Repetition Rate Of Yb: Yag Laser System Ase And Flow Characteristics Study

"High-efficiency, rep-rate, broad-band" DPSSL is one of the developing directions of inertial confinement fusion laser drive. With high power LD array as its pump recourse and Yb-dope laser crystal or ceramic as its laser material, the drive can achieve higher system efficiency and dependability; meanwhile fill the need of broad band transmission. The active cooling system makes the drive running in higher rep-rate.In order to obtain higher output of energy and power, the amplifier should be designed with a larger beam aperture and higher gain coefficient. This method, however, will make the Amplified Spontaneous Emission effect (ASE) more seriously. The ASE effect not only reduces the storage energy density and energy storage efficiency, but also influence the uniformity of gain distribution. The temperature of Yb material increases so markedly that not only effects light beam quality but also stops lower energy level which leads to decrease of the extract efficiency. So it's very important to reduce ASE and manage heat in optimizing the amplifier design. At the same time, in order to get high-efficiency under big energy output, the laser will run at a high energy flux nearing the damage threshold because of the characteristic of Yb material. The flux limit of both high-efficiency extract and element damage threshold will be the key point in energy-flow design of the laser system.In this paper, theoretic simulations and experiments are combined to investigate the pumping and extracting process of a pulsed energy-storage rep-rated Yb: YAG disk laser. Based on the energy-level structure of quasi-three-level Yb ion, an ASE model in pumping process and an energy extract mode are set up. The effect of ASE on energy-storage and a method to optimize parameters of amplifier are investigated specifically, which includes the aperture, doping concentration and thickness, and working temperature of the gain medium. With this method, a laser system aiming to 10HZ/20J/10ns pulse output is designed when considering the limit of laser flux. This paper also gives some new ways to reduce ASE, which are analyzed theoretically. Furthermore, we have got the experimental results of a Q-switch resonator in LD pumping Yb: YAG laser system and a Nd glass disk amplifier . By comparing the results between simulation and experiment, we proved the correction of our theory.The main innovation points are summarized as following:1. Build quasi-three-level ASE model and energy extract mode. 2. Calculation shows that energy-storage Yb: YAG laser is not suitable running in low temperature.3. The coupling of reduce ASE and thermal management.4. Designed a High-efficiency, rep-rate DPSSL system base on Yb: YAG material.5. Introduce and analyze new way in reducing ASE.