Plasma-based terahertz wave photonics in gas and liquid phases

Abstract

Ultra-broadband, intense, coherent terahertz (THz) radiation can be generated, detected, and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector, with a frequency coverage spanning across and beyond the whole "THz gap." Such a research topic is termed "plasma-based THz wave photonics in gas and liquid phases." In this paper, we review the most important experimental and theoretical works of the topic in the non-relativistic region with pump laser intensity below 10 18 W∕cm 2 .

Optical damage thresholds of single-mode fiber-tip spintronic terahertz emitters

“…Over the last decades, a variety of different terahertz emitters have been developed. A useful classification divides them into two main classes: (1) those based on off-resonant charge motion within nonlinear media of broken inversion symmetry ("optical rectification") [1,2] such as inorganic crystals [3] or suitable organic materials [4], and (2) those based on resonantly induced photocurrents such as photoconductive antennas [5][6][7][8], laser-ionized gases and liquids [9][10][11][12][13], or the recently developed spintronic terahertz emitters (STEs) [14][15][16][17][18].…”

Why do terahertz waves generated from long two-color filament always peak at around 1 THz?

“…5 Recently, some review papers have discussed comprehensively the state-of-the-art advances of this field. 6,7 However, the lack of the frequency selecting and tuning methods for this source impedes its wider application. Some efforts have been made to achieve the frequency tunable THz source, for instance, by using two filaments 8,9 or adding the external cavity.…”

Making and breaking terahertz waves with fluid plasmas

“…Although discovered within a similar period to other solid-state THz generation and detection methods [8] , this approach suffered a much slower pace of development until the finding of substantially increased efficiencies in air plasma via two-color laser excitation [9] . After discussing a suite of experimental and theoretical works and the state of the art in THz gas plasma research, the authors proceed to review plasma-based THz generation and detection in liquids [7] (e.g., water), which has only recently emerged in the past several years [10] but with rapid progress that has stimulated exciting new research directions.…”

“…A prominent solution to this problem has been to use laser-induced plasma in gases (such as air, normalN2, and noble gases) wherein phonon-related absorption and dispersion can be avoided. In their new review paper [7] , Chen et al provide a detailed look at developments in ultrafast THz wave generation, detection, and manipulation over the past three decades in laser-induced gas plasma. Although discovered within a similar period to other solid-state THz generation and detection methods [8] , this approach suffered a much slower pace of development until the finding of substantially increased efficiencies in air plasma via two-color laser excitation [9] .…”