Conical wavefront pumping enabling miniaturized gaseous Raman laser with high beam quality

Liu Zhensong; Xu Minghao; Wang Yanchao; Liu Yuhui; Cai Xianglong; Xu Ming; Sun Jinglu; Song Suya; Li Qingwei; Guo Jingwei

doi:10.11884/HPLPB202638.250178

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Liu Zhensong, Xu Minghao, Wang Yanchao, et al. Conical wavefront pumping enabling miniaturized gaseous Raman laser with high beam quality[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202638.250178

Citation:

Liu Zhensong, Xu Minghao, Wang Yanchao, et al. Conical wavefront pumping enabling miniaturized gaseous Raman laser with high beam quality[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202638.250178

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Conical wavefront pumping enabling miniaturized gaseous Raman laser with high beam quality

doi: 10.11884/HPLPB202638.250178

Liu Zhensong^{1, 2
,},
Xu Minghao^{1, 2},
Wang Yanchao¹,
Liu Yuhui^{1, 2},
Cai Xianglong¹,
Xu Ming¹,
Sun Jinglu^{1, 2},
Song Suya^{1, 2},
Li Qingwei^{1
,
,},
Guo Jingwei^{1
,
,}

1.
Key Laboratory of Chemical Laser, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 136023, China
2.
University of Chinese Academy of Sciences, Beijing 100049, China

Received Date: 2025-06-19
Accepted Date: 2025-11-08
Rev Recd Date: 2025-11-18

Available Online: 2025-11-25

Abstract

Abstract

Background
Different applications require lasers of different wavelengths, and Raman laser is one of effective methods to expand spectral range of lasers. Raman lasers have advantages of high conversion efficiency, excellent beam quality, excellent scalability and wide range coverage etc. However, the cumbersome size of Raman cell (especially the long length of Raman cell) deteriorates the application of Raman laser. To reduce the length of Raman cell, a short-focus lens is required, and this would lead laser-induced breakdown (LIB).
Purpose
To realize miniaturization of Raman laser devices while suppressing LIB, this work proposed a method to modulate the pump laser into a Bessel beam to achieve stimulated Raman frequency conversion using an axicon. The goal is to achieve high photon conversion efficiency (PCE) and beam quality in a compact system.
Methods
By the comparison of intensity at focus and depth of focus of f = 0.5 m focal lens and axicon, axicon with bottle angle of 2° could effectively reduce laser intensity at focus and increase the depth of focus. In this work, a pulsed 1064 nm laser was used as pump source, pressurized methane was used as Raman medium, and axicon with bottle angle of 2° was used to focus pump laser. Pressure of methane, pump laser divergence angles and diameter of pump beam were optimized to achieve the maximum conversion efficiency.
Results
In 3.5 MPa methane and 366 mJ energy of 1064 nm pump laser, 128 mJ forward Raman laser at 1543 nm was generated; the corresponding photon conversion efficiency was 50.7%, and higher output energy and conversion efficiency were expected under higher pressure and at higher pump energy. By blocking the central rounded apex of the axicon, the Raman laser pulse energy of 97 mJ can still be retained with the beam quality β=2.19. An experiment verified that the Raman cell can be designed to be 0.4 m without damaging the window. Based on the results of multiple experiments, it can be inferred that the Raman cell can be further shortened to 0.3 m without sacrificing the conversion efficiency. By axially translating the axicon within an extended cell, the forward/backward Stokes light ratio became tunable.
Conclusions
This study demonstrates the viability of Bessel beams for compact, high-efficiency gaseous Raman lasers. The conical wavefront pumping strategy mitigate LIB risks and enable system miniaturization, offering a promising pathway for practical applications.
- lasers and laser optics,
- nonlinear optics,
- axicon,
- miniaturization,
- stimulated Raman scattering

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References(29)

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