Research On The Output Characteristics Of A Resonant Pumped Active Q-switched Cavity Ho:YAG/SrWO₄ Raman Laser

As modern science and technology is developing rapidly,laser with its unique advantages promotes the innovation of key technologies in various fields.In particular,due to its features of human-eye-safety,narrow pulse width,high energy and good beam spatial distribution quality,the 2?m solid-state Raman laser plays a leading role in the fields,such as military industry,spectroscopy,medical treatment,satellite remote sensing,infrared guidance and other applications.The fundamental frequency light shifts the wavelength by stimulated Raman scattering?SRS?effect.The frequency shift is determined by the vibration frequency of the Raman medium.SRS is one of the most important methods to change the frequency of the output wavelength,and greatly expands the laser spectral range.In this thesis,the output performances of Ho:YAG/Sr WO₄solid-state Raman laser are investigated.A Tm:YLF solid state laser at 1908 nm is selected as the pump source of the intracavity Ho:YAG/Sr WO₄Raman laser,a Ho:YAG laser crystal with doping concentration of 3%is chosen as the laser gain medium,and a Sr WO₄crystal is served as the Raman gain medium.In theory,the rate equation theory model for the actively Q-switched intracavity Ho:YAG/Sr WO₄Raman laser is established under the approximation of gaussian distribution.The output characteristics of Raman laser are theoretically presented through the numerical simulation.In experiment,the pumping source of resonantly pumped Ho:YAG/Sr WO₄Raman laser is first built,and the output power of the Tm:YLF laser is very stable at1908 nm.Then,the steady pulse output of the Ho:YAG laser with a central wavelength of 2122 nm is realized by using an acousto-optic Q-switching method.Finally,placing the Sr WO₄Raman crystal into the resonator,inserting the intermediate plate mirror,and replacing the 2122 nm output mirror with Raman output mirror,the mid-infrared Raman laser is successfully achieved.The central wavelengths of the Raman laser and the fundamental laser are measured to be 2640 nm and 2122 nm,respectively.The Raman frequency shift is925 cm^-1.With the Raman output mirror of 259 mm curvature radius,the maximum average output power of 580 m W is obtained at the pulse repetition frequency of 4k Hz when the Raman cavity length is 50 mm.The slope efficiency is as high as33.4%.The narrowest pulse width of Raman laser is 10.55 ns,the highest single pulse energy is 145?J,and the corresponding peak power is 13.7 kW.