The 30th International Conference on Advanced Laser Technologies LS-O-9
ALT'23
Nonlinear absorption and refraction study of quaternary barium chalcogenide BaGa2GeSe6 crystal at 1053 nm in nanosecond regime
N. Kostyukova1'2' *, E. Erushin1'2, A. Boyko1'2, A. Kostyukov1, A. Kiryakova2, D. Badikov3
1-Novosibirsk State University, Russia, 630090, Novosibirsk, 1, Pirogova str.
2- Institute of Laser Physics of the SB of the RAS, Russia, 630090, Novosibirsk, prosp. Ac. Lavrentiev, 15B 3- Kuban State University, 149 Stavropolskaya Str., 350040 Krasnodar, Russia
* n. [email protected]
Barium chalcogenide crystals are promising nonlinear media for efficient parametric down-conversion in the mid-IR range [1]. Nonlinear absorption and refraction that occur in crystals upon interaction with high-power laser radiation can lead to distortion of the transverse distribution of the laser beam intensity in the crystal and the occurrence of self-focusing effects and mismatch of the optical cavity, and thereby reduce the efficiency of conversion. Therefore, it is important to take them into account when designing optical set-ups of highly efficient mid-IR tunable optical parametric oscillators (OPOs). This work is devoted to an experimental study of the nonlinear optical characteristics of the BaGa2GeSe6 (BGGSe) crystal by Z-scan technique proposed in the work [2].
The radiation source was a diode-pumped Q-switched Nd:YLF laser produced pulses with a duration of 6 ns and energy up to 1 mJ at 1.053 ^m with repetition rate varied from 0.1 to 4 kHz. The measured beam quality factor M2 was around 1.4 and the radiation's linewidth was 227 pm (approximately 2 cm-1). The BGGSe plate was cut at 9=30° and 9=30° with wedge of all plates was no more than 10 arc seconds. The surface quality can be estimated as 60-40 scratch and dig, and surface flatness was A/6 at 633 nm. The both sides of tested plate have an AhO3 antireflection (AR) coating centered at 1053 nm. Measured P and n2-values in the BGGSe plate with nanosecond 1053 nm laser pulses at different intensity are presented in Table 1.
Table 1. Measured P and n2-values in the BGGSe plate with nanosecond 1053 nm laser pulses at 1 kHz
I, MW/cm2 Pol. ß, cm/GW n2Xl0-13, cm2/W n2X10-10, esu
49,3 e-wave 5,59 5,79 3,615
o-wave - 3,34 3,34
84 e-wave 6,58 9,37 5,85
o-wave 4,7 7,53 4,55
117 e-wave 6,71 12,57 7,86
o-wave 5,08 9,93 5,68
A strong dependence of nonlinear absorption and refraction on the radiation intensity is observed. This may be related to thermal effects, which are most appeared at nanosecond pulses [3].
This work was supported by the Russian Science Foundation (Project no. 23-22-00368).
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[2] M. Sheik-Bahae, A. A. Said, E. W. Van Stryland. High-sensitivity, single-beam n2 measurements, Opt. Lett., vol. 14, p. 955 (1989).
[3] T. Olivier, F. Billard, and H.Akhouayri, Z-scan theoretical and experimental studies for accurate measurements of the nonlinear refractive index and absorption of optical glasses near damage threshold, Proc. SPIE 5273, Laser-Induced Damage in Optical Materials: 2003, (10 June 2004).