高效率三倍频产生355nm皮秒激光的实验研究
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摘要
具有高重复频率、高平均功率的皮秒放大激光在科学研究和工业生产中有着重要的应用,尤其是在脆性材料的加工领域,绿光或紫外皮秒激光具有独特的优势.基于我们研制的平均功率23.2 W、重复频率500 kHz、脉冲宽度13.4 ps的Nd:YVO_4激光器,开展了LBO晶体高效率二倍频与三倍频的研究.通过优化相位匹配和晶体内激光的走离,分别得到了平均功率12.7 W的532 nm二倍频激光和9.25 W的355 nm三倍频激光,相应的光光转换效率分别为54.7%和39.8%.激光器具有结构简单、平均功率高、转换效率高等特点,可以广泛地用于科学研究和工业生产中.
Picosecond laser with high-repetition-rate and high pulse energy is widely favorite in many scientific and industrial applications. Some nonlinear crystals can be used to efficiently convert a near-infrared laser into a green laser or an ultraviolet laser which has a higher photon energy and a smaller focal area. Especially for high-quality and high-speed transparent hard material fabrication, green or ultraviolet picosecond laser has been found to possess unique advantages. In this paper, the experiments on high-efficiency second-harmonicgeneration(SHG) and third-harmonic-generation(THG) by using a home-made all-solid-state picosecond laser amplifier and an LBO crystal are reported.The picosecond laser amplifier consists of a seed source, a regenerative amplifier and a two-stage single-pass amplifier. The seed source is a commercial all-solid-state picosecond oscillator with a pulse duration of 8.3 ps and a repetition rate of 68 MHz. The repetition rate is reduced from 68 MHz to 500 kHz by an electro-optic Pockels cell(PC), and the period doubling bifurcation is minimized by reducing the duration of high voltage in PC. Both the regenerative amplifier and the two-stage single-pass amplifier are pumped by three 30-W continuous-wave fiber-coupled laser diodes. After the regenerative amplifier, the seed laser is amplified to 4.86 W with a repetition rate of 500 kHz at 1064 nm. Then the laser power is increased to 23.2 W by a two-stage single-pass amplifier, and the M2 value of the amplified laser in the X direction and in the Y direction are 1.330 and 1.235, respectively. The final pulse duration is 13.4 ps, which is slightly stretched in the amplification chain compared with the seed pulse duration(8.3 ps).For high-efficiency SHG and THG from near-infrared to green and ultraviolet, we carefully study the optical characteristics of some nonlinear crystals, such as LBO, BBO, BIBO, CLBO, etc., and we find that the LBO crystal, which has a high damage threshold, small walk-off and high nonlinear coefficient, is the best choice for both SHG and THG. Then the parameters of the two crystals for SHG and THG are specially designed according to the phase matching condition, the walk-off and the laser parameter. As a result, a 4-mmlong type-I phase matching LBO with cutting angle of θ = 90° and φ = 11.6° is used for SHG, and a 3-mmlong type-II phase matching LBO with cutting angle of θ = 42.2° and φ = 90° is used for THG. Finally, we realize high-efficiency frequency conversion with SHG power of 12.7 W at 532 nm and THG power of 9.25 W at355 nm. The corresponding optical-optical conversion efficiencies reach 54.7% and 39.6%, respectively.
Picosecond laser with high-repetition-rate and high pulse energy is widely favorite in many scientific and industrial applications. Some nonlinear crystals can be used to efficiently convert a near-infrared laser into a green laser or an ultraviolet laser which has a higher photon energy and a smaller focal area. Especially for high-quality and high-speed transparent hard material fabrication, green or ultraviolet picosecond laser has been found to possess unique advantages. In this paper, the experiments on high-efficiency second-harmonicgeneration(SHG) and third-harmonic-generation(THG) by using a home-made all-solid-state picosecond laser amplifier and an LBO crystal are reported.The picosecond laser amplifier consists of a seed source, a regenerative amplifier and a two-stage single-pass amplifier. The seed source is a commercial all-solid-state picosecond oscillator with a pulse duration of 8.3 ps and a repetition rate of 68 MHz. The repetition rate is reduced from 68 MHz to 500 kHz by an electro-optic Pockels cell(PC), and the period doubling bifurcation is minimized by reducing the duration of high voltage in PC. Both the regenerative amplifier and the two-stage single-pass amplifier are pumped by three 30-W continuous-wave fiber-coupled laser diodes. After the regenerative amplifier, the seed laser is amplified to 4.86 W with a repetition rate of 500 kHz at 1064 nm. Then the laser power is increased to 23.2 W by a two-stage single-pass amplifier, and the M2 value of the amplified laser in the X direction and in the Y direction are 1.330 and 1.235, respectively. The final pulse duration is 13.4 ps, which is slightly stretched in the amplification chain compared with the seed pulse duration(8.3 ps).For high-efficiency SHG and THG from near-infrared to green and ultraviolet, we carefully study the optical characteristics of some nonlinear crystals, such as LBO, BBO, BIBO, CLBO, etc., and we find that the LBO crystal, which has a high damage threshold, small walk-off and high nonlinear coefficient, is the best choice for both SHG and THG. Then the parameters of the two crystals for SHG and THG are specially designed according to the phase matching condition, the walk-off and the laser parameter. As a result, a 4-mmlong type-I phase matching LBO with cutting angle of θ = 90° and φ = 11.6° is used for SHG, and a 3-mmlong type-II phase matching LBO with cutting angle of θ = 42.2° and φ = 90° is used for THG. Finally, we realize high-efficiency frequency conversion with SHG power of 12.7 W at 532 nm and THG power of 9.25 W at355 nm. The corresponding optical-optical conversion efficiencies reach 54.7% and 39.6%, respectively.
引文
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[22] Chen L Y, Bai Z X, Pan Y L, Chen M, Li G 2013 Opt. Eng.52 086107
[2] Wang P, Zhao H, Wang Z H, Li D H, Wei Z Y 2006 Acta Phys. Sin. 55 4161(in Chinese)[王鹏,赵环,王兆华,李德华,魏志义2006物理学报55 4161]
[3] He H J, Jiang J W, Cheng M Y, Song J J, Wang Z H, Fang S B, Wei Z Y 2018 Acta Photon. Sin. 47 0914002(in Chinese)[何会军,蒋建旺,程梦尧,宋贾俊,王兆华,方少波,魏志义2018光子学报47 0914002]
[4] Muhammad N, Whitehead D, Boor A, Oppenlander W, Liu Z, Li L 2012 Appl. Phys. A 106 607
[5] Weck A, Crawford T H R, Wilkinson D S, Haugen H K,Preston J S 2008 Appl. Phys. A 90 537
[6] Zhang F, Duan J, Zeng X Y, Li X Y 2009 Chin. J. Las. 363143(in Chinese)[张菲,段军,曾晓雁,李祥友2009中国激光36 3143]
[7] Rauch T, Delmdahl R, Pfeufer V, Mondry M 2009 Laser Tech. J. 6 20
[8] Norreys P A, Zepf M, Moustaizis S, Fews A P, Zhang J, Lee P, Bakarezos M, Danson C N, Dyson A, Gibbon P, Loukakos P, Neely D, Walsh F N, Wark J S, Dangor A E 1996 Phys.Rev. Lett. 76 1832
[9] Liu J X, Wang W, Wang Z H, LZ G, Zhang Z Y, Wei Z Y2015 Appl. Sci. 5 1590
[10] Offerhaus H L, Godfried H P, Witteman W J 1996 Opt.Commun. 128 61
[11] Drring J, Killi A, Morgner U, Lang A, Lederer M, Kopf D2004 Opt. Express 12 1759
[12] Mao X J, Bi G J, Pang Q S, Zou Y 2013 Chin. J. Las. 381002004(in Chinese)[毛小洁,秘国江,庞庆生,邹跃2013中国激光38 1002004]
[13] Zhu P, Li D J, Liu Q Y, Chen J, Fu S J, Shi P, Du K M,Loosen P 2013 Opt. Lett. 38 4716
[14] Borsutzky A, Briinger R, Huang C H, Wallenstein R 1991Appl. Phys. B 52 55
[15] Ghotbi M, Sun Z, Majchrowski A, Michalski E, Kityk I V,Ebrahim Z M 2006 Appl. Phys. Lett. 89 173124
[16] Ueda K, Orii Y,Takahashi Y, Okada G, Mori Y, Yoshimura M 2016 Opt. Express 24 30465
[17] Guo L, Wang G L, Zhang H B, Cui D F, Wu Y C, Lu L,Zhang J Y, Huang J Y, Xu Z Y 2007 Appl. Phys. B 88 197
[18] Yoshida H, Fujita H, Nakatsuka M, Yoshimura M, Sasaki T,Kamimura T, Yoshida K 2006 Jpn. J. Appl. Phys. 45 766
[19] Wang Z P, Teng B, Du C L, Xu X G, Fu K, Xu G B, Wang J Y, Shao Z S 2003 Acta Phys. Sin. 52 2176(in Chinese)[王正平,滕冰,杜晨林,许心光,傅琨,许贵宝,王继扬,邵宗书2003物理学报52 2176]
[20] Wu Y C, Sasaki T, Nakai S, Yokotani A, Tang H G, Chen CT 1993 Appl. Phys. Lett. 62 2614
[21] Wu B C, Chen N, Chen C T, Deng D Q, Xu Z Y 1989 Opt.Lett. 14 1080
[22] Chen L Y, Bai Z X, Pan Y L, Chen M, Li G 2013 Opt. Eng.52 086107