| At present,2.79 ?m mid-infrared laser has widely applied in biomedicine,environmental monitoring,LIDAR,remote sensing,space research and so on.All solid-state laser system based on the 4I11/2?4I13/2 transition of erbium-doped laser crystal has attracted great interest and increasing attention by scientists all over the world.Compared with the traditional lamp pumped solid-state lasers,which exists the problems of low energy conversion efficiency,serious thermal effect and limited working frequency etc.,all solid-state lasers pumped by laser diodes have the advantages of compact structure,high gain efficiency,long working life and diversified operation modes(continuous,pulse,Q-switching and mode locking).With the development of social economy and scientific research,solid-state lasers develop towards the trend of high-repetition-rate laser output,picosecond ultra-short pulse and tunable multi-wavelength.Therefore,as the core component of solid-state lasers,many efforts need to be devoted to studying the fabrication and physical properties of laser crystals,especially when erbium-doped laser crystal has become a national military competition or even limited export products.Scandium gallium garnet laser crystals have special advantages in high power continuous wave laser output,wide band tenability and short pulse Q-switching due to its high thermal conductivity,easy growth of the large-size and excellent physic-mechanical properties.Based on the experience of the last few years and equipment of our laboratory,the growth habits,basic physical properties and laser performances of the novel Er3+-doped scandium gallium garnet laser crystals operated at 2.79 ?m have been studied.The main contents include the following four aspects:1)The doping concentrations of Er,Pr:GYSGG crystal are optimized.The effects of y-ray irradiation on their spectra and laser performances are analyzed,and the microscopic mechanism of color center defect caused by radiation is revealed.The results show that the Er,Pr:GYSGG crystal has excellent radiation resistance and can be applied in a strong radiation environment such as space.2)The 2.79 ?m high-repetition-rate and high-efficiency laser is achieved on the LD side-pumped the Er,Pr:GYSGG crystal by optimizing the experimental conditions.The thermal effect of crystal rod elements under high pump energy is analyzed by measuring the thermal focal lengths and simulating the temperature distribution.Then we compensate the thermal lens effect and improve the laser performance by combining thermal bonding and negative curvature of the end faces.The results show that the laser performances of slope efficiency,maximum output power and laser beam quality are improved on the LD side-pumped composite crystal element with negative curvature on the end-faces.3)A laser experimental device using the LGS crystal as an electro-optic Q-switch is designed,and the 2.79 pm pulsed laser with about 50 ns pulse width,100 Hz repetition rate and 0.15 MW peak output power is realized on the Er,Pr:GYSGG composite crystal rod by LD side-pumping.The results show that the LGS crystal is suitable for the electro-optic Q-switching of 2.79 ?m high-repetition-rate laser.4)The Er3+-doped LuSGG laser crystal is grown by Czochralski method for the first time,and the phase structure,crystal quality,as well as thermal,spectral and 2.79?m laser properties are characterized.The results show that Er:LuSGG is a new mid-infrared laser crystal with high efficiency and high output power,which is worthy of further study.The innovations of this dissertation are as follows:(1)The anti-radiation property of YSGG crystal is improved by replacing a part of Y3+ions with Gd3+ions,and the radiation-resistant performance of 2.79 ?m laser and the micro mechanism of color center defects are studied by y-ray irradiation of Er,Pr:GYSGG crystal.(2)The combination of thermal bonding and negative curvature grinding of the end faces is proposed to compensate the thermal lensing effect of Er,Pr:GYSGG crystal under high pump energy,which further improve the laser performance of 2.79 ?m high-repetition-rate.(3)To design an electro-optic Q-switching device using the LGS crystal,and the pulsed laser with a pulse width of 50 ns,conversion efficiency of 85.5%,repetition rate of 100 Hz and peak power of 0.15 MW is obtained on the Er,Pr:GYSGG composite crystal rod.(4)Based on the method of Lu3+ions instead of Y3+ions,the new Er:LuSGG mid-infrared laser crystal is grown by Czochralski method for the first time,and a higher power and efficiency of 2.79 ?m laser is obtained.The research work of this dissertation has important reference value for the performance improvement and exploration of new mid-infrared laser crystals operated on 2.7-3 ?m,and lay a good foundation for the practical applications of this waveband laser. |
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