Power and energy scaling of an acousto-optically Q switched Raman deep-red laser

• Published in: Optics letters 2022-09, Vol.47 (18), p.4754-4757
• Main Authors: Zhao, Hui, Jiang, Cong, Li, Keyin, Zhou, Haiqiong, Zhu, Siqi, Yin, Hao, Li, Zhen, Chen, Zhenqiang, Dai, Shibo
• Format: Article
• Language: English
• Subjects: Energy conversion efficiency; Lasers; Lithium; Nanosecond pulses; Neodymium lasers; Optimization; Phase matching; Pulse duration; Raman lasers; Repetition; Second harmonic generation
• ISSN: 0146-9592; 1539-4794
• DOI: 10.1364/OL.468820

An efficient high-power nanosecond pulsed deep-red laser at 745 nm is produced by intracavity frequency-doubling an acousto-optically Q switched Nd:YLF/KGW Raman laser using a lithium triborate (LBO) crystal. The critically phase-matched type-I LBO crystal with an optimized length of 25 mm is adopted to enable efficient second-harmonic generation and to suppress unwanted cascaded Stokes fields. Under a repetition rate of 4 kHz, the maximum average output power of 4.1 W is obtained with the launched pump power of 50 W, resulting in an overall optical power conversion efficiency of 8.2%. The average beam quality factor is determined to be M 2 = 1.46. The pulse energy is scaled up to 3.3 mJ at the repetition rate of 1 kHz, corresponding to a pulse width of 4.2 ns and a peak power of up to 0.8 MW. Moreover, we theoretically investigate the dependence of the conversion efficiency on the walk-off angle as well as the fundamental and first-Stokes losses, which will guide further optimization of experimental devices.