Research Of Picosecond Laser Amplifier Based On Grazing Incidence Slab Geometry

With the rapid development of Diode Pump Solid State Laser(DPSSL)technology,especially the development of diode pumped slab laser amplifier,the output power of the laser has been greatly improved,and also the beam quality has been improved dramatically.Because the Diode Pump Slab Amplifier has the characteristics of high efficiency,compact structure,good beam quality and used in many fields of industrial processing,nonlinear frequency conversion,which is the current research focus in the field of laser.Usually,using the Master Oscillator Power Amplifier(MOPA)to enhance the output power to meet the actual application needs because the output power of the seed source is relatively low.In recent years,the technology of amplifying low power seed source based on slab amplifier has attracted much attention in the world.In this thesis,we study the technology of low power passively Q-switched microchip picosecond seed source using Nd:YVO4 slab crystal to obtain a high gain,high quality solid-state picosecond laser amplifier.Compard with the end pumped rod structure,the slab medium can effectively reduce the thermal distortion and thermal stress in the medium.The cooling surface of the slab medium is large,the thickness is thin,the surface area to volume ratio is large,the heat dissipation of the crystal can be realized efficiently and the temperature gradient in the crystal can be reduced.The vertical direction has a compensation effect on the slab structure by analyzing the thermal induced wavefront distortion and thermal lens effect caused by the refractive index of the grazing incidence slab,which has little influence on the thermal effect of the slab.When the light spot in the vertical direction is small,the extraction is higher and the beam quality will hardly deteriorate.In this paper,the relationship between the incident angle,the horizontal width of the seed light on the pump surface and the external spot size are analyzed theoretically.The new liquid pure metal material is used as heat contact material and the experimental results show that the heat dissipation performace of the liquid pure metal material is better than that of the conventional thin indium.Based on a Semiconductor Saturable Absorber Mirror(SESAM)and passively Q-switched microchip seed laser,the low power seed laser with a pulse duration of 90 ps at a repetition rate of 100 KHz with the beam quality factor M2 of 1.16 is amplified by single-pass Nd:YVO4 bounce amplifier,finally an output power of 11.4 W is obtained with the optical-optical extraction efficiency of 20.7%.The beam quality factor Mx2= 1.25,My2=1.20?Reducing the pump power density by increasing the vertical size of the pump,an output power of 13 W is obtained with the optical-optical extraction efficiency of 23%,achieving pulse peak power of 1.2 MW and pulse energy of 130 ?J.The beam quality factor M_x~2=1.30,M_y~2 = 1.28?...