High peak power CPA laser systems can deliver now few petawatt pulses . Reaching the high energies with broad spectral bandwidth necessary for these pulses was possible by the use of large aperture Ti:Sa crystals as final amplifier media. Wide applications for these systems will be possible if the repetition rate could be increased. Therefore, thermal deposition in Ti:Sa amplifiers is a key issue, which has to be solved in case of high average power pumping. The thin disk (TD) laser technology, which is intensively developed nowadays by using new laser materials, is able to overcome thermal distortions and damages of laser crystals . TD technique also has the potential to be used in systems with both high peak and average power. For this, the commonly used laser materials with low absorption and emission cross sections, also low heat conductivity, like Yb:YAG, need to be replaced by a gain medium that supports broad enough emission spectrum and high thermal conductivity to obtain few tens of fs pulses with high repetition rates. Parasitic effects during the amplification process however seriously limit the energy that can be extracted from the gain medium and also they distort the gain profile. Nevertheless, the application of the Extraction During Pumping (EDP) technique can mitigate the depopulation losses in the gain medium with high aspect ratio . We proposed to use Ti:Sa in combination with TD and EDP techniques to reach high energies at high repetition rates, and we presented numerical simulations for different amplifier geometries and parameters of the amplification [4,5].
We present the results of the proof-of-principle experiment, where a EDP-TD Ti:Sa amplifier was tested for the first time. In our experiment, the final cryogenically cooled Ti:Sa amplifier in a 100 TW/10 Hz/28 fs laser system was replaced with the EDP-TD room temperature cooled arrangement. Amplified seed pulse energy of 2.6 J was reached only for 3 passes through TD with 0.5 J of input seed and 5 J of absorbed pump energy. We verified the excellent heat extraction capabilities of our amplifier module. Results of the scaling simulations on the base of this experiment for 100s of TW peak power laser systems operating at up to 100 Hz will be also presented.
1. Y. Chu et al, Opt. Lett. 40, 5011-5014 (2015).
2. C. R. E. Baer et al, Opt. Exp. 20, 7054-7065 (2012).
3. V. Chvykov et al, Opt. Comm. 285, 2134-2136 (2012).
4. V. Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Exp. 24, 3721 (2016).
5. V.Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Lett. 41,13, 3017 (2016).
Roland S. Nagymihály, Huabao Cao, Mikhail P. Kalashnikov, Nikita Khodakovskiy, Lutz Ehrentraut, Károly Osvay, and Vladimir V. Chvykov, "Thin Disk Ti:Sapphire amplifiers for Joule-class ultrashort pulses with high repetition rate (Conference Presentation)," Proc. SPIE 10238, High-Power, High-Energy, and High-Intensity Laser Technology III, 102380C (Presented at SPIE Optics + Optoelectronics: April 26, 2017; Published: 9 June 2017); https://doi.org/10.1117/12.2265290.5463398589001.
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