為了獲得高平均功率同調光，可藉由提升TDL架構的pump laser-TDL光轉換效率或是提高seed從MA架構獲得的增益來達成。以中山大學提供的Yb:YAG樣本作增益介質，通過自行設計的激發腔與晶體散熱系統，本論文初步建立了TDL架構與MA架構。對於TDL架構，其在共振腔長度為270 mm、輸出耦合鏡之曲率半徑與反射率分別為500 mm及95%、晶體濃度為13.3 at%時，藉由50 Hz repetition rate、duty cycle 10%，平均功率43.6 W的pump laser能夠有平均輸出功率為22.68 W，slope efficiency為61.3%，pump laser-TDL光轉換效率52%。對於MA架構，建立了二通放大器，使1040 nm、pulse energy 25.68 nJ的seed光能有1.8倍的增益，驗證了在平均功率12.4 W的pump laser，晶體能有1.55×10^21 (cm^(-3))的雷射上能階電子密度。通過二通放大結果，可推估seed laser pulse energy 2.568 μJ，其中心波長改為1030 nm且FWHM 1nm，能在趟數增加至9趟時有最大輸出能量0.5 J。

To achieve high average power coherent light beam, the pump laser-TDL light transfer efficiency of a TDL system or the gain of a MA system should be enhanced. This research builds up a fundamental TDL system and a MA system, which based on the Yb:YAG samples offered by NSYSU as gain medium with self-designed pump cavity and crystal cooling system. For TDL system, this research shows that a 13.3 at.%, 300 μm Yb:YAG with a 270 mm long resonator which output coupler’s radius of curvature and reflectivity is 500 mm and 95%,respectively, pumped by a 50 Hz repetition rate,duty cycle 10%,average power 43.6 W pump laser, can deliver TDL, which average output power comes to 22.68 W and the slope efficiency is 61.3%, the pump laser-TDL light transfer efficiency is 52%. For MA system, a 2-pass amplifier is built to let a 1040 nm, pulse energy 25.68 nJ seed has a 1.8x amplification, which proves that the upper laser level density should be 1.55×10^21 (cm^(-3)) when pumped by an average power 12.4 W pump laser. By the results of 2-pass amplifier, the simulation shows a 9-pass amplifier can amplify the seed laser, which central wavelength is 1030 nm and FWHM 1 nm , pulse energy 2.568 μJ, to 0.5 J.

1. Patel, C.K.N., Continuous-Wave Laser Action on Vibrational-Rotational Transitions of CO2. Physical Review, 1964. 136(5A): p. A1187-A1193.
2. Maiman, T.H., Stimulated Optical Radiation in Ruby. Nature, 1960. 187(4736): p. 493-494.
3. Hecht, J., Short history of Laser development. Applied optics, 2010. 49: p. F99-122.
4. Geusic, J.E., H.M. Marcos, and L.G. Van Uitert, Laser Oscillations in Nd-DOPED Yttrium Aluminum, Yttrium Gallium and Gadolinium Garnets. Applied Physics Letters, 1964. 4: p. 182-184.
5. Kay, R.B., et al., Derivation of the Frantz-Nodvik Equation for Diode-Side-Pumped Zigzag Slab Laser Amplifiers With Gaussian Laser Mode and Pump Beam Shapes. IEEE Journal of Quantum Electronics, 2011. 47(5): p. 745-749.
6. Giesen, A., et al., Scalable concept for diode-pumped high-power solid-state lasers. Applied Physics B, 1994. 58(5): p. 365-372.
7. Speiser, J., Thin disk lasers: history and prospects. 2016. 98930L.
8. Saravani, M., A.F.M. Jafarnia, and M. Azizi, Effect of heat spreader thickness and material on temperature distribution and stresses in thin disk laser crystals. Optics & Laser Technology, 2012. 44(4): p. 756-762.
9. Uusikallio, S., et al., Determination of effective heat transfer coefficient for water spray cooling of steel. Procedia Manufacturing, 2020. 50: p. 488-491.
10. Radmard, S., A. Moshaii, and K. Pasandideh, 400 W average power Q-switched Yb:YAG thin-disk-laser. Scientific Reports, 2022. 12(1): p. 16918.
11. Huang, Y., et al., A multi-pass pumping scheme for thin disk lasers with good anti-disturbance ability. Optics Express, 2015. 23.
12. Yingnan Peng, Z.W., Dehua Li, Jiangfeng Zhu, Zhiyi Wei, A 12.1-W SESAM mode-locked Yb:YAG thin disk laser. Chin. Phys. B, 2016. 25(5): p. 54205-054205.
13. Dai, L., et al., High-efficiency, high-repetition-rate cavity-dumped Q-switched Yb:YAG thin-disk laser based on a 72-pass pump module. Optics Express, 2022. 30.
14. Negel, J.-P., et al., Ultrafast thin-disk multipass laser amplifier delivering 1.4 kW (4.7 mJ, 1030 nm) average power converted to 820 W at 515 nm and 234 W at 343 nm. Optics Express, 2015. 23(16): p. 21064-21077.
15. Koerner, J., et al., Measurement of temperature-dependent absorption and emission spectra of Yb:YAG, Yb:LuAG, and Yb:CaF2 between 20°C and 200°C and predictions on their influence on laser performance. Journal of the Optical Society of America B, 2012. 29(9): p. 2493-2502.
16. Lin, Z., et al., Amplified spontaneous emission model of thin disk laser with nonuniform temperature distribution. Journal of the Optical Society of America B, 2017. 34(3): p. 625-632.
17. Yang, P., P. Deng, and Z. Yin, Concentration quenching in Yb:YAG. Journal of Luminescence, 2002. 97(1): p. 51-54.
18. Cardinali, V., et al., Determination of the thermo-optic coefficient dn/dT of ytterbium doped ceramics (Sc2O3, Y2O3, Lu2O3, YAG), crystals (YAG, CaF2) and neodymium doped phosphate glass at cryogenic temperature. Optical Materials, 2012. 34(6): p. 990-994.
19. Koechner, W., Solid-State Laser Engineering. 6 ed. Springer Series in Optical Sciences. 2006: Springer New York, NY.
20. Furuse, H., R. Yasuhara, and K. Hiraga, Thermo-optic properties of ceramic YAG at high temperatures. Optical Materials Express, 2014. 4.
21. Paschotta, R., Gradient-index Lenses, in RP Photonics Encyclopedia.
22. Vlasova, S., et al., Investigation of temperature dependence of radiation from semiconductor lasers and light emitting diodes. IOP Conference Series: Earth and Environmental Science, 2020. 539(1): p. 012137.
23. Wendelstorf, J., K.H. Spitzer, and R. Wendelstorf, Spray water cooling heat transfer at high temperatures and liquid mass fluxes. International Journal of Heat and Mass Transfer, 2008. 51(19): p. 4902-4910.
24. Fukuda, M., et al., Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy. Applied Physics B, 2010. 100(2): p. 377-382.
25. Nagisetty, S., et al., Lasing and thermal characteristics of Yb:YAG/YAG composite with atomic diffusion bonding. Laser Physics Letters, 2017. 14: p. 015001.
26. Lin, G.-T., Research on the Crystal Growth and Properties of Yb:Y3Al5O12 Grown by Czochralski Pulling Technique. 2023, Department of Materials and Optoelectronic Science,NSYSU. p. 61.