从气体到液体的宽带太赫兹源的研究进展

Research progress on broadband terahertz sources:from gas to liquid

摘要:

近些年，气体(空气等离子体)的太赫兹光子学蓬勃发展，但关于液体在太赫兹波段产生的研究报道相对较少，尤其是液态水，在太赫兹频段表现出显著的吸收性能。因此，长期以来学界普遍认为液体不可能是太赫兹波的来源。最近，通过飞秒激光激发液体产生宽带太赫兹波的实验得到了证实，液体作为太赫兹波辐射源具有独特的特性。液体的密度近似固体，在与激光脉冲的相互作用中表现优异，效果远超气体源。气体和液体的流动性保证每次激光脉冲都能与新的靶材区域接触，极大地避免了介质的损伤或退化，这是固体材料所难以实现的功能。正是这些独特的特性，使气体和液体在高能量密度等离子体的研究及作为下一代太赫兹波源的开发中展现出巨大的潜力。本文回顾了气体和液体作为宽带太赫兹源方面的研究进展，并对比了使用气体和液体生成太赫兹波的多种方法。太赫兹波气体和液体光子学揭示了开发新型太赫兹波源的潜力，并为研究激光与液体间的相互作用开辟了新的研究方向。

Abstract:

In recent years, terahertz photonics of gases (such as air plasma) has developed rapidly, but there are relatively few research reports on the generation of terahertz waves by liquids, especially liquid water, which exhibits significant absorption performance in the terahertz frequency range, leading researchers to believe that liquids cannot be sources of terahertz waves. Recently, experiments have confirmed that broadband terahertz waves can be generated by exciting liquids with femtosecond lasers, and liquids have unique characteristics as terahertz wave radiation sources. The density of liquids is close to that of solids, and they perform excellently in interactions with laser pulses, with effects far exceeding those of gas sources. The fluidity of gases and liquids ensures that each laser pulse can interact with a new target area, greatly avoiding damage or degradation of the medium, a function that is difficult to achieve with solid materials. It is these unique characteristics that make gases and liquids show great potential in the research of high-energy-density plasmas and the development of next-generation terahertz wave sources. This article reviews the research progress of gases and liquids as broadband terahertz sources and compares various methods of generating terahertz waves using gases and liquids. Terahertz gas and liquid photonics reveal the potential for developing new types of terahertz wave sources and open up new research directions for studying the interactions between lasers and liquids.