| Lasers with the wavelengths around 2.0μm are widely used in medical surgery,neuromedicine,laser radar,plastics processing,atmospheric remote sensing,optical signal processing,and as 3-4μm lasers pump light sources and other fields because of their wavelengths in the water absorption band and atmospheric output window.The doped Tm3+ laser is the main laser medium at 2.0μm.In recent years,disordered crystalline materials have attracted much interests due to their broad absorption and emission spectrum.Among them,CaGdAlO4(CGA)and CaYAlO4(CYA)disordered crystals have attracted more attention because of their high thermal conductivity,mechanical hardness,and stable chemical structure.The Tm-doped CGA and CYA laser materials not only have the advantages of the above-mentioned CGA and CYA matrix materials,but also have advantages such as a larger absorption cross section and emission cross section,and easily growth,making it popular at 2.0μm wavelengths laser materials.The research work of this paper is mainly divided into five parts:(1)Using the rate equation theory to analyze the characteristics of the main output parameters of the Tm CW and Q-switched laser;measuring the absorption and emission spectra of the Tm:CGA and Tm:CYA crystals,and the calculation of the spectral parameters providing a theoretical basis for the design and preparation of the laser resonator end mirror film system and laser experimental research.(2)According to the theory of optical film design,the end mirror film structure required for the experiment was optimized,and all the end mirrors used in this experiment were prepared by plasma vacuum sputtering method.(3)Experimental studies of continuous-wave lasers with Tm:CGA and Tm:CYA disordered crystals were carried out.For Tm:CGA crystals,the maximum output powers obtained at 1938nm and 1954nm were 3.09W and 2.41W,respectively,and the corresponding slope efficiencies were 33.7%and 28.5%,respectively.For Tm:CYA crystals,the maximum output powers obtained at 1944 nm and 1857nm were 7.62W and 5.35W,respectively,and the laser slope efficiency reached to 50.9%and 39.9%,of which 7.62W was the highest output power reported by the current Tm:CYA laser.(4)Using Cr2+:ZnSe crystal as saturable absorber,Tm:CGA and Tm:CYA passively Q-switched lasers were obtained.Among them,the maximum average power,the shortest pulse width,the maximum pulse energy and the peak power of the Tm:CGA passively Q-switched lasers operating at 1932 nm and 1851 nm are(0.67W,44ns,46μJ,1.04kW)and(0.37W,47ns,37.4μJ,0.79kW)respectively;the maximum average power,the shortest pulse width,the maximum pulse energy,and the peak power of the Tm:CYA passively Q-switched lasers operating at 1938 nm and 1857 nm are(2.65W,57.7ns,71μJ,1.305kW)and(2.37W,54.6ns,70μJ,1.17kW).Further,an etalon sheet was inserted in a Tm:CYA Q-switched laser cavity to realize a Q-switched tunable laser output in the short wavelength range from 1848 nm to 1876 nm,and a Q-switched tunable laser having an average output power of watts or more is obtained.The short-wavelength tunable Q-switched laser has potential application in the medical field and can be used for medical nerve stimulation.(5)Using the two-dimensional nano-material MoS2 as a saturable absorber,the 1948 nm(Tm:CGA)and 1923nm(Tm:CYA)Q-switched lasers was realized,and the maximum average output power,the shortest pulse width,and the maximum pulse energy,the peak powers are(0.782W,408ns,6.5μJ,15.9W)and(0.49W,480ns,4.87μJ,9.62W),respectively. |
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