Research Of High Peak Power And High Beam Quality Fiber-Solid Hybrid Amplification MOPA Lasers

The short pulse laser with high peak power and high beam quality is of great value in the field of laser frequency conversion and laser micromachining.In recent years,with the development of semiconductor technology,the output power of the traditional solid-state laser has greatly improved,but because of the serious thermal effects,low optical conversion efficiency and beam quality difference and other factors make the all solid state laser is difficult to meet the needs of the development of science and technology in modern society.We usually use MOPA to amplify the beam quality of high beam quality and low power,so that we can get larger laser output of monopulse energy and peak power,and control the beam quality of the system.The advantages of fiber laser is good beam quality,and the use of locking technology can get the narrow pulse width,the disadvantage is in the process of power amplifier with high peak power tends to cause damage,optical fiber amplifier has obvious nonlinear effect,which affect the output performance of fiber lasers and amplifiers.Solid state laser amplifiers can withstand high peak power.Therefore,a fiber solid hybrid amplification laser system using fiber laser as seed source and solid amplifier as amplification stage is proposed in this paper.This dissertation focuses on the related theories and techniques of using picosecond fiber seed sources with side-pumped rod-like Nd:YVO4 crystals and side-pumped rod-like Nd:YAG crystals to magnify the order of milliwatts to obtain optical fibers with high peak power and high beam quality-Solid and hybrid amplification picosecond laser system.In a fiber-to-solid hybrid amplification MOPA system,the fiber seed light needs to be power amplified using a solid-state amplification module with high gain.For the solid-state amplification module,this thesis uses a mixed amplifier structure design of the end-pumped Nd:YVO4 amplifier module and side-pumped Nd:YAG amplifier module.The main emission peak of Nd:YAG crystal is 1064.5 nm and the spectrum is narrow.The main emission peak of Nd:YVO4 crystal has a wavelength of 1064.3 nm and a wide spectral line.The emission line of Nd:YVO4 crystal near 1064 nm can be completely Cover the emission line of Nd:YAG crystal.Compared with Nd:YVO4 crystal,Nd:YAG crystal has high mechanical strength,good thermal conductivity,good heat dissipation,more saturated light intensity and higher peak power,which is suitable for high power laser system.In addition,the use of pump side of the pump,the pump light from the side of the laser crystal pump,pump area,high pump power,it is easy to achieve high power output,so in order to obtain higher peak power,in this paper A first stage of end-pumped Nd:YVO4 and side-pumped Nd:YAG hybrid amplification system.In a solid state amplifier,under high-power pumping conditions,the intense thermal lens effect is formed due to the concentration of pump light in a small volume of the laser gain medium.The spherical aberration effect of the thermal lens can seriously affect the beam quality of the output light,Especially in two-way amplifiers.Therefore,the spherical aberration introduced in the amplifier must be compensated.In this paper,the spherical aberration introduced in the amplifier is compensated by the spherical aberration self-compensation theory in the end-pumped Nd:YVO4 and side-pumped Nd:YAG laser systems.Using a fiber seed source with a repetition rate of 50 kHz,a pulse width of 3.9 ps and an average power of 10.9 mW,two-stage solid-state two-way amplification was used to obtain a laser output with an average power of 27.65 W and a peak power of 65 MW.The first stage amplifier is an end-pumped Nd:YVO4 amplifier stage,the second stage amplifier is a side-pumped Nd:YAG amplifier stage.The output laser beam quality factor M2 = 1.30 is obtained by controlling the beam quality of the final laser output by using the double-pass amplification structure designed by spherical aberration compensation and adjusting the fill factor in the amplification stage.This hybrid amplification method overcomes the shortcoming that Nd:YV04 crystal can not withstand the high peak power,and not only obtains laser output with high peak power,but also ensures good beam quality.Domestic and foreign research on optical fiber-solid hybrid amplification system,do not use this end-pumped Nd:YVO4 amplifier and side-pumped Nd:YAG amplifier amplification amplification.The use of Nd:YVO4 and Nd:YAG amplifiers for optical fiber seed light mixing amplification,while using spherical aberration compensation theory to control the beam quality has not been reported.