW,respectively.III Adopt U cavity structure,Q switch repetition rate 2.5 kHz,pumping power 30 W,we have a wavelength of 2254 nm maximum power of 184 mW of first-stokes.Pulse width,single pulse energy and peak power are:5.755 kw,5.755 ns,73.6 uJ,respectively.The beam quality of the first-Stokes Raman laser?M² factor?was 1.32and 1.46 in the horizontal and vertical directions,respectively.With an Lcavity structure,Q-switch repetition rate of 3 kHz,pumping power 30 W,we obtained a first-Stokes Raman laser with a maximum power of 173 mW at 2294 nm,corresponding to the pulse width and single pulse,The energy and peak power are:2.280 ns,57.6?J,and25.3 kW.