液态水辐射源产生太赫兹波的研究进展 
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Significance Terahertz (THz) wave, whose frequency range lying between the infrared wave and microwave, is a section of the electromagnetic spectrum with unique features. Broadly, the THz frequency range covers the spectral region from 0.1 to 30 THz, but researchers universally define 0.1--10 THz as the THz band. Owing to the lack of suitable THz radiation sources and detectors, THz wave, once known as "THz Gap" for ages, became the last segment of the entire electromagnetic spectrum to be fully explored. Nevertheless, the ultrafast optoelectronics technology and microscale semiconductor technology, which received rapid development in the 1980s, made emerging from the previous dilemma possible for researchers in this field. Since then, THz technology has been widely used in scientific research and practical application, such as medical treatment, nondestructive testing, national defense, safety inspection, and communication.
Among various branches of THz technologies, THz photonics undoubtedly earns a place in the current hotspots of the field. However, recently, studies on THz photonics focused more on the linear response of material rather than the nonlinear response, and the absence of suitable THz radiation sources with strong field strength might be to blame for this study status. In China, the 973 Program and several other projects associated with fundamental study supported the study of THz photonics well, unfortunately, the related study work is still focused on linear THz systems. Thus, exploiting the technology for building a more suitable THz radiation source system with stronger THz field strength, along with its optimization, is an essential prerequisite for further expanding the practical area of THz waves.
As the most common liquid in life, water plays an important role in academic research. However, water has not been considered an appropriate THz radiation source for a long time owing to its strong absorption in the THz frequency range. While recently, some groups have experimentally confirmed the feasibility of THz wave generation from water under the excitation of a femtosecond laser, and several theoretical models are proposed for the mechanism of the generation processes. Thus, summarizing the current research progress in this field for the study of THz wave generation from water and other liquids is significant.
Progress Under the efforts of professor Zhang Xicheng and his team, a thin water film (~170 μm) under femtosecond laser’s excitation was historically used for THz wave generation in 2017 (
To weaken the total internal reflection at the flat water-air interface in water film, a water line was used for solving this problem. In 2018, strong THz radiation generated from a water line of 200-μm diameter under the femtosecond laser’s excitation was first reported in the experiment (
Although the phenomenon is similar to air, the explanation for the mechanism of THz generation from water is still under study. While other kinds of nonlinear effects existed during the photoionization process in water and the different ionization mechanisms of these two matters may partially account for this mystery. Currently, the theoretical models to explain the phenomenon of THz generation from water include the dipole array model, ponderomotive-force-induced photocurrent model, unidirectional pulse propagation equation model, and radiation field dynamics model.
Conclusions and Prospect The study on THz generation from liquid water would be beneficial for researchers to better understand the interaction between water and intense lasers, and it serves a significant role in the further study of potential THz radiation sources. Based on these reasons, research progresses on THz generation from liquid water recently, are reviewed in this article, which includes experimental schemes for two liquid water sources, the factors related to the improvement of the generated THz energy, as well as the design ideas for relevant theoretical models. Finally, the prospect of this field based on our understanding and the current study achievements is proposed.
1 引言
太赫兹波是一类在频谱上介于红外光与微波之间的电磁辐射,经过三十余年的发展,在医疗、无损检测、**、通信等领域都获得了广泛的研究与应用[1-2],对于太赫兹光子学领域的研究也进入了一个新的阶段。然而到目前为止,关于太赫兹光子学的研究主要集中在物质材料的线性响应范围内,主要原因可归咎于缺乏合适的强场太赫兹辐射源。因此,寻找更加合适的太赫兹辐射源,扩大太赫兹谱带宽范围、增强脉冲太赫兹波的峰值电场,以实现超宽带强场太赫兹波的产生和探测是目前太赫兹领域的研究热点之一,也是进一步扩大太赫兹波应用领域的前提条件。
作为人类生活与生产中具有不可替代意义的液体,水自身的物理、化学及生物性质研究一直是科研领域的重点之一。而作为一种常见的极性液体,水对太赫兹波段的电磁波具有很大的吸收系数[3],该吸收系数可达到102~103 cm-1量级[4],其中在0.25 THz处为118.01 c
本文围绕近些年来以水为太赫兹辐射源的相关研究成果进行论述,包括几种以水为辐射源的太赫兹产生系统的实验设计思路、以水为辐射源产生太赫兹辐射的机制,及对这一领域未来的展望。
2 基于水膜辐射源产生太赫兹波的实验方案
作为一种潜在的太赫兹辐射源,液态水在太赫兹领域得到更广泛的应用与研究的前提便是解决自身对太赫兹波段吸收系数较大、液体不容易在空间上作为一个稳定的激励对象两大主要问题。对此,Dey等[13]曾在2017年提出了一个利用储存着液体的微型比色皿容器作为飞秒激光激励对象的研究方案,并成功探测到了产生的太赫兹波。应该肯定的是,这一方案作为太赫兹液体辐射源的早期成果具有里程碑式的意义,并且在后续的进一步研究(例如辐射源是一些不容易在常温下储存的液体,如液氮[14-16])中起到了很大的作用。但需要指出的是,这一方案也存在两个明显的问题:一是采用的飞秒激光泵浦源的参数条件相对比较苛刻(重复频率为10 Hz,脉冲中心波长为800 nm,脉宽为48 fs,单脉冲能量达5~50 mJ),并不适宜作为液体太赫兹辐射源的一个普适性范例;二是这项工作中产生和探测到的太赫兹辐射以非相干成分为主,也很难成为理想的相干超宽带超强太赫兹辐射源。由此可见,寻找更加适应于水乃至其他种类的极性液体的激励方案和探测手段对研究液态水产生太赫兹波是十分必要的。
2.1 水膜方案的意义
水膜方案是一种利用金属线引导,在重力驱动下流动的薄水膜(数百微米厚)作为被激励对象产生太赫兹辐射的方案,虽然这一方案在一定条件下可能会伴有X射线等副产品的产生[17],但这种思路也克服了微型容器结构的三个主要问题。1)制备的方法与工艺要容易得多;2)在平行于光路方向上,微型容器的长度(一般在厘米量级)可视为对应的水层长度,但由于液态水对太赫兹波吸收系数较大,因此在这一对应长度下需要很强的泵浦光脉冲才能获得比较明显的太赫兹信号,而水膜的厚度仅在几百微米量级,更好地克服了水对太赫兹波吸收的问题;3)微型容器自身可能会在强激光作用下产生响应信号,而这会对由水产生的原始太赫兹信号造成干扰,进而导致获得的太赫兹信号混乱,与之相对应的水膜则基本不存在这个问题[18-20]。基于以上优势,可以认为这种实验装置对研究液态水作为辐射源产生太赫兹波更具说服力。
2.2 基于单色光激励水膜产生太赫兹波
采用金属线引导、靠重力驱动的自由流动水膜这一研究思路可追溯到2014年Wang等[21]的开创性工作中。他们利用由细金属线引导,依靠重力驱使流动的水膜得到了一个超宽带(0.2~30 THz)的太赫兹时域光谱。虽然这一设计的初衷并未涉及以水为辐射源产生太赫兹波的研究,但这一思路仍在后续的研究中起到了启发性的作用。在2017年张希成教授团队的一项研究成果中,Jin等[22]便首次借鉴这一思路实现了从液态水辐射源中产生太赫兹波,实验装置如
图 1. 将激光束聚焦在铝线引导下,重力作用下流动的水膜上产生太赫兹波的实验装置
Fig. 1. Experimental setup for THz wave generation by tightly focusing the optical laser beam into a wire-guided gravity-driven free-flowing water film
图 2. 水膜处于激光传播方向的不同位置时对应的太赫兹场的测量结果[22]。(a)水膜在不同位置处的太赫兹波形(A在焦点前方,B在焦点附近,C在焦点后方,D无水膜);(b)水膜在焦点附近处的太赫兹波形;(c)频域对比
Fig. 2. Measurement results of the THz fields when the water film is at different places along the direction of laser propagation[22]. (a) THz waveforms when the water film is at different places (A before the focal point, B near the focal point, C after the focal point, D without water film); (b) THz waveforms when the water film is moved near the focal point; (c) comparison in the frequency domain
除此以外,Jin等[22]还对水膜方案下泵浦光脉冲的性质与所获得的太赫兹波能量的关系进行了研究,如
图 3. 不同激光脉冲下的归一化太赫兹能量[22]。(a)脉宽;(b)偏振;(c)光脉冲能量
Fig. 3. Normalized THz energy with different laser pulses[22]. (a) Pulse duration; (b) polarization; (c) pulse energy
需要指出的是,Jin等设计的水膜会在光脉冲能量超过阈值后(>420 μJ)出现破裂问题,因此这一设计无法用于探索更高能量的泵浦光对产生太赫兹波的影响。为解决这一问题,张希成教授团队[7]对水膜的设计进行了改良,他们采用了一个加工过的扁平喷嘴产生的厚度为120 μm的水膜(
图 4. 张希成团队设计的两种不同结构的水膜。(a)金属线引导、靠重力驱动的自由流动水膜;(b)由扁平液体喷嘴产生的水膜[7]
Fig. 4. Two kinds of water films with different structures designed by Zhang Xicheng’s team. (a) Wire-guided gravity-driven free-flowing water film; (b) water film created by a flat liquid nozzle[7]
2.3 基于双色光激励水膜产生太赫兹波
2018年,Jin等[24]使用双色飞秒脉冲激光激励水膜产生了太赫兹波,结构装置如
图 5. 双色光激励水膜产生太赫兹波的实验装置[24]
Fig. 5. Experimental setup for THz wave generation from a water film under two-color laser’s excitation[24]
从不同脉宽的泵浦光产生太赫兹波的效果[24]来看,当泵浦光的脉宽为50 fs时,双色光方案产生的太赫兹波强度大约是单色光方案产生的太赫兹波强度的10倍,但由于电离机制的不同,其提升效果并不如同等条件下的单、双色空气辐射源方案之间的对比明显;而在300 fs条件下,双色光方案产生的太赫兹波强度只比单色光方案的强度提高了11%,这可归咎于基频光与倍频光间存在的不均匀啁啾、相对较宽的脉宽条件下倍频光产生的效率下降,导致双色光能量比例不均。除此以外,对基、倍频光之间的相位差的调制也会对太赫兹辐射能量产生影响。例如从双色光脉冲能量与产生的太赫兹辐射能量的关系上看,如
图 6. 从水膜中产生的太赫兹波能量与激光脉冲(包括ω和2ω)能量的关系曲线[24]
Fig. 6. Relation curve of THz energy generated from water film and laser pulse (including ω and 2ω) energy[24]
3 基于水线辐射源产生太赫兹波的实验方案
3.1 水线方案的意义
水线辐射源方案是另一种激励液态水产生太赫兹波的研究方案,主要设计思路是利用一个内表面抛光处理过(这样可以使形成的水线结构的表面更均匀,结构自身稳定性更高)的注射器针头,配合相应的水循环系统来形成一个直径为几百微米量级的圆柱体水线,并将其作为泵浦光的激励对象,进而产生太赫兹波。
3.2 水线方案的实验设计
2019年,张存林团队[26]首次采用水线辐射源产生了太赫兹波,实验装置如
图 8. 使用水线产生太赫兹波的实验装置,插图是激光与水线相互作用的几何示意图[26]
Fig. 8. Experimental setup for THz wave generation using a water line, the inset means the geometric diagram of the laser interacted with the water line[26]
3.3 影响水线方案产生太赫兹波效率的因素
在水线方案中,太赫兹波的振幅会随泵浦光脉冲能量的增大而呈类似线性关系的增大[26]。对于水线直径的大小和产生的太赫兹辐射强度之间的关系,Gao等[27]认为直径过大的水线对太赫兹辐射总体的吸收较强,不容易探测到明显的太赫兹辐射信号,直径过小的水线则没有足够的接触面积/体积用于实现激光脉冲与水分子之间的相互作用,因此产生的太赫兹信号也不会很强。而张希成教授团队的两项研究则进一步证实了这一结论[25, 28]。如
图 9. 水线直径对水线产生太赫兹波的影响[25]。(a)泵浦光的最佳脉宽;(b)太赫兹波能量
Fig. 9. Effect of the diameter of water line on THz wave generation from a water line[25]. (a) Best pulse duration of the pump beam; (b) THz wave energy
2020年,Feng等[29]对水线方案中泵浦光的光轴方向与太赫兹波探测方向的夹角α[如
图 10. α对水线产生太赫兹波的影响[29]。(a)α的几何示意图;(b)采用不同直径的水线时太赫兹能量与α之间的关系
Fig. 10. Effects of α on THz wave generation from a water line[29]. (a) Geometric diagram of α; (b) relationship between α and THz energy when water lines with different diameters are used
4 液态水产生太赫兹波的理论模型
对于液态水产生太赫兹波的物理解释是进一步理解水分子与强激光、水分子与太赫兹波这两组物质间相互作用的重要组成部分。虽然液态水辐射源产生太赫兹辐射过程的大部分现象与空气辐射源产生太赫兹辐射的过程是相同的,但由于水分子与强激光的相互作用过程中还存在着其他种类的非线性效应(如自聚焦、光强钳制、自陡峭效应和光谱展宽)[30-32],且液态水的光致电离机制也与空气不同(前者主要是多光子电离和级联电离[22],后者以隧穿电离为主[33]),因此对这一现象的解释在该领域尚无定论。目前用于解释液态水产生太赫兹波的物理模型包括偶极子模型[7, 29, 34]、光电流模型[26]、单向脉冲传播方程(UPPE)模型[13]、辐射场动力学模型[23, 35]等。
4.1 偶极子模型
强激光与液态水的相互作用过程会伴随着多光子电离和级联电离现象,由于电离区域内的准自由电子密度呈梯度分布,所以在有质动力的作用下,准自由电子会向电子密度较低的区域移动,而其他质量相对较大的带电粒子则在空间上相对静止。但由于电子的移动速度要比激光脉冲的包络慢,因此在激光传播方向上电离产生的载流子密度始终保持一致,而电子则获得了一个反向的加速度,并在沿激光传播方向产生了一个偶极子,作为一个独立的太赫兹辐射源[36]。在远场观测到的每一个独立偶极子的太赫兹电场强度
式中:J是准自由电子产生的电流的振幅矢量;ΔL是在观测方向上偶极子的长度;ε0是真空中的介电常数;ω0和k分别是泵浦光的角频率和波数;r是观测点与原点(即偶极子中心)之间的距离;θ是以原点为中心的坐标系下观测点方向与激光传播方向之间的夹角。
在这一模型中,众多偶极子沿激光传播方向形成了一个阵列,而产生的太赫兹辐射又是相干的,因此这个阵列产生的太赫兹电场总强度Earray可记为
式中:d表示相邻偶极子之间的距离;m表示偶极子的数量。
考虑到水对太赫兹波的吸收作用,实际耦合出水系统中的太赫兹电场强度还与该系统的太赫兹透过率A有关,从而得出最终的太赫兹电场强度[29]为
4.2 光电流模型
与瞬态光电流模型[37-39]类似,张存林团队[26]将水线中太赫兹波的产生机理归咎于强激光在空气-水线界面上产生了净感应光电流,而这种光电流最终会以太赫兹辐射的形式表现出来。他们认为强激光在水中的传输过程会和空气[40]一样伴随着自聚焦效应的存在和等离子体的产生,并最终导致在激光光轴的两侧形成正、负两个方向的电流。如
图 11. 泵浦光与水线相互作用的几何示意图,Δx表示激光传播轴与水线中心点O'之间的距离[26]。(a)Δx=0;(b)Δx≠0
Fig. 11. Geometric diagram of the pump laser interacted with the water line, while Δx means the distance between laser propagation axis and the center point O' of water line[26]. (a) Δx=0;(b) Δx≠0
4.3 单向脉冲传播方程模型
UPPE模型是一种基于麦克斯韦方程组推导,并用于非线性光脉冲动力学模拟的模型[41-43]。Dey等[13]把水中产生太赫兹辐射归咎于四波混频效应,并借鉴UPPE模型的思路给出了一个适用于液体太赫兹辐射源的UPPE方程:
式中:E是泵浦光脉冲的电场强度矢量;kz是激光的波矢k0在沿激光传播方向(即z轴)上的分量大小;ω是泵浦光的角频率;μ0是真空中的磁导率;PNL是激光在水中传播的三阶非线性效应的极化强度;Jf是由光致电离产生的自由电子运动产生的电流密度;Ja是与激光在水中传输过程中的吸收效应有关的电流密度。
为了进一步解释自由电子电流Jf,Dey等[13]还提出了一个用于描述自由电子密度ρ的动力学方程,用于配套分析UPPE模型:
式中:ρNT是中性原子密度;R1与R2分别表征液态水的光致电离率与雪崩电离率。
在具体的应用上,Dey等[13]将泵浦光脉冲设定为高斯线型,并基于水和酒精的相关参数进行了仿真,仿真结果与实验结果相吻合。
5 结束语
根据前文的介绍与分析,可以发现液态水太赫兹辐射源的研究虽然起步较晚,但相关的实验探索与理论研究已有了令人振奋的成果,相信在未来还会有更多关于这一领域的研究成果问世。从未来的发展角度来看,对液体太赫兹辐射源系统的细节乃至整体的优化、液体-太赫兹辐射之间相互作用的研究依然是这一领域的重要课题。
5.1 液态水辐射源的优化
优化液态水辐射源,乃至开发出新形态的液态水辐射源是尽可能减小液态水对太赫兹波的绝对吸收作用,并使其能在空间上克服无固定形态而成为更合适的太赫兹辐射源的重要一环。例如在目前较为广泛采用的水线与水膜两大方案外,华东师范大学的曾和平团队[44]还提出了一个基于水楔的双色光太赫兹辐射源方案。他们利用水的表面张力,通过重力驱动水从宽度为1 mm的薄板和铝线之间的空隙自然流下而形成一个水楔。与水线方案中曲面的作用相类似,铝线直径与薄板厚度的差异将引起水楔表面张力的不对称性,在减少水-空气边界处的太赫兹全反射现象的同时耦合出相比水膜方案更强的太赫兹辐射。
5.2 泵浦源的优化
对泵浦源的优化工作主要包括寻找泵浦光的最佳脉宽、入射角度,选取单、双色光方案,分配泵浦光能量与探测光能量,乃至选择其他潜在的合适中心波长的飞秒激光作为泵浦源等。此外,相关的研究还有利用双泵浦方案产生太赫兹辐射[45](在总泵浦光能量一定的前提下将泵浦光束分为两束:一束作为预泵浦光电离产生等离子体,产生的等离子体会对作为主泵浦光的另一束光产生的太赫兹辐射进行增强)。
5.3 水分子与太赫兹的相互作用
这一领域的研究热点是水溶液的太赫兹时域光谱、利用强太赫兹辐射研究水分子的极性特征、氢键动力学、溶解特性、太赫兹激励响应等[46]。相关的学术成果有Møller等[47]对液态水的太赫兹吸收光谱的测定、Zalden等[20]对多种液体的太赫兹克尔效应的研究、Zhao等[48]的氢键谐振子模型、Tan等[49]利用强太赫兹脉冲作为探针对液态水等离子体内部的准自由电子随时间演化过程的研究等。
5.4 对其他液体辐射源的探索
在液态水以外,对其他液态物质作为太赫兹辐射源进行相关研究也是未来的一个方向。除了提到的液氮[14-16]外,关于酒精、丙酮、甲醇、α-蒎烯、重水[2, 13, 23, 50]等液体辐射源产生太赫兹波的研究成果已被提出。从这些液体产生太赫兹辐射的效率来看,非极性液体辐射源产生太赫兹波的效率要高于极性液体。
[1] Horiuchi N. Bright terahertz sources[J]. Nature Photonics, 2013, 7(9): 670-671.
[2] JinQ, E YW, Zhang LL, et al. THz aqueous photonics and beyond[C] //2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), September 9-14, 2018, Nagoya, Japan.New York: IEEE Press, 2018: 1- 4.
[3] Vij J K, Simpson D R J, Panarina O E. Far infrared spectroscopy of water at different temperatures: GHz to THz dielectric spectroscopy of water[J]. Journal of Molecular Liquids, 2004, 112(3): 125-135.
[4] 范姝婷, 马莹玉, 舒国响, 等. 太赫兹与水的相互作用: 机理、应用和新趋势[J]. 深圳大学学报(理工版), 2019, 36(2): 200-206.
Fan S T, Ma Y Y, Shu G X, et al. The interaction of terahertz with water molecules: mechanism, applications, and new trends[J]. Journal of Shenzhen University (Science and Engineering), 2019, 36(2): 200-206.
[5] Hale G M, Querry M R. Optical constants of water in the 200-nm to 200-microm wavelength region[J]. Applied Optics, 1973, 12(3): 555-563.
[6] Thrane L, Jacobsen R H, Uhd Jepsen P, et al. THz reflection spectroscopy of liquid water[J]. Chemical Physics Letters, 1995, 240(4): 330-333.
[7] Yiwen E, Jin Q, Tcypkin A, et al. Terahertz wave generation from liquid water films via laser-induced breakdown[J]. Applied Physics Letters, 2018, 113(18): 181103.
[8] Cook G R, Metzger P H. Photoionization and absorption cross sections of O2 and N2 in the 600- to 1000-Å region[J]. The Journal of Chemical Physics, 1964, 41(2): 321-336.
[10] Tcypkin A N, Melnik M V, Zhukova M O, et al. High Kerr nonlinearity of water in THz spectral range[J]. Optics Express, 2019, 27(8): 10419-10425.
[11] Crowell R A, Bartels D M. Multiphoton ionization of liquid water with 3.0--5.0 eV photons[J]. The Journal of Physical Chemistry, 1996, 100(45): 17940-17949.
[12] Nikogosyan D N, Oraevsky A A, Rupasov V I. Two-photon ionization and dissociation of liquid water by powerful laser UV radiation[J]. Chemical Physics, 1983, 77(1): 131-143.
[13] Dey I, Jana K, Fedorov V Y, et al. Highly efficient broadband terahertz generation from ultrashort laser filamentation in liquids[J]. Nature Communications, 2017, 8(1): 1184.
[15] Balakin A V, Garnov S V, Makarov V A, et al. “Terhune-like” transformation of the terahertz polarization ellipse “mutually induced” by three-wave joint propagation in liquid[J]. Optics Letters, 2018, 43(18): 4406-4409.
[16] Yiwen E, Cao Y Q, Ling F, et al. Flowing cryogenic liquid target for terahertz wave generation[J]. AIP Advances, 2020, 10(10): 105119.
[17] Huang H H, Nagashima T, Hsu W H, et al. Dual THz wave and X-ray generation from a water film under femtosecond laser excitation[J]. Nanomaterials, 2018, 8(7): 523.
[18] Bodrov S, Sergeev Y, Murzanev A, et al. Terahertz induced optical birefringence in polar and nonpolar liquids[J]. The Journal of Chemical Physics, 2017, 147(8): 084507.
[19] Penkov N, Shvirst N, Yashin V, et al. Terahertz spectroscopy applied for investigation of water structure[J]. The Journal of Physical Chemistry B, 2015, 119(39): 12664-12670.
[20] Zalden P, Song L, Wu X J, et al. Molecular polarizability anisotropy of liquid water revealed by terahertz-induced transient orientation[J]. Nature Communications, 2018, 9(1): 2142.
[22] Jin Q, Yiwen E, Williams K, et al. Observation of broadband terahertz wave generation from liquid water[J]. Applied Physics Letters, 2017, 111(7): 071103.
[23] Tcypkin A N, Ponomareva E A, Putilin S E, et al. Flat liquid jet as a highly efficient source of terahertz radiation[J]. Optics Express, 2019, 27(11): 15485-15494.
[24] Jin Q, Dai J M, Yiwen E, et al. Terahertz wave emission from a liquid water film under the excitation of asymmetric optical fields[J]. Applied Physics Letters, 2018, 113(26): 261101.
[26] Zhang L L, Wang W M, Wu T, et al. Strong terahertz radiation from a liquid-water line[J]. Physical Review Applied, 2019, 12: 014005.
[27] Gao S H, Jin Q, Yiwen E, et al. Investigation of liquid properties on emitting terahertz wave under ultrashort optical excitation[J]. Proceedings of SPIE, 2019, 11196: 1119609.
[30] Liu W, Petit S, Becker A, et al. Intensity clamping of a femtosecond laser pulse in condensed matter[J]. Optics Communications, 2002, 202(1/2/3): 189-197.
[31] Kandidov V P, Kosareva O G, Golubtsov I S, et al. Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation)[J]. Applied Physics B, 2003, 77(2/3): 149-165.
[32] 王浩若, 张冲, 张宏超, 等. 超短脉冲激光与微小水滴相互作用中电子密度和光场的时空分布[J]. 物理学报, 2017, 66(12): 127801.
Wang H R, Zhang C, Zhang H C, et al. Spatiotemporal distributions of plasma and optical field during the interaction between ultra-short laser pulses and water nanodroplets[J]. Acta Physica Sinica, 2017, 66(12): 127801.
[33] 徐智君. 飞秒激光诱导空气等离子体的实验与应用研究[D]. 天津: 南开大学, 2013: 48.
Xu ZJ. Experimental and applied study of femtosecond laser-induced air plasma[D]. Tianjin: Nankai University, 2013: 48.
[34] Wang H Y, Shen T. Unified theoretical model for both one- and two-color laser excitation of terahertz waves from a liquid[J]. Applied Physics Letters, 2020, 117(13): 131101.
[35] Ponomareva E A, Stumpf S A, Tcypkin A N, et al. Impact of laser-ionized liquid nonlinear characteristics on the efficiency of terahertz wave generation[J]. Optics Letters, 2019, 44(22): 5485-5488.
[36] Hamster H, Sullivan A, Gordon S, et al. Subpicosecond, electromagnetic pulses from intense laser-plasma interaction[J]. Physical Review Letters, 1993, 71(17): 2725-2728.
[37] 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.
[38] 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.
[39] Kim K Y. Generation of coherent terahertz radiation in ultrafast laser-gas interactions[J]. Physics of Plasmas, 2009, 16(5): 056706.
[40] 刘伟伟, 薛嘉云, 苏强, 等. 超快激光成丝现象研究综述[J]. 中国激光, 2020, 47(5): 0500003.
[41] Kolesik M, Moloney J V, Mlejnek M. Unidirectional optical pulse propagation equation[J]. Physical Review Letters, 2002, 89(28): 283902.
[42] Kolesik M, Moloney J V. Nonlinear optical pulse propagation simulation: from Maxwell’s to unidirectional equations[J]. Physical Review E, Statistical, Nonlinear, and Soft Matter Physics, 2004, 70(3): 036604.
[43] Babushkin I, Bergé L. The fundamental solution of the unidirectional pulse propagation equation[J]. Journal of Mathematical Physics, 2014, 55(3): 032903.
[45] Yiwen E, Jin Q, Zhang X C. Enhancement of terahertz emission by a preformed plasma in liquid water[J]. Applied Physics Letters, 2019, 115(10): 101101.
[46] 田野, 郭丝霖, 曾雨珊, 等. 强场太赫兹光源及其物质调控研究[J]. 光子学报, 2020, 49(11): 1149001.
Tian Y, Guo S L, Zeng Y S, et al. High-field terahertz sources and matter manipulation[J]. Acta Photonica Sinica, 2020, 49(11): 1149001.
[47] Møller U, Cooke D G, Tanaka K, et al. Terahertz reflection spectroscopy of Debye relaxation in polar liquids[J]. Journal of the Optical Society of America B, 2009, 26(9): A113-A125.
[48] Zhao H, Tan Y, Zhang L L, et al. Ultrafast hydrogen bond dynamics of liquid water revealed by terahertz-induced transient birefringence[J]. Light: Science & Applications, 2020, 9: 136.
[50] Tcypkin A N, Ponomareva E A, Putilin S E, et al. Concentration dependence of terahertz generation in jets of water and ethanol mixtures[J]. Proceedings of SPIE, 2018, 10826: 1082603.
Article Outline
戴建明, 张祎帆, 陈宇轩, 何宇航, 田震. 液态水辐射源产生太赫兹波的研究进展[J]. 中国激光, 2021, 48(19): 1914001. Jianming Dai, Yifan Zhang, Yuxuan Chen, Yuhang He, Zhen Tian. Research Progress on Terahertz Wave Generation from Liquid Water[J]. Chinese Journal of Lasers, 2021, 48(19): 1914001.
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