Research On Output Performance Of Tm:YAP Laser Based On MoSe₂/WSe₂ Material

2μm laser is widely used in medical treatment,information transmission,gas detection,lidar,industrial processing and other fields because its central output wavelength is in eye safety and atmospheric window range,and at the same time it is in the area of multiple molecular fingerprints in the atmosphere.In recent years,with the rapid development of laser technology,the realization of a new2μm band laser by pumping a single doped Tm³⁺crystal with semiconductor lasers has become a hotspot in laser field.In this paper,Using Tm:YAP Crystal as laser gain medium and MoSe₂/WSe₂ as saturable absorber to study the output characteristics of the Tm:YAP laser in passive Q-switched.Firstly,this article conducts an in-depth study on the absorption spectrum of the Tm:YAP crystal,and recently determined that the crystal achieves the pump wavelength range of the 2μm band laser output.In order to obtain the highly efficient saturable absorber,ultrasonic assisted stripping method was used to obtain the uniform dispersion solution of MoSe₂/WSe₂ nanometer material,and the dispersion solution prepared was rotated on the Ca F₂ lens by spinning coating method to make the saturable absorber.The saturable absorber prepared was characterized by various test,and the necessary data of the saturable absorber required by the Tm:YAP laser in passive Q-switching mode are obtained.Secondly,carry out the research on the output characteristics of Tm:YAP laser in continuous operation mode.The laser cavity length is 27mm,the output mirror transmittance is 2%,the threshold power of the laser is 2.03W,the maximum output power of the laser is 2.53W when the input power is 16.95W,corresponding the laser optical-optical conversion efficiency is 16.5%;Choose an output mirror with a transmittance of 5%,At this time,the laser starts to appear when the input pump power is 2.66W.When the input pump power is 16.95W,the laser corresponding optical-optical conversion efficiency is 22.3%.Under the condition that the transmittance of the output mirror is 2.5%and the cavity length is 27mm,the laser starts to operation when the input pump power is 2.06W and the output power is 52m W.When the input pump power is 12.5W,the maximum output power of the laser and corresponding the laser optical-optical conversion efficiency are 3.0W and 28.7%,respectively.The central output wavelength of the laser is 1989.3nm,the beam quality factorM_x ² in the x-axis direction is 1.01,and the beam quality factorM_y ²in the y-axis direction is 1.03.Thirdly,based on the MoSe₂ material as a saturable absorber,the output characteristics of Tm:YAP laser in passive Q-switched mode are studied.In the experiment,the laser cavity length is 26mm,the output mirror with a transmittance of 5%is selected,when the input pump power is 16.95W,the maximum output power and the shortest pulse width of the laser are 1.084W and668ns respectively,the maximum output single-pulse energy is 5.5μJ,corresponding the laser optical-optical conversion efficiency is 7.2%.The output center wavelength of the laser is 1989.2nm.Select an output mirror with a transmittance of 5%.When the input pump power is 16.95W,the maximum single pulse energy and maximum peak power of the laser are 9.81μJ and 8.04W,respectively,corresponding the laser optical-optical conversion efficiency is12.7%.Finally,the output characteristics of the Tm:YAP laser in passive Q-switched mode were studied based on WSe₂as a saturable absorber.In the experiment,a resonator with a length of 27mm and an output mirror transmittance of 2.5%is used,when the input pump power is 12.5W,the shortest pulse width and maximum peak power of the laser obtained are 392.7ns and 28.9W res pectively,and the maximum output single pulse energy is 11.3μJ,corresponding the laser optical-optical conversion efficiency is 14%.The central output wavelength of the laser varies from 1937.5～1988.3nm with the change of input pump power.