用于超快束匀滑的动态波前调控新方案
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摘要
提出了利用光克尔效应实现激光束波前动态调控,进而实现焦斑超快束匀滑(ps量级)的方案,其原理是利用抽运光动态改变光克尔介质的折射率分布,以对透射主激光束附加时空耦合的动态波前,进而使激光束在靶面的焦斑散斑产生更加快速、多样的变化,最终实现焦斑的超快束匀滑.当抽运光时间波形为高斯脉冲序列,且以小角度倾斜入射至光克尔介质时,由于抽运光和光克尔介质对主激光附加随时间横向移动的周期性球面相位,且球面相位的幅值随时间不断变化,因而可以同步实现激光束焦面散斑的横向和径向超快速扫动,从而更为有效地改善靶面辐照均匀性.
In inertial confinement facilities, the irradiation uniformity of the lasers is highly required to suppress the laser plasma instabilities. In order to realize the ultrafast smoothing of the focal spot, a novel scheme by using an optical Kerr medium and a high-power pump laser is proposed. The principle of the ultrafast beam smoothing scheme is to change the refractive index of the Kerr medium with the pump laser, which appends a spatiotemporal wavefront to the main laser beam in the beamline. The dynamic wavefront modulation of the main laser beam further makes the speckles within the focal spot redistributed rapidly and complicatedly, which contributes to the smoothing of the focal spot. A Gaussian beam with a temporal profile of a Gaussian pulse train is obliquely incident on the optical Kerr medium at a small angle.As a result, the spherical wavefront of the main laser beam is rapidly changed in the direction perpendicular to the propagation direction of the main laser beam. Thus the transverse and the radial redistribution of the speckles within the focal spot are both generated simultaneously. Comparing with the simple radial smoothing scheme, the spherical phase of the main laser beam always changes perpendicularly to the propagation direction in the novel scheme, and thus achieving a more stable beam smoothing effect. Besides, the phase gradient in the center region of the main laser beam changes greatly over time, making the irradiation uniformity on the focal plane further improved. The optimal deflection angle in the optical Kerr medium of the pump laser is obtained. By controlling the deflection angle of the pump laser,the spatial period of the pump laser in the transverse direction is set to be equal to the waist diameter of the main laser,which is identical with one color cycle in the typical smoothing by spectral dispersion technique. Moreover, a relatively low control precision of the deflection angle of the pump laser is required.
In inertial confinement facilities, the irradiation uniformity of the lasers is highly required to suppress the laser plasma instabilities. In order to realize the ultrafast smoothing of the focal spot, a novel scheme by using an optical Kerr medium and a high-power pump laser is proposed. The principle of the ultrafast beam smoothing scheme is to change the refractive index of the Kerr medium with the pump laser, which appends a spatiotemporal wavefront to the main laser beam in the beamline. The dynamic wavefront modulation of the main laser beam further makes the speckles within the focal spot redistributed rapidly and complicatedly, which contributes to the smoothing of the focal spot. A Gaussian beam with a temporal profile of a Gaussian pulse train is obliquely incident on the optical Kerr medium at a small angle.As a result, the spherical wavefront of the main laser beam is rapidly changed in the direction perpendicular to the propagation direction of the main laser beam. Thus the transverse and the radial redistribution of the speckles within the focal spot are both generated simultaneously. Comparing with the simple radial smoothing scheme, the spherical phase of the main laser beam always changes perpendicularly to the propagation direction in the novel scheme, and thus achieving a more stable beam smoothing effect. Besides, the phase gradient in the center region of the main laser beam changes greatly over time, making the irradiation uniformity on the focal plane further improved. The optimal deflection angle in the optical Kerr medium of the pump laser is obtained. By controlling the deflection angle of the pump laser,the spatial period of the pump laser in the transverse direction is set to be equal to the waist diameter of the main laser,which is identical with one color cycle in the typical smoothing by spectral dispersion technique. Moreover, a relatively low control precision of the deflection angle of the pump laser is required.
引文
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[15]Bowers M W,Burkhart S C,Cohen S J,Erbert G V,Heebner J E,Hermann M R,Jedlovec D 2007 Proc.SPIE 6451 Solid State Lasers XVI:Technology and Devices San Jose,CA,United States,January 20-25,2007p64511
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[18]Li T F,Hou P C,Zhang B 2016 Acta Opt.Sin.36 144(in Chinese)[李腾飞,侯鹏程,张彬2016光学学报36 144]
[19]Zhang R 2013 Ph.D.Dissertation(Hefei:University of Science and Technology of China)(in Chinese)[张锐2013博士学位论文(合肥:中国科学技术大学)]
[20]Skupsky S,Short R W,Kessler T J,Craxton R S,Letzring S,Soures J M 1989 J.Appl.Phys.66 3456
[21]Rothenberg J E 1997 JOSA B 14 1664
[2]Meyerhofer D D,Delettrez J A,Epstein R,Glebov V Y,Goncharov V N,Keck R L,Mc Crory R L,Mc Kenty PW,Marshall F J,Radha P B,Regan S P,Roberts S,Seka W,Skupsky S,Smalyuk V A,Sorce C,Stoeckl C,Soures J M,Town R P J,Yaakobi B,Zuegel J D 2001Phys.Plasmas 8 2251
[3]Wen S L,Yan H,Zhang Y H,Yang C L,Wang J,Shi QK 2014 Acta Opt.Sin.34 162(in Chinese)[温圣林,颜浩,张远航,杨春林,王健,石琦凯2014光学学报34 162]
[4]Jiang X J,Zhou S L,Lin Z Q 2007 Chin.J.Laser 111533(in Chinese)[江秀娟,周申蕾,林尊琪2007中国激光11 1533]
[5]Li P,Wang W,Zhao R C,Geng Y C,Jia H T,Su JQ 2014 Acta Phys.Sin.63 215202(in Chinese)[李平,王伟,赵润昌,耿远超,贾怀庭,粟敬钦2014物理学报63215202]
[6]Lehmberg R H,Schmitt A J,Bodner S E 1987 J.Appl.Phys.62 2680
[7]Regan S P,Marozas J A,Craxton R S,Kelly J H,Donaldson W R,Jaanimagi P A,Jacobs-Perkins D,Keck RL,Kessler T J,Meyerhofer D D,Sangster T C,Seka W,Smalyuk V A,Skupsky S,Zuegel J D 2005 J.Opt.Soc.Am.B 22 998
[8]Berger R L,Lefebvre E,Langdon A B,Rothenberg J E,Still C H,Williams E A 1999 Phys.Plasmas 6 1043
[9]Yahia V,Masson-Laborde P E,Depierreux S,Goyon C,Loisel G,Baccou C,Borisenko N G,Orekhov A,Rienecker T,Rosmej O,TeychennéD,Labaune C 2015Phys.Plasmas 22 042707
[10]Couris S,Renard M,Faucher O,Lavorel B,Chaux R,Koudoumas E,Michaut X 2003 Chem.Phys.Lett.369318
[11]Zhong Z Q,Hou P C,Zhang B 2015 Opt.Lett.40 5850
[12]Hou P C,Zhong Z Q,Zhang B 2016 Opt.Laser Technol.85 48
[13]Haynam C A,Wegner P J,Auerbach J M,Bowers MW,Dixit S N,Erbert G V,Heestand G M,Henesian MA,Hermann M R,Jancaitis K S,Manes K R,Marshall C D,Mehta N C,Menapace J,Moses E,Murray J R,Nostrand M C,Orth C D,Patterson R,Sacks R A,Shaw M J,Spaeth M,Sutton S B,Williams W H,Widmayer C C,White R K,Yang S T,van Wonterghem B M 2007Appl.Opt.46 3276
[14]Zeng S G,Hu J,Wang F 2013 Acta Opt.Sin.33 156(in Chinese)[曾曙光,胡静,王飞2013光学学报33 156]
[15]Bowers M W,Burkhart S C,Cohen S J,Erbert G V,Heebner J E,Hermann M R,Jedlovec D 2007 Proc.SPIE 6451 Solid State Lasers XVI:Technology and Devices San Jose,CA,United States,January 20-25,2007p64511
[16]Henesian M A,Haney S W,Thomas M,Trenholme J B1997 Solid State Lasers for Application to Inertial Confinement Fusion:Second Annual International Conference Paris,France,October 22-25,1996 p783
[17]Kedenburg S,Steinmann A,Hegenbarth R,Steinle T,Giessen H 2014 J.Appl.Phys.117 803
[18]Li T F,Hou P C,Zhang B 2016 Acta Opt.Sin.36 144(in Chinese)[李腾飞,侯鹏程,张彬2016光学学报36 144]
[19]Zhang R 2013 Ph.D.Dissertation(Hefei:University of Science and Technology of China)(in Chinese)[张锐2013博士学位论文(合肥:中国科学技术大学)]
[20]Skupsky S,Short R W,Kessler T J,Craxton R S,Letzring S,Soures J M 1989 J.Appl.Phys.66 3456
[21]Rothenberg J E 1997 JOSA B 14 1664