CC BY
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ALT'23 The 30th International Conference on Advanced Laser Technologies
LS-O-16
High-power, high-efficiency Nd:YAG laser CW mode-locked with
CVD-graphene
D.P. Tereshchenko (1), M.N. Ershkov (2), S.A. Solokhin (2), Slukhov S.A. (2), S.N. Smetanin (1), A.G. Papashvili (1), M.G. Rybin (1,3), A. Ismaeel (3), E.D. Obraztsova (1,3)
1- Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia 2- Kovrov State Technological Academy named after VA. Degtyarev, Kovrov, Russia 3- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
High-power, high-efficiency diode-end-pumped Nd:YAG laser with CW mode-locking by single-layer CVD-graphene is experimentally investigated. Output radiation with average power of up to 1.7 W at optical-to-optical and slope efficiencies of 19.8% and 24% respectively is obtained.
Ultrafast mode-locked solid-state lasers have widespread applications in many different research fields, such as medical applications, microscopy, military, optical communication, material processing and so on. Passive techniques of mode-locking make the ultrafast lasers simpler and more compact. Recently, graphene based saturable absorbers are drawing more and more attention due to its unique properties, such as wideband tunability, fast saturable absorbability, and simple and low-cost fabrication. Usually graphene mode-locked solid-state lasers have low average power (< 1 W) or low optical efficiency (< 10 %). The highest output average power of Nd:YAG laser CW mode-locked with graphene was as high as 2.1 W, but optical efficiency was low (4.9 %) [L. Li et al, Opt. Commun. 315, 204 (2014)]. To date, the highest optical efficiency of a graphene-mode-locked solid-state laser with 1-W level output power is 16.2 % for Nd:YVO4 [L. Zhang et al, Laser. Phys. 21, 2072 (2011)]. Further increase in power characteristics was limited by thermal load of the laser crystal. In present work, the laser design has been improved for high-power operation. The AR-coated, 8-mm long, 1 at. % Nd:YAG crystal with water cooling was chosen as the active medium for 808-nm diode end-pumping due to better thermo-optical characteristics. Internal losses of the Nd:YAG laser cavity were minimized by using a high-quality single-layer CVD-graphene applied directly on the end cavity mirror. Reflectivity of the output coupler, radii of curvature of the internal cavity mirrors, and the laser cavity length were optimized for input power of CW diode pumping of up to 9 W. The highest output average power of the laser was as high as 1.7 W (at 8.6 W pumping) in CW mode-locking regime at optical-to-optical and slope efficiencies of 19.8% and 24.0% respectively. The highest individual picosecond pulse energy was as high as 20.7 nJ for a repetition rate of 82 MHz at diffraction limited beam quality. Increasing the pump power higher than 9 W led to decreasing the optical efficiency due to a thermal lens in the Nd:YAG crystal.
The laser investigations were supported by Russian Science Foundation - Project No 22-22-20092. The graphene films preparation was supported by Russian Science Foundation - Project No 21-72-20050.
