Continuous-wave And Pulse Output Performances For Yb:YAG Thin Disk Laser

LD end-pumped solid-state lasers(Diode Pump Solid State Laser, DPSSL) havethe advantages of long operational lifetime, high efficiency, compact structure and soon. Under high-power operation, the heat dissipation of the gain medium will restrictlaser output power and beam quality, in this wise, the development of DPSSL will belimited. In order to solve the thermal effect problems, the researchers design newsolid-state laser structure, including slab and thin disk. The thin disk laser utilizesend-side pumping and end-side cooling which makes the temperature gradientconsistent with the direction of the laser. This design can effectively overcome thethermal effect to receive high-power laser with high beam quality. Yb:YAG crystalhas wide absorption band, small heat load, long fluorescence lifetime as well as notsubject to the re-absorption effect and the energy conversion, which makes it becomean ideal laser medium for thin disk laser. The cavity-dumped technology can achievea constant pulse width which has nothing to do with laser gain and operationfrequency, the laser energy is completely emptied in a round-trip time. For this reason,the cavity-dumped technology can effectively improve the performance of the outputpulse laser. Based on these, this paper reports the output properties of Yb:YAG thindisk laser, including continuous-wave operation mode and pulse-transmissionoperation mode(PTM, cavity-dumped mode).Firstly, the thesis calculates of optimum design parameters for Yb:YAG thin disklaser, using the results to analyze the influence of thin disk thickness, dopingconcentration, cooling temperature, the number of pump beam passes through thecrystal for thin disk laser output properties. According to the quasi-three-level rateequation, the best ratios of the oscillation mode,s size and the pumping mode,s size atdifferent pumping powers are acquired. Lastly, using ANSYS analyzes under differentboundary conditions temperature field, thermal stress, as well as end deformation ofYb:YAG thin disk crystal. Meanwhile, the superiority for overcoming thermal effectof thin disk structure is verified compares to rod structure crystal.Based on the above theoretical optimization results, the output characteristics ofthe940nm LD is tested, using it as the pump source to achieve maximum power up to100W of1030nm continuous laser output, slope efficiency reach to55.3%, opt-opt is50.3%. To further optimize the output characteristics of continuous-wave laser output,utilizing thin disk laser system designs and implement Yb:YAG thin disk laser besttransmission experiments, the experimental results shows the best transmission T approaching12%.In the light of the rate equations for continuous-wave pumped solid-state laser,the chief parameters for Q-switched laser, such as pulse energy, pulse width and peakpower, are defined. Besides, the numerical relationship between the pulse width of thecavity-dumped laser and the switching time along with the cavity length is obtained,cavity internal parameters of cavity-dumped laser is optimized. In the cavity-dumpedexperiments, a constant20.3±0.2ns pulse duration laser is gained. And the highestrepetition rate can reach to100kHz, the corresponding average output power is42W.At repetition rates of10kHz,50kHz,100kHz, the corresponding peak powers are109.8kW,37.8kWå'Œ20.9kW, respectively.