-
为了获得周期量级的中红外超短脉冲,研究人员对OPA方案进行了多种改进,提出了多种基于OPA的周期量级脉冲直接产生的方法。2011年,日本Riken研究组Eiji J. Takahashi等人提出了双啁啾光参量放大(Dual-chirped Optical Parametric Amplification, DC-OPA)技术[40]。该方法利用带啁啾的宽带泵浦光和信号光,通过精确控制两者相对啁啾与符号,实现了宽光谱闲置光的直接输出,并且能量转化效率也更高,最后经过精密的色散补偿,可以直接获得小于2个光周期的中红外脉冲。2018年,该团队利用皮秒脉冲激光泵浦的DC-OPA技术,分别在1~2 μm获得了100 mJ量级的红外光束[41]和在3.3 μm获得了30 mJ量级的中红外光束[42]。
另一种直接产生周期量级中红外脉冲的方法是频率域OPA(Frequency Domain OPA, FOPA)[43],该技术是用一对光栅和一对凹面镜组成一个4f系统,在傅里叶平面内,肩并肩地放置一系列晶体,这些晶体的最佳相位匹配波长都不相同。这样,这一系列晶体的总的增益带宽是由每个晶体的增益带宽和晶体的数量综合决定的。因此,通过合理设计FOPA参数,可以直接获得宽带大能量的激光脉冲。而且,由于OPA过程发生在光栅对中,所以,FOPA过程不需要额外的展宽器和压缩器。2017年,V. Gruson等人[44]在傅里叶平面内用2块BBO晶体通过240 mJ能量泵浦得到了1.8 μm波段30 mJ、11.6 fs的激光输出。表1[41]列出了基于OPA产生的中红外飞秒激光的不同特性比较。
表 1 OPA、OPCPA、FOPA和DC-OPA产生的中红外飞秒激光的特性[41]
Table 1. Characteristics of OPA, OPCPA, FOPA, and DC-OPA for generating MIR femtosecond laser[41]
OPA FOPA DC-OPA OPCPA Pump duration Transform limit Chirped Chirped Transform limit Pump spectrum Broad Broad Broad Narrow Seed duration Transform limit Transform limit Chirped Chirped Seed spectrum Broad Broad Broad Broad Synchronization Automatic Automatic Automatic Active stabilization Energy scaling Difficult Possible Easy Easy Output pulses Signal and idler Signal Signal and idler Signal and idler Conversion efficiency 30%–40% 14% 30%–40% 10%–30% Highest output energy A few millijoules Dozens of millijoules Hundred millijoules Hundred millijoules and above Few-cycle pulse generation? Yes Yes Yes Yes Preserve CEP stability of seed? Yes No Possible Possible Wavelength tunability Excellent Not reported Excellent Good Compressor Not needed Not needed Most often but not always needed Needed -
目前,常见的脉冲后压缩方案主要为:充气空心光纤[9, 45]、气体腔[11, 46]、成丝[47-48]、块体材料[12]、多薄片级联[10]等方案,表2总结了这几种脉冲后压缩方法的不同特征。
表 2 几种脉冲后压缩技术的特征比较
Table 2. Characteristics comparison of several pulse post-compression techniques
HCF Gas-filled cell Filament Bulk material Thin plates System Complexity Complexity Easy Easy General Medium Gas Gas Plasma Solid Solid Spectrum broadening effect SPM SPM SPM and high-order Kerr/plasma SPM SPM Chirp compensation Needed Needed Normal needed or self-compression Normal needed or self-compression Normal needed or self-compression Maximum energy mJ mJ mJ mJ mJ Efficiency 60% 80% 80% 80% 80% Compressed factor 2-10 2-10 2-10 2-10 2-10 Pulse duration Single cycle Single cycle Single cycle Single cycle Single cycle N2 tunability? Gas and pressure Gas and pressure Gas and pressure No No Nonlinearity increasing? Pressure and HCF length Pressure and number of passed Pressure Bulk thickness Plates number Beam profile Excellent General Excellent General General 充气空心光纤是目前最常用的脉冲后压缩方案,由于空心光纤内部充入了惰性气体,因此电离阈值远高于固体材料,可支持大能量的脉冲传输。另一方面,由于光纤长度非常长,可以大大延长脉冲与气体的作用长度,从而获得超宽带的超连续谱。通过控制空心光纤内的气体种类和气压,可以灵活控制非线性的大小。利用空心光纤的脉冲后压缩方案,Pengfei Wang等人[36]将OPCPA获得的5.5 mJ、4 μm激光脉冲进一步压缩至21.5 fs,能量为2.6 mJ。由于4 μm脉冲是OPA闲置光输出,因此其载波包络相位是被动稳定的,文章对其载波包络相位也进行了测量,为370 mrad。
由于受到增益材料的尺寸以及系统光学元件的损伤阈值的影响,单路OPCPA输出功率的进一步提升受到了限制,需要发展峰值功率提升新方案,而其中一种方法就是多路激光相干合束方案。2021年,Junyu Qian等人[49]将两路OPCPA输出的大能量中红外飞秒激光同步注入充满氪气的空心光纤内,利用空心光纤相干合束压缩技术获得了2.7 mJ、22.9 fs的4 μm的中红外超强超短脉冲输出,实验装置如图6所示。同时,由于空心光纤的模式选择效应,这种方法有效解决了传统相干合束引起的光斑劣化,获得了非常优质的高斯型光斑。该方法可以进一步扩展到4路以及更多路激光合束,为超强超短激光峰值功率的进一步提升提供了一种有效手段。
Beijie Shao等人,将多薄片级联与非线性自压缩相结合,提出了一种新型的周期量级中红外脉冲产生方法[50],在1.9 μm的中心波长下产生了0.52 mJ、20 fs、1 kHz的脉冲直接输出,能量稳定性为0.7%(RMS)。该方法克服超强超短脉冲在材料内部自聚焦而对材料造成的损伤,并且利用相应的材料负色散来精确补偿非线性正色散,不需要任何额外的色散补偿元件,可直接输出周期量级中红外脉冲。表3总结了目前不同波段下中红外超强超短激光的典型参数。截至2018年的中红外超强超短激光发展趋势如图7所示。
表 3 不同波段下中红外超强超短激光的典型参数[12, 32, 35, 37, 42, 44, 51-53]
Table 3. Typical parameters of mid-infrared ultra-intense ultrashort lasers at different wavelengths[12, 32, 35, 37, 42, 44, 51-53]
Wavelength/μm 1.5 1.8 2.2 3.3 3.9 5 10 OPA or OPCPA OPCPA FOPA OPCPA DCOPA OPCPA OPA OPA Crystal KTA BBO BBO MgO:LiNbO3 KTA ZGP BGS Energy 26.5 mJ 30 mJ 250 μJ 31 mJ 20 mJ 3.4 mJ 0.81 µJ Repetition frequency 100 Hz 10 Hz 100 kHz 10 Hz 20 Hz 1 kHz 100 kHz Pulse width/fs 60 11.6 16.5 70 30 89.4 126 Post-compression None None None None Bulk material None None
Research progress of mid-infrared ultra-intense and ultrashort laser (Invited)
-
摘要: 近年来,可调谐中红外新波段超强超短激光的出现与迅速发展,开辟了强场物理领域中迄今仍很少探索过的参量空间,为开拓超强超短激光与物质相互作用的新物理、新效应及新应用提供了新机遇。文中总结了中红外超强超短激光近年来的发展趋势与研究方向。针对光参量放大、光参量啁啾脉冲放大、中红外脉冲后压缩以及中红外新型光场调控技术4个研究方向,较全面地分析各自的国内外研究现状,并对未来中红外超强超短激光的发展趋势进行了展望。Abstract: In recent years, the emergence and rapid development of tunable mid-infrared new-band ultra-intense ultrashort lasers have opened up a parametric space in the field of strong-field physics that has rarely been explored so far, providing new opportunities to explore new physics, new effects and new applications of ultra-intense ultrashort laser-matter interactions. The development trends and research directions of mid-infrared ultra-intense ultrashort lasers in recent years were summarized in this paper. The four research directions of optical parametric amplification, optical parametric chirp pulse amplification, mid-infrared pulse post-compression and new optical field modulation technology in mid-infrared were analyzed in a comprehensive manner, and the future development trend of mid-infrared ultra-intense ultrashort lasers was also prospected.
-
Key words:
- mid-infrared /
- ultra-intense ultrashort laser /
- few-cycle /
- new optical field modulation
-
图 2 (a) 最终输出的中红外光谱,实线为实测实验结果,虚线对应于数值模拟的光谱;(b) 以3.86 μm为中心的实验结果;(c) 信号光能量随波长的变化;(d) 闲置光能量随波长的变化[31]
Figure 2. (a) The final output mid-infrared spectra. The solid lines are measured experimental results, the dash lines correspond the spectra from the numerical simulation; (b) Experimental results centered at 3.86 μm; (c) Signal energy versus wavelength; (d) Idler energy versus wavelength[31]
表 1 OPA、OPCPA、FOPA和DC-OPA产生的中红外飞秒激光的特性[41]
Table 1. Characteristics of OPA, OPCPA, FOPA, and DC-OPA for generating MIR femtosecond laser[41]
OPA FOPA DC-OPA OPCPA Pump duration Transform limit Chirped Chirped Transform limit Pump spectrum Broad Broad Broad Narrow Seed duration Transform limit Transform limit Chirped Chirped Seed spectrum Broad Broad Broad Broad Synchronization Automatic Automatic Automatic Active stabilization Energy scaling Difficult Possible Easy Easy Output pulses Signal and idler Signal Signal and idler Signal and idler Conversion efficiency 30%–40% 14% 30%–40% 10%–30% Highest output energy A few millijoules Dozens of millijoules Hundred millijoules Hundred millijoules and above Few-cycle pulse generation? Yes Yes Yes Yes Preserve CEP stability of seed? Yes No Possible Possible Wavelength tunability Excellent Not reported Excellent Good Compressor Not needed Not needed Most often but not always needed Needed 表 2 几种脉冲后压缩技术的特征比较
Table 2. Characteristics comparison of several pulse post-compression techniques
HCF Gas-filled cell Filament Bulk material Thin plates System Complexity Complexity Easy Easy General Medium Gas Gas Plasma Solid Solid Spectrum broadening effect SPM SPM SPM and high-order Kerr/plasma SPM SPM Chirp compensation Needed Needed Normal needed or self-compression Normal needed or self-compression Normal needed or self-compression Maximum energy mJ mJ mJ mJ mJ Efficiency 60% 80% 80% 80% 80% Compressed factor 2-10 2-10 2-10 2-10 2-10 Pulse duration Single cycle Single cycle Single cycle Single cycle Single cycle N2 tunability? Gas and pressure Gas and pressure Gas and pressure No No Nonlinearity increasing? Pressure and HCF length Pressure and number of passed Pressure Bulk thickness Plates number Beam profile Excellent General Excellent General General 表 3 不同波段下中红外超强超短激光的典型参数[12, 32, 35, 37, 42, 44, 51-53]
Table 3. Typical parameters of mid-infrared ultra-intense ultrashort lasers at different wavelengths[12, 32, 35, 37, 42, 44, 51-53]
Wavelength/μm 1.5 1.8 2.2 3.3 3.9 5 10 OPA or OPCPA OPCPA FOPA OPCPA DCOPA OPCPA OPA OPA Crystal KTA BBO BBO MgO:LiNbO3 KTA ZGP BGS Energy 26.5 mJ 30 mJ 250 μJ 31 mJ 20 mJ 3.4 mJ 0.81 µJ Repetition frequency 100 Hz 10 Hz 100 kHz 10 Hz 20 Hz 1 kHz 100 kHz Pulse width/fs 60 11.6 16.5 70 30 89.4 126 Post-compression None None None None Bulk material None None -
[1] Baer T M, Bigelow N P. 2020 visions (lasers) [J]. Nature, 2010, 463(7277): 26-32. doi: 10.1038/463026a [2] Ke L T, Feng K, Wang W T, et al. Near-GeV electron beams at a few per-mille level from a laser wakefield accelerator via density-tailored plasma [J]. Physical Review Letters, 2021, 126(21): 214801. doi: 10.1103/PhysRevLett.126.214801 [3] Kodama R, Norreys P A, Mima K, et al. Fast heating of ultrahigh-density plasma as a step towards laser fusion ignition [J]. Nature, 2001, 412(6849): 798-802. doi: 10.1038/35090525 [4] Zhong J, Li Y, Wang X, et al. Modelling loop-top X-ray source and reconnection outflows in solar flares with intense lasers [J]. Nature Physics, 2010, 6(12): 984-987. doi: 10.1038/nphys1790 [5] Xu T, Shen B, Xu J, et al. Ultrashort megaelectronvolt positron beam generation based on laser-accelerated electrons [J]. Physics of Plasmas, 2016, 23(3): 033109. doi: 10.1063/1.4943280 [6] Popmintchev T, Chen M C, Popmintchev D, et al. Bright coherent ultrahigh harmonics in the keV x-ray regime from mid-infrared femtosecond lasers [J]. Science, 2012, 336(6086): 1287-1291. doi: 10.1126/science.1218497 [7] Armstrong J A, Bloembergen N, Ducuing J, et al. Interactions between light waves in a nonlinear dielectric [J]. Physical Review, 1962, 127(6): 1918-1939. doi: 10.1103/PhysRev.127.1918 [8] Dubietis A, Jonusauskas G, Piskarskas A. Powerful femtosecond pulse generation by chirped and stretched pulse parametric amplification in BBO crystal [J]. Optics Communications, 1992, 88(4-6): 437-440. doi: 10.1016/0030-4018(92)90070-8 [9] Fan G, Balciunas T, Kanai T, et al. Hollow-core-waveguide compression of multi-millijoule CEP-stable 32 μm pulses [J]. Optica, 2016, 3(12): 1308-1311. doi: 10.1364/OPTICA.3.001308 [10] Lu C H, Tsou Y J, Chen H Y, et al. Generation of intense supercontinuum in condensed media [J]. Optica, 2014, 1(6): 400-406. doi: 10.1364/OPTICA.1.000400 [11] Ueffing M, Reiger S, Kaumanns M, et al. Nonlinear pulse compression in a gas-filled multipass cell [J]. Optics Letters, 2018, 43(9): 2070-2073. doi: 10.1364/OL.43.002070 [12] Shumakova V, Malevich P, Alisauskas S, et al. Multi-millijoule few-cycle mid-infrared pulses through nonlinear self-compression in bulk [J]. Nature Communications, 2016, 7: 12877. doi: 10.1038/ncomms12877 [13] Ebrahim-zadeh M, Sorokina I T. Mid-infrared Coherent Sources and Applications[M]. [S. l.]: Springer, 2008. [14] Dai Y F, Li Y Y, Zou X, et al. High-efficiency broadly tunable Cr: ZnSe single crystal laser pumped by Tm: YLF laser [J]. Laser Physics Letters, 2013, 10(10): 105816. doi: 10.1088/1612-2011/10/10/105816 [15] Sorokina I T. Cr2+-doped II–VI materials for lasers and nonlinear optics [J]. Optical Materials, 2004, 26(4): 395-412. doi: 10.1016/j.optmat.2003.12.025 [16] Yakovlev V S, Ivanov M, Krausz F. Enhanced phase-matching for generation of soft X-ray harmonics and attosecond pulses in atomic gases [J]. Optics Express, 2007, 15(23): 15351-15364. doi: 10.1364/OE.15.015351 [17] Allen L, Beijersbergen M W, Spreeuw R J, et al. Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes [J]. Physical Review A, 1992, 45(11): 8185-8189. doi: 10.1103/PhysRevA.45.8185 [18] Soskin M S, Vasnetsov M V. Singular optics [J]. Progress in Optics, 2001, 42(4): 219-276. [19] Inoue R, Yonehara T, Miyamoto Y, et al. Measuring qutrit-qutrit entanglement of orbital angular momentum states of an atomic ensemble and a photon [J]. Physical Review Letters, 2009, 103(11): 110503. doi: 10.1103/PhysRevLett.103.110503 [20] Mair A, Vaziri A, Weihs G, et al. Entanglement of the orbital angular momentum states of photons [J]. Nature, 2001, 412(6844): 313-316. doi: 10.1038/35085529 [21] Yao A M, Padgett M J. Orbital angular momentum: origins, behavior and applications [J]. Advances in Optics and Photonics, 2011, 3(2): 161-204. doi: 10.1364/AOP.3.000161 [22] Bretschneider S, Eggeling C, Hell S W. Breaking the diffraction barrier in fluorescence microscopy by optical shelving [J]. Physical Review Letters, 2007, 98(21): 218103. doi: 10.1103/PhysRevLett.98.218103 [23] Yan Y, Xie G, Lavery M P, et al. High-capacity millimetre-wave communications with orbital angular momentum multiplexing [J]. Nature Communications, 2014, 5: 4876. doi: 10.1038/ncomms5876 [24] Hernandez-garcia C, Picon A, San Roman J, et al. Attosecond extreme ultraviolet vortices from high-order harmonic generation [J]. Physical Review Letters, 2013, 111(8): 083602. doi: 10.1103/PhysRevLett.111.083602 [25] Rego L, Dorney K M, Brooks N J, et al. Generation of extreme-ultraviolet beams with time-varying orbital angular momentum [J]. Science, 2019, 364(6447): eaaw9486. [26] Brida D, Manzoni C, Cirmi G, et al. Generation of broadband mid-infrared pulses from an optical parametric amplifier [J]. Optics Express, 2007, 15(23): 15035-15040. doi: 10.1364/OE.15.015035 [27] Steinle T, Stenmann A, Hegenbarth R, et al. Watt-level optical parametric amplifier at 42 MHz tunable from 1.35 to 4.5 mum coherently seeded with solitons [J]. Optics Express, 2014, 22(8): 9567-9673. doi: 10.1364/OE.22.009567 [28] Haakestad M W, Arisholm G, Lippert E, et al. High-pulse-energy mid-infrared laser source based on optical parametric amplification in ZnGeP2 [J]. Optics Express, 2008, 16(18): 14263-14273. doi: 10.1364/OE.16.014263 [29] Takahashi E J, Kanai T, Nabekawa Y, et al. 10mJ class femtosecond optical parametric amplifier for generating soft x-ray harmonics [J]. Applied Physics Letters, 2008, 93(4): 041111. doi: 10.1063/1.2960352 [30] Thiré N, Beaulieu S, Cardin V, et al. 10 mJ 5-cycle pulses at 1.8 μm through optical parametric amplification [J]. Applied Physics Letters, 2015, 106(9): 091110. doi: 10.1063/1.4914344 [31] Chen Y, Li Y Y, Li W K, et al. Generation of high beam quality, high-energy and broadband tunable mid-infrared pulse from a KTA optical parametric amplifier [J]. Optics Communications, 2016, 365: 7-13. doi: 10.1016/j.optcom.2015.12.001 [32] Heiner Z, Petrov V, Mero M. Efficient, sub-4-cycle, 1-microm-pumped optical parametric amplifier at 10 microm based on BaGa4S7 [J]. Optics Letters, 2020, 45(20): 5692-5695. doi: 10.1364/OL.403856 [33] Cheng S, Chatterjee G, Tellkamp F, et al. Compact Ho: YLF-pumped ZnGeP2-based optical parametric amplifiers tunable in the molecular fingerprint regime [J]. Optics Letters, 2020, 45(8): 2255-2258. doi: 10.1364/OL.389535 [34] Andriukaitis G, Balciunas T, Allisauskas S, et al. 90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier [J]. Optics Letters, 2011, 36(15): 2755-2757. doi: 10.1364/OL.36.002755 [35] Mitrofanov A V, Voronin A A, Sidorov-biryukov D A, et al. Mid-infrared laser filaments in the atmosphere [J]. Scientific Reports, 2015, 5(1): 8368. doi: 10.1038/srep08368 [36] Wang P F, Li Y Y, Li W K, et al. 2.6 mJ/100 Hz CEP-stable near-single-cycle 4 mum laser based on OPCPA and hollow-core fiber compression [J]. Optics Letters, 2018, 43(9): 2197-2200. doi: 10.1364/OL.43.002197 [37] Wang P F, Shao B J, Su H P, et al. High-repetition-rate, high-peak-power 1450 nm laser source based on optical parametric chirped pulse amplification [J]. High Power Laser Science and Engineering, 2019, 7: e32. doi: 10.1017/hpl.2019.19 [38] Ma J, Wang J, Yuan P, et al. Quasi-parametric amplification of chirped pulses based on a Sm3+-doped yttrium calcium oxyborate crystal [J]. Optica, 2015, 2(11): 1006-1009. doi: 10.1364/OPTICA.2.001006 [39] Wand F, Xie G, Yuan P, et al. Theoretical design of 100-terawatt-level mid-infrared laser [J]. Laser Physics Letters, 2015, 12(7): 075402. doi: 10.1088/1612-2011/12/7/075402 [40] Zhang Q, Takahashi E J, Mucke O D, et al. Dual-chirped optical parametric amplification for generating few hundred mJ infrared pulses [J]. Optics Express, 2011, 19(8): 7190-7212. doi: 10.1364/OE.19.007190 [41] Fu Y, Midorikawa K, Takahashi E J. Towards a petawatt-class few-cycle infrared laser system via dual-chirped optical parametric amplification [J]. Scientific Reports, 2018, 8(1): 7692. doi: 10.1038/s41598-018-25783-0 [42] Fu Y, Xue B, Midorikawa K, et al. TW-scale mid-infrared pulses near 3.3 μm directly generated by dual-chirped optical parametric amplification [J]. Applied Physics Letters, 2018, 112(24): 241105. doi: 10.1063/1.5038414 [43] Schmidt B E, Thire N, Boivin M, et al. Frequency domain optical parametric amplification [J]. Nature Communications, 2014, 5: 3643. doi: 10.1038/ncomms4643 [44] Gruson V, Ernotte G, Lassonde P, et al. 2.5 TW, two-cycle IR laser pulses via frequency domain optical parametric amplification [J]. Optics Express, 2017, 25(22): 27706-27014. doi: 10.1364/OE.25.027706 [45] Schmidt B E, Béjot P, Giguère M, et al. Compression of 1.8 μm laser pulses to sub two optical cycles with bulk material [J]. Applied Physics Letters, 2010, 96(12): 121109. doi: 10.1063/1.3359458 [46] Lavenu L, Natile M, Guichard F, et al. Nonlinear pulse compression based on a gas-filled multipass cell [J]. Optics Letters, 2018, 43(10): 2252-2255. doi: 10.1364/OL.43.002252 [47] Shumakova V, Alisauskas S, Malevich P, et al. Chirp-controlled filamentation and formation of light bullets in the mid-IR [J]. Optics Letters, 2019, 44(9): 2173-2176. doi: 10.1364/OL.44.002173 [48] Mitrofanov A V, Voronin A A, Sidorov-Biryukov D A, et al. Subterawatt few-cycle mid-infrared pulses from a single filament [J]. Optica, 2016, 3(3): 299-302. doi: 10.1364/OPTICA.3.000299 [49] Qian J, Wang P, Peng Y, et al. Pulse combination and compression in hollow-core fiber for few-cycle intense mid-infrared laser generation [J]. Photonics Research, 2021, 9(4): 477-483. doi: 10.1364/PRJ.415794 [50] Shao B, Li Y, Peng Y, et al. 1.9 μm few-cycle pulses based on multi-thin-plate spectral broadening and nonlinear self-compression [J]. IEEE Photonics Journal, 2021, 13(3): 1-8. [51] Von Grafenstein L, Bock M, Ueberschaer D, et al. Multi-millijoule, few-cycle 5 microm OPCPA at 1 kHz repetition rate [J]. Optics Letters, 2020, 45(21): 5998-6001. doi: 10.1364/OL.402562 [52] Pupeikis J, Chevreuil P A, Bigler N, et al. Water window soft X-ray source enabled by a 25 W few-cycle 22 µm OPCPA at 100 kHz [J]. Optica, 2020, 7(2): 168-171. doi: 10.1364/OPTICA.379846 [53] Cardin V, Thiré N, Beaulieu S, et al. 0.42 TW 2-cycle pulses at 1.8 μm via hollow-core fiber compression [J]. Applied Physics Letters, 2015, 107(18): 181101. doi: 10.1063/1.4934861 [54] Gauthier D, Ribic P R, Adhikary G, et al. Tunable orbital angular momentum in high-harmonic generation [J]. Nature Communications, 2017, 8: 14971. doi: 10.1038/ncomms14971 [55] Miyamoto K, Miyagi S, Yamada M, et al. Optical vortex pumped mid-infrared optical parametric oscillator [J]. Optics Express, 2011, 19(13): 12220-12226. doi: 10.1364/OE.19.012220 [56] Yamane K, Toda Y, Morita R. Ultrashort optical-vortex pulse generation in few-cycle regime [J]. Optics Express, 2012, 20(17): 18986-18993. doi: 10.1364/OE.20.018986 [57] Qian J, Peng Y, Li Y, et al. Femtosecond mid-IR optical vortex laser based on optical parametric chirped pulse amplification [J]. Photonics Research, 2020, 8(3): 421-425. doi: 10.1364/PRJ.385190 [58] Zhong H, Liang C, Dai S, et al. Polarization-insensitive, high-gain parametric amplification of radially polarized femtosecond pulses [J]. Optica, 2021, 8(1): 62-69. doi: 10.1364/OPTICA.413328