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The search for suitable saturable absorption materials for the 2.79-μm wavelength range has been a key focus in the development of passive Q -switched laser technology at this wavelength. High-purity ethanol serving as a saturable absorber operating within its intrinsic absorption darkening region is comprehensively investigated in this work. Ethanol stands out due to its high damage threshold, excellent fluidity, and long-term chemical stability, thereby making it a promising candidate for mid-infrared applications. Using a custom-designed micrometer-precision liquid cell, the ethanol layer thickness is continuously modulated from 14 μm to 55 μm (±1 μm accuracy), and passive Q -switching can be achieved without the need for an external modulator. The laser system adopts a 248-mm planar resonator, which includes a $\varPhi $3 mm × 70 mm Er, Cr:YSGG rod (Cr3+ 3% (atomic percentage), Er3+ 30% (atomic percentage)), and a flashlamp pumped at 250 μs and 20 Hz. Under these conditions, the output pulse characteristics are governed almost entirely by the ethanol thickness. When the pump energy is fixed at 12.86 J, reducing the layer thickness from 55 μm to 14 μm will shorten the pulse duration from 366.1 ns to 257.9 ns and increase the single-pulse energy from 1.25 mJ to 3.48 mJ. Optimal performance, characterized by 287.6 ns pulses and 11.64 mJ energy, is achieved at a thickness of 45 μm. While maintaining this optimal thickness, increasing the pump energy from 7.01 J to 10.75 J will further compress the pulses from 629.1 ns to 287.6 ns and increases the output energy from 0.52 mJ to 11.64 mJ, none of which do not cause optical damage, indicating a damage threshold exceeding 10 J/cm2. At pump energies exceeding 8.4 J, the ethanol undergoes re-bleaching within its ~20 μs recovery time, resulting in the formation of 2–5 equally spaced nanosecond sub-pulses (6–12 μs spacing, effective repetition ≈ 100 kHz) within a single pump envelope, which is an operating regime highly favorable for precision laser ablation. The beam quality at maximum output is measured to be $ M_x^2 =7.51 $ and $ M_y^2 =7.51 $. These results are supported by rate-equation modeling combined with temperature-dependent absorption cross-sections from the HITRAN database, establishing ethanol as an adjustable, high-damage-threshold liquid saturable absorber for compact mid-infrared Q -switched lasers, and emphasizing the broader potential of hydroxyl-containing liquids for next-generation medical and spectroscopic applications. -
Keywords:
- solid-state lasers /
- Er /
- Cr:YSGG laser /
- passive Q-switching /
- saturable absorber
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Dai C S, Dong Z P, Lin J Q, Yao P J, Xu L X, Gu C 2022 Acta Phys. Sin. 71 174202
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图 1 不同泵浦功率下, 光子数密度随时间变化仿真结果
Figure 1. Simulation results of photon number density changing with time under different pump power.
图 2 Er, Cr:YSGG被动调Q激光实验装置图
Figure 2. Schematic diagram of a passively Q -switched Er, Cr:YSGG laser.
图 3 微米级液体厚度调控装置实物图
Figure 3. Photograph of the micron-scale liquid thickness control device.
图 4 乙醇吸收光谱
Figure 4. Absorption spectrum of ethanol.
图 5 泵浦能量12.86 J、重复频率20 Hz时静态输出脉冲波形图
Figure 5. Static output pulse waveform at a pump energy of 12.86 J and a repetition rate of 20 Hz.
图 6 输出能量和脉冲宽度随溶液厚度的变化
Figure 6. Output energy and pulse duration as a function of thickness of the ethanol.
图 7 乙醇溶液厚度14 μm、泵浦能量12.86 J、重复频率20 Hz时调Q输出脉冲波形图
Figure 7. Pulse waveform of ethanol Q -switched output with ethanol thickness of 14 μm, pump energy of 12.86 J, and repetition rate of 20 Hz.
图 8 输出能量和脉冲宽度随泵浦能量的变化
Figure 8. Output energy and pulse duration as a function of pump energy.
图 9 输出激光光斑和光束质量
Figure 9. Beam profile and beam quality of the laser.
图 10 不同泵浦能量下的脉冲波形图
Figure 10. Pulse waveforms under different pump energies.
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[1] Burikov S, Dolenko T, Patsaeva S, Starokurov Y, Yuzhakov V 2010 Mol. Phys. 108 2427
Google Scholar
[2] Wei C, Zhu X S, Norwood R A, Song F, Peyghambarian N 2013 Opt. Express 21 29488
Google Scholar
[3] Skorczakowski M, Swiderski J, Pichola W, Nyga P, Zajac A, Maciejewska M, Galecki L, Kasprzak J, Gross S, Heinrich A, Bragagna T 2010 Laser Phys. Lett. 7 498
Google Scholar
[4] Wang L, Wang J T, Yang J W, Wu X Y, Sun D L, Yin S T, Jiang H H, Wang J Y, Xu C Q 2013 Opt. Lett. 38 2150
Google Scholar
[5] Yang J W, Wang L, Wu X Y, Cheng T T, Jiang H H 2014 Opt. Express 22 15686
Google Scholar
[6] Huang L, Wang P, Wang Y, Cheng T, Wang L, Jiang H 2024 Photonics 11 432
Google Scholar
[7] Cui Q Z, Wei M G, Xiong Z D, et al. 2019 Infrared Phys. Technol. 98 256
Google Scholar
[8] Huang L, Wang Y Z, Zhang Y Y, Cheng T Q, Wang L, Jiang H H 2024 Opt. Laser Technol. 175 110743
Google Scholar
[9] Wang S W, Tang Y L, Yang J L, Zhong H Z, Fan D Y 2019 Laser Phys. 29 025101
Google Scholar
[10] Tang P H, Wu M, Wang Q K, Miao L L, Huang B, Liu J, Zhao C, Wen S 2016 IEEE Photonics Technol. Lett. 28 1573
Google Scholar
[11] Xiong Z D, Jiang L L, Cheng T Q, Jiang H H 2022 Infrared Phys. Technol. 122 104087
Google Scholar
[12] Li C, Liu J, Jiang S Z, Xu S C, Ma W W, Wang J Y, Xu X D, Su L B 2016 Opt. Mater. Express 6 1570
Google Scholar
[13] Qin Z P, Xie G Q, Ma J G, Yuan P, Qian L J 2018 Photonics Res. 6 1074
Google Scholar
[14] Vodopyanov K L, Shori R, Stafsudd O M 1998 Appl. Phys. Lett. 72 2211
Google Scholar
[15] Deàk J C, Rhea S T, Iwaki L K, Dlott D D 2000 J. Phys. Chem. A 104 4866
Google Scholar
[16] Flór M, Wilkins D M, De La Puente M, Laage D, Cassone G, Hassanali A, Roke S 2024 Science 386 eads4369
Google Scholar
[17] Vodop’yanov K L, Kulevskiǐ L, Pashinin P, Prokhorov A 1982 J. Exp. Theor. Phys. 55 1049
[18] Vodop’yanov L 1990 J. Exp. Theor. Phys. 70 114
[19] Shori R K, Walston A A, Stafsudd O M, Fried D, Walsh J T 2001 IEEE J. Sel. Top. Quantum Electron. 7 959
Google Scholar
[20] Dong J 2003 Opt. Commun. 226 337
Google Scholar
[21] Kucherov A N 2003 Dokl. Phys. 48 90
Google Scholar
[22] Vogel A, Venugopalan V 2003 Chem. Rev. 103 577
Google Scholar
[23] Xian T H, Zhan L, Gao L R, Zhang W Y, Zhang W C 2019 Opt. Lett. 44 863
Google Scholar
[24] 戴川生, 董志鹏, 林加强, 姚培军, 许立新, 顾春 2022 物理学报 71 174202
Google Scholar
Dai C S, Dong Z P, Lin J Q, Yao P J, Xu L X, Gu C 2022 Acta Phys. Sin. 71 174202
Google Scholar
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