Research Progress of Single-Frequency Continuous-Wave Laser Based on Single-Crystal Fiber

doi:10.16553/j.cnki.issn1000-985x.2026.0030

Abstract

Abstract: All-solid-state single-frequency continuous-wave lasers are high-quality light sources for fundamental research and application fields， including quantum optics， high-precision measurement， and so on owing to their intrinsic advantages of narrow linewidth， excellent beam quality， high power stability and low noise. With the rapid development of science and technology and the increasing demands of applications， it has become particularly important to scale up the output power of lasers while maintaining their overall performance.However， nonlinear effects become more and more severe with the increase of the output power for fiber lasers， and thermal effects are significantly enhanced under high pump power for rod crystal lasers. To address the limitations of fiber and rod crystal gain media， single-crystal fiber， a novel laser medium that combines the advantages of both， has become a more and more popular research hotspot in the field of all-solid-state lasers due to its excellent physicochemical properties， good thermal management characteristic， pump waveguide effect and high stimulated-Brillouin-scattering threshold. As is well known， scaling up the output power of the single-frequency continuous-wave laser is mainly implemented by means of a laser amplifier or a single resonator. This paper mainly focuses on the research progress of single-frequency continuous-wave lasers based on Nd∶YAG single-crystal fibers. A high-power linearly polarized single-frequency continuous-wave 1 064 nm laser based on the single-crystal fiber master oscillator power amplifier is presented， in which a 140 W low-noise single-frequency continuous-wave laser and an Nd∶YAG single-crystal fiber act as the seed laser and the laser medium of the master oscillator power amplifier， respectively. In order to obtain a high conversion efficiency， the mode-matching efficiency between the pump laser propagated with waveguide form and the freely propagated seed laser is optimized by considering the influence of the degradations of the polarization and the beam quality. When the incident powers of the pump and seed lasers are 262.6 and 126.3 W， respectively， the output power of the linearly polarized single-frequency laser reaches up-to 208 W. To the best of our knowledge， this is the highest output power based on an Nd∶YAG single-crystal fiber master oscillator power amplifier. In addition， a hybrid single-frequency continuous-wave 1 064 nm laser is presented， where both two Nd∶YVO₄ bulk crystals and two Nd∶YAG single-crystal fibers are employed as gain media. By combining the advantages of the good thermal management characteristic of the Nd∶YAG single-crystal fiber with the natural birefringence effect of the Nd∶YVO₄ bulk crystal， a stable single-frequency laser with high output power is achieved. Based on this scheme， a 120 W hybrid single-frequency continuous-wave 1 064 nm laser is obtained by employing Nd∶YAG single-crystal fibers as gain media in a single resonator.The presented laser technologies provide a good reference for achieving high-power single-frequency continuous-wave laser output at different wavelengths based on single-crystal fibers， which will strongly promote the development of laser technology and related fundamental research and application fields.

Key words: laser; single-crystal fiber; single-frequency; continuous-wave; single-crystal fiber amplifier; all-solid-state laser

CLC Number:

TN248.1

WEI Yixiao, SU Jing, LU Huadong, PENG Kunchi. Research Progress of Single-Frequency Continuous-Wave Laser Based on Single-Crystal Fiber[J]. Journal of Synthetic Crystals, 2026, 55(7): 1044-1059.

Figures/Tables 21

Fig.1 Schematic diagram of μ-PD for preparing single-crystal fiber［32］

Fig.2 Schematic diagram of LHPG for preparing single-crystal fiber［37］

Fig.3 Schematic diagram of EFG for preparing single-crystal fiber［41］

Fig.4 Temperature simulations of pumped incident faces of bulk crystals and single-crystal fiber［43］

Fig.5 Laser propagation in single-crystal fiber. （a） Propagation simulation of pump laser［Reprinted］ with permission from ［44］ ? Optical Society of America；（b） transmission schematic diagram of pump laser and signal laser［Adapted］ with permission from ［45］ ? Optical Society of America

Fig.6 Gains for different types of Nd∶YAG laser media［Reprinted］ with permission from ［44］ ? Optical Society of America

Fig.7 Schematic diagram of 60.4 W single-crystal fiber MOPA structure［Reprinted］ with permission from ［50］ ? Optica Publishing Group

Fig.8 Output results of first stage single-crystal fiber MOPA， with inset showing beam profile and beam quality factors after two amplifications［Reprinted］ with permission from ［50］ ? Optica Publishing Group

Fig.9 Output power and extraction efficiency of second stage single-crystal fiber MOPA［Reprinted］ with permission from ［50］ ? Optica Publishing Group

Fig.10 Transverse-mode characteristic of 60.4 W 1 064 nm laser［Reprinted］ with permission from ［50］ ? Optica Publishing Group

Fig.11 Schematic diagram of 208 W single-crystal fiber MOPA structure［Reprinted］ with permission from ［52］ ? Optica Publishing Group

Fig.12 Theoretical calculation results［Reprinted］ with permission from ［52］ ? Optica Publishing Group. （a） Relationship between Mq2 and seed laser waist radius for different incident pump powers；（b） relationship between mode-matching efficiency between pump laser and seed laser in single-crystal fiber and seed laser waist radius for different incident pump powers

Fig.13 Output power of amplifier［Adapted］ with permission from ［52］ ? Optica Publishing Group. （a） Total output power；（b） output power of linearly polarized laser；（c） output power of depolarization laser

Fig.14 Dependence of depolarization coefficient on incident pump power for different seed powers when seed laser waist radius is 200 μm［Adapted］ with permission from ［52］ ? Optica Publishing Group

Fig. 15 Variations of Mq2 and corresponding spatial beam profile with incident pump power when seed laser waist radius is 200 μm［Adapted］ with permission from ［52］ ? Optica Publishing Group

Fig.16 Transverse-mode characteristic of linearly polarized 1 064 nm laser［Adapted］ with permission from ［52］ ? Optica Publishing Group

Fig.17 Schematic diagram of Nd∶YVO4-Nd∶YAG single-crystal fiber hybrid laser structure［Reprinted］ with permission from ［59］ ? Optica Publishing Group

Fig.18 Dependencies of cavity mode sizes at positions of four laser crystals on P1-2 when P3-4 are 90， 120 and 180 W［Reprinted］ with permission from ［59］ ? Optica Publishing Group. （a） Cavity mode sizes at places of Nd1-2；（b） cavity mode sizes at places of SCF1-2

Fig.19 Dependencies of output powers on total incident pump power［Reprinted］ with permission from ［59］ ? Optica Publishing Group

Fig.20 Transverse-mode characteristic of single-frequency 1 064 nm laser［Reprinted］ with permission from ［59］ ? Optica Publishing Group

Table 1 Performance parameters of high power single-frequency continuous-wave 1 064 nm lasers

Year	Gain medium	Implementation method	Power/W	Beam quality factor	Linewidth	Power stability	Reference
2014	Yb-doped photonic crystal fiber	MOPA	811	1.1 or 1.2	<2 MHz	—	［10］
2020	Nd∶YVO₄crystal		195	—	—	—	［23］
2022	Nd∶YAG single-crystal fiber		60.4	M_x²=1.51 M_y²=1.38	16.35 kHz	0.97% （1 h）	［50］
2024	Nd∶YAG single-crystal fiber		208	M_x²=2.29 M_y²=1.92	158 kHz	±1% （5 h）	［52］
2021	Nd∶YAG crystal	Single resonator	55.6	M_x²=1.11 M_y²=1.25	29 MHz	—	［65］
2023	Nd∶YVO₄crystal		140	M_x²=1.23 M_y²=1.21	102 kHz	±1.1% （5 h）	［51］
2025	Nd∶YVO₄-Nd∶YAG single-crystal fiber		120	M_x²=1.34 M_y²=1.35	170 kHz	±0.9% （4 h）	［59］

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