Research On Tm:YVO₄ Solid-state Laser At 2?m

Tm:YVO₄ laser crystal can produce 1.94?m laser,belonging to the mid-infrared 2?m band.The output wavelength is in the atmospheric window,which has great advantages in atmospheric transmission.The 2?m band laser can be absorbed by NO₂gas molecules,CO₂ gas molecules,etc.Therefore,it has a very important role and application prospect in laser remote sensing,environmental monitoring,laser communication,etc.At the same time,it plays an important role in laser radar,laser imaging,laser ranging,material processing,photoelectric countermeasure and laser medicine.Based on the above,2?m wave band is a hot spot in the field of solid laser research.Tm:YVO₄ laser crystal is a tetragonal uniaxial crystal with zircon structure.With high light transmittance,wide light transmission range,large birefringence coefficient,the crystal has excellent physical,chemical and mechanical properties and is easy to process and produce.However,Tm:YVO₄ crystal will produce strong thermal lens effect under high power pumping,so research and analysis are needed in the design of laser resonant cavity and the experiment of laser.Thus,based on studying the temperature field distribution and thermal lens of Tm:YVO₄ laser crystal,this paper conducts theoretical and experimental research on Tm:YVO₄ laser crystal continuous wave laser and acousto-optic Q-switched laser,and analyzes the output characteristics of laser with different parameters.In this paper,the temperature field distribution and thermal lens effect of Tm:YVO₄laser crystal are studied in detail.The heat conduction equation can describe the temperature field distribution inside the laser crystal,analyze the front and rear end faces and the internal temperature field of the laser crystal,and analyze the influence of the laser crystal length and pump laser power on the internal temperature field of the laser crystal.The thermal lens effect in laser crystal is experimentally studied through collimated beam detection.The output characteristics of Tm:YVO₄ CW laser are studied.Firstly,the resonant cavity of Tm:YVO₄ CW laser is analyzed under the framework of ABCD matrix theory,and the laser resonant cavity is optimized.Secondly,the paper studies the continuous wave laser,including the effect of crystal quality on laser output,the effect of output mirror transmittance on laser output,the effect of the length of crystal and bonded crystal on output characteristics.Finally,the study measures the beam quality of laser by knife-edge method.In the experiment,Tm:YVO₄ laser crystal with 15mm long and3%doping concentration has good output performance.The optical efficiency of 1.94?m continuous laser with pump power of 28W and output of 1.85 W is 6.6%and the beam quality factor is 1.38.The output characteristics of Tm:YVO₄ acousto-optic Q-switched laser are studied.Firstly,the resonant cavity of Tm:YVO₄ acousto-optic Q-switched laser is analyzed under the framework of ABCD matrix theory,and the laser resonant cavity is optimized.Secondly,the acousto-optic Q-switched laser is experimentally studied,including the effects of repetition frequency,transmittance of output mirror and different crystals on the output characteristics of pulsed laser.In the experiment,Tm:YVO₄ laser crystal with a doping concentration of 3%and a length of 15 mm has the best output performance.When the pump power is 28 W,the optical-optical conversion efficiency of the 1.94?m laser with power of 1.82 W is 6.5%.The corresponding shortest pulse width is 115 ns.The pulse energy is 364?J,and the peak power is 15.83 k W.The output performance of different types of laser crystals is quite different.Using bonded crystals can effectively improve the output performance of laser crystals.