Growth And Properties Of 2.79μm Chromium And Erbium Co-doped Scandium Gallium Garnet Laser Crystals

Rare earth ion Er3+ has been extensively studied due to its abundant energy level structure,which can generate various radiation wavelengths.The radiation wavelengths obtained by the transition between 4I11\2 and 4I13/2 states are in the range of 2.7-3 μm.Because of the particularity of the wavelength,the 2.79 μm laser has important application value in medical,non-linear optics and military fields.At present,there are not many crystals that can achieve 2.79 μm laser output,such as there are commercially available Cr,Er:YSGG crystal,such as Cr,Er:YSGG crystals.In addition,Cr,Er,Pr:GYSGG crystals with excellent radiation resistance ability,which have been newly developed in recent years.In this paper,the physical and optical properties of the two crystals are studied,and the laser properties of the crystals are characterized.The thermal lens effect in crystals is analyzed,and a new method for calculating the thermal focal length is established.Thermal bonding technology is used to suppress the thermal effect in crystals.The main research contents are as follows:(1)High optical quality Cr,Er:YSGG and Cr,Er,Pr:GYSGG crystals were grown by single crystal Czochralski method.The parameters of doping concentration,preparation process and crystal component size are optimized.(2)Laser output of Cr,Er:YSGG and Cr,Er,Pr:GYSGG crystals at 2.79 um is realized by flash xenon lamp pumping.The effects of doping concentration and crystal component size on laser output are compared.(3)The mechanism of thermal effect in crystal during laser operation is analyzed theoretically,and a new method for calculating thermal focal length is proposed based on the simulation results of crystal temperature distribution.(4)The maximum phonon energy of GYSGG crystal is obtained by Raman spectroscopy.The Raman vibration modes of GYSGG crystal are classified and identified.The maximum phonon energies of YAG,GGG,YSGG and GSGG are compared with those of other similar crystals.The influence of the maximum phonon energies of matrix on the upper and lower levels lifetime of Er3+doped laser crystals with high concentration is analyzed and discussed.(5)Two pure GYSGG crystals are bonded at both ends of Cr,Er,Pr:GYSGG crystals as heat sinks to improve the thermal lens effect of the crystal.The temperature distribution of the crystal was simulated and analyzed.The internal reason why the undoped GYSGG crystals bonded at the end of Cr,Er,Pr:GYSGG crystals could reduce the thermal effect of the crystal rod was explained.The work in the dissertation lays a good foundation for preparing high quality and high performance mid-infrared Cr,Er:YSGG and Cr,Er,Pr:GYSGG laser crystals.It provides a solution for improving the laser output at 2.79 um and opens up a new path for calculating the thermal focal length of crystals.