A new publication from Opto-Electronic Science ; DOI 10.29026/oes.2022.220003 considers terahertz generation from laser-induced plasma.
Terahertz wave, known as T-ray, is sandwiched between the microwave and infrared in the electromagnetic spectrum. It has been widely used in the fields of non-destructive testing, spectroscopy, security inspection, and communication owning to its distinctive features. Instead of using weak fields to observed THz modes, one can also use strong THz field to actively trigger nonlinear THz responses of materials, induce the materials to a new state, rapid phase transitions or even interactions with matters.
With the development of ultrafast optics, laser pulse with high peak power is available. In view of the ability of enduring high peak power of laser pulse, laser-induced plasma is a good candidate and responsible for radiating strong terahertz waves.
The authors of this article review the physics and progress of THz generation from the laser-induced plasmas. The schematic diagram of THz generation from plasma is shown in Fig. 1. A comparison of three scenarios of THz generations is shown in Table 1. In this work, a perspective on the future of THz generation from the laser-induced plasma was discussed, as well as its involved challenges.
Table 1. Comparison of THz generation from laser-induced plasma in air, liquid, and solid.
Gas
Liquid
Solid
Configuration
atmosphere
film, line, droplet
foil, bulk
Laser excitation intensity
nonrelativistic
relativistic
>1 0 18 W/c m 2
Excitation field
one/two-color
one-color
THz field
>100MV/cm
~MV/cm
~0.8GV/cm
Conversion efficiency
2.36%
>0.1%
~0.1%
THz energy
0.185mJ
76μJ
~2.3mJ
THz bandwidth
>50THz
~100THz
<20THz
Geometry
easy
complicated
Laser pulse width
~fs
~ps
fs-ps
Detective THz yield
forward/sideway
forward/sideway/backward
Article reference Sun WF, Wang XK, Zhang Y. Terahertz generation from laser-induced plasma. Opto-Electron Sci 1 , 220003 (2022). doi: 10.29026/oes.2022.220003
Keywords: terahertz generation / ultrafast pulses / laser-induced plasma
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The research interests in the team led by Prof. Yan Zhang in Capital Normal University are focusing on terahertz spectroscopy and imaging, terahertz metamaterial, and strong terahertz generation. With their innovated terahertz focal-plane imaging system, highlighted works on the features of terahertz waves were performed. In terms of metasurface, the research team has proposed its own design algorithm, designed and fabricated metasurface lenses, holograms, wavelength-multiplexing, polarization-multiplexing and other devices in the terahertz band, and developed tunable metasurface devices. The research team has been concerned with strong terahertz generations via plasma, as well as their performances including terahertz spectral modulation, polarization controlling and temporal-spatial characterizing.
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