Research On Energy Amplifier Based On Sub-Nanosecond Microchip Laser

Laser amplifiers with high pulse energy and short pulse width has been widely used in many diverse disciplines,such as Laser processing technology,Laser cosmetic surgery and Lidar.The Master Oscillator Power Amplification(MOPA)technology,which combining the seed laser and the amplifying structure,not only enables features of the output pulse laser are consistent with that of the seed laser(pulse width and repetition frequency,etc.),but also ensures the amplification of the output laser energy.Thus,MOPA technology becomes the main technology in laser amplifier based on engineering applications.In this thesis,in response to the demand for sub-nanosecong high-energy laser amplifiers in medical cosmetology,a laser amplifier is developed based on the MOPA technique,in which a sub-nanosecond microchip solid-state laser is used as seed laser.It mainly includes the three following parts:1.The principle and characteristics of laser amplification technology are introduced,and the advantages of microchip solid-state lasers as seed sources are explained;the amplification process is analyzed according to theoretical equations,the effects of self-excited oscillation and return light on the amplification system during the amplification process are studied,which provides theoretical basis for the subsequent research.2.Based on the theorem of travel-wave laser amplification,the first-level single-pass laser amplification system and the first-level double-pass amplification system are designed,by selecting the seed source,pump source,and laser gain crystal.Experimental study on the laser amplification system is conducted,and the main parameters influencing the performances are analyzed.The pulse energy of the seed source entering the amplification module is 180?J.After first-level single-pass amplification and first-level double-pass amplification,the pulse energy are 12.45mJ and 169.2mJ respectively.The pulse repetition frequency during the amplification process is 10Hz.The energy generated from the self-oscillation and the energy of the return light in the amplification procedure are suppressed.The energy transfer efficiency during the amplification is increased effectively as the energy of the return light is reduced 52mJ to 1.3mJ,and the energy generated by the self-oscillation is reduced from 43mJ to 1.07mJ.3.Based on the test results of the laser amplification system,a sub-nanosecond laser amplifier engineering prototype built according to the requirements of laser medical cosmetology.The laser amplifier adopts a microchip solid-state laser as the seed source.The seed source has a wavelength of 1064 nm,a pulse width of 487.3 ps,a pulse repetition frequency of 10 Hz,and a pulse energy of 180 ?J.The prototype can switchably output laser with a wavelength of 1064nm and 532nm,in which pulse repetition frequency is 10Hz,pulse width is 496.4ps,pulse energy is 561mJ@1064nm and 330mJ@532nm,and the output spot has a uniform energy distribution.