基于光丝阵列的太赫兹辐射增强方法
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摘要
基于飞秒激光光丝阵列,从实验上实现了太赫兹(THz)辐射的增强。结果表明,使用阶跃型相位板产生光丝阵列,在相同飞秒脉冲能量下,相比于单光丝情况,光丝阵列辐射THz信号强度被增强,且THz信号强度与光丝数目成正比。当入射能量为5.8 mJ时,8根光丝时辐射的THz能量为31.73 nJ,辐射效率为5.47×10~(-6)。所提方法有望解决飞秒激光辐射THz过程中的能量饱和问题。
In this study, we experimentally demonstrated the enhancement of a terahertz(THz) signal generated by a femtosecond laser-filament array in air using a simple experimental setup in which a step phase plate is used to generate multiple parallel filaments. The results show that at a given incident-femtosecond-pulse energy, compared with the case of single filament, the proposed method enhances the THz radiation intensity, and the THz radiation intensity is proportional to the number of filaments. Further, at an incident energy of 5.8 mJ, the THz energy generated by eight filaments is 31.73 nJ and the radiation efficiency is 5.47×10~(-6). This simple method can be used to solve the energy saturation problem in the generation of THz radiation through femtosecond laser filamentation in air.
In this study, we experimentally demonstrated the enhancement of a terahertz(THz) signal generated by a femtosecond laser-filament array in air using a simple experimental setup in which a step phase plate is used to generate multiple parallel filaments. The results show that at a given incident-femtosecond-pulse energy, compared with the case of single filament, the proposed method enhances the THz radiation intensity, and the THz radiation intensity is proportional to the number of filaments. Further, at an incident energy of 5.8 mJ, the THz energy generated by eight filaments is 31.73 nJ and the radiation efficiency is 5.47×10~(-6). This simple method can be used to solve the energy saturation problem in the generation of THz radiation through femtosecond laser filamentation in air.
引文
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[12] L?ffler T,Jacob F,Roskos H G.Generation of terahertz pulses by photoionization of electrically biased air[J].Applied Physics Letters,2000,77(3):453-455.
[13] Bhasin L,Tripathi V K.Terahertz generation from laser filaments in the presence of a static electric field in a plasma[J].Physics of Plasmas,2011,18(12):123106.
[14] Houard A,Liu Y,Prade B,et al.Strong enhancement of terahertz radiation from laser filaments in air by a static electric field[J].Physical Review Letters,2008,100(25):255006.
[15] Chen Y P,Wang T J,Marceau C,et al.Characterization of terahertz emission from a DC-biased filament in air[J].Applied Physics Letters,2009,95(10):101101.
[16] Liu Y,Houard A,Prade B,et al.Terahertz radiation source in air based on bifilamentation of femtosecond laser pulses[J].Physical Review Letters,2007,99(13):135002.
[17] Xie X,Xu J Z,Dai J M,et al.Enhancement of terahertz wave generation from laser induced plasma[J].Applied Physics Letters,2007,90(14):141104.
[18] Tzortzakis S,Méchain G,Patalano G,et al.Coherent subterahertz radiation from femtosecond infrared filaments in air[J].Optics Letters,2002,27(21):1944-1946.
[19] Durand M,Liu Y,Houard A,et al.Fine control of terahertz radiation from filamentation by molecular lensing in air[J].Optics Letters,2010,35(10):1710-1712.
[20] Gao H,Chu W,Yu G L,et al.Femtosecond laser filament array generated with step phase plate in air[J].Optics Express,2013,21(4):4612-4622.
[21] Marburger J H.Self-focusing:theory[J].Progress in Quantum Electronics,1975,4:35-110.
[22] Ak?zbek N,Scalora M,Bowden C M,et al.White-light continuum generation and filamentation during the propagation of ultra-short laser pulses in air[J].Optics Communications,2001,191:353-362.
[23] Brodeur A,Chin S L.Ultrafast white-light continuum generation and self-focusing in transparent condensed media[J].Journal of the Optical Society of America B,1999,16(4):637-650.
[24] Kim K Y,Glownia J H,Taylor A J,et al.Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields[J].Optics Express,2007,15(8):4577-4584.
[2] Roskos H G,Thomson M D,Kre? M,et al.Broadband THz emission from gas plasmas induced by femtosecond optical pulses:from fundamentals to applications[J].Laser & Photonics Reviews,2007,1(4):349-368.
[3] D′Amico C,Houard A,Franco M,et al.Conical forward THz emission from femtosecond-laser-beam filamentation in air[J].Physical Review Letters,2007,98(23):235002.
[4] Zhang Y,Chen Y,Marceau C,et al.Non-radially polarized THz pulse emitted from femtosecond laser filament in air[J].Optics Express,2008,16(20):15483-15488.
[5] Kim K Y,Taylor A J,Glownia J H,et al.Coherent control of terahertz supercontinuum generation in ultrafast laser-gas interactions[J].Nature Photonics,2008,2(10):605-609.
[6] Liu J L,Dai J M,Chin S L,et al.Broadband terahertz wave remote sensing using coherent manipulation of fluorescence from asymmetrically ionized gases[J].Nature Photonics,2010,4(9):627-631.
[7] Sheng Z M,Mima K,Zhang J,et al.Emission of electromagnetic pulses from laser wakefields through linear mode conversion[J].Physical Review Letters,2005,94(9):095003.
[8] Bai Y,Song L W,Xu R J,et al.Waveform-controlled terahertz radiation from the air filament produced by few-cycle laser pulses[J].Physical Review Letters,2012,108(25):255004.
[9] Dai J M,Xie X,Zhang X C.Detection of broadband terahertz waves with a laser-induced plasma in gases[J].Physical Review Letters,2006,97(10):103903.
[10] Massaouti M,Tzortzakis S.Controlling laser filamentation induced strong THz fields[J].Chinese Journal of Physics,2014,52(1):490-503.
[11] Oh T I,Yoo Y J,You Y S,et al.Generation of strong terahertz fields exceeding 8 MV/cm at 1 kHz and real-time beam profiling[J].Applied Physics Letters,2014,105(4):041103.
[12] L?ffler T,Jacob F,Roskos H G.Generation of terahertz pulses by photoionization of electrically biased air[J].Applied Physics Letters,2000,77(3):453-455.
[13] Bhasin L,Tripathi V K.Terahertz generation from laser filaments in the presence of a static electric field in a plasma[J].Physics of Plasmas,2011,18(12):123106.
[14] Houard A,Liu Y,Prade B,et al.Strong enhancement of terahertz radiation from laser filaments in air by a static electric field[J].Physical Review Letters,2008,100(25):255006.
[15] Chen Y P,Wang T J,Marceau C,et al.Characterization of terahertz emission from a DC-biased filament in air[J].Applied Physics Letters,2009,95(10):101101.
[16] Liu Y,Houard A,Prade B,et al.Terahertz radiation source in air based on bifilamentation of femtosecond laser pulses[J].Physical Review Letters,2007,99(13):135002.
[17] Xie X,Xu J Z,Dai J M,et al.Enhancement of terahertz wave generation from laser induced plasma[J].Applied Physics Letters,2007,90(14):141104.
[18] Tzortzakis S,Méchain G,Patalano G,et al.Coherent subterahertz radiation from femtosecond infrared filaments in air[J].Optics Letters,2002,27(21):1944-1946.
[19] Durand M,Liu Y,Houard A,et al.Fine control of terahertz radiation from filamentation by molecular lensing in air[J].Optics Letters,2010,35(10):1710-1712.
[20] Gao H,Chu W,Yu G L,et al.Femtosecond laser filament array generated with step phase plate in air[J].Optics Express,2013,21(4):4612-4622.
[21] Marburger J H.Self-focusing:theory[J].Progress in Quantum Electronics,1975,4:35-110.
[22] Ak?zbek N,Scalora M,Bowden C M,et al.White-light continuum generation and filamentation during the propagation of ultra-short laser pulses in air[J].Optics Communications,2001,191:353-362.
[23] Brodeur A,Chin S L.Ultrafast white-light continuum generation and self-focusing in transparent condensed media[J].Journal of the Optical Society of America B,1999,16(4):637-650.
[24] Kim K Y,Glownia J H,Taylor A J,et al.Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields[J].Optics Express,2007,15(8):4577-4584.