Researcher Li Yutong, Institute of Physics, Chinese Academy of Sciences, and Prof. Jie Zhang / Prof. Sheng Zhengming, Shanghai Jiaotong University, and other researchers used the theory of relativistic femtosecond laser and solid film target to obtain large energy coherent terahertz pulses and put forward specific crossover The physical image of radiation.

THz radiation has important applications in materials science, biomedical and defense safety due to its unique single photon energy and "fingerprinting" spectrum. However, the lack of large-energy terahertz radiation source severely limits the development and application of terahertz technology.

At present, the peak power of super-laser reaches up to hundred watts or even wattage, and the focused light intensity exceeds 1018 W / cm2, entering the category of relativity (electrons can be accelerated to the speed of light by the light field). The use of relativistic laser-plasma interaction can effectively generate terahertz pulses, which provides a new platform for the realization of intense terahertz radiation.

Researcher Li Yutong, Institute of Physics, Chinese Academy of Sciences, and Prof. Jie Zhang / Prof. Sheng Zhengming, Shanghai Jiaotong University, and others made a research on new ways of generating terahertz radiation in the relativistic laser-solid target interaction and obtained a Series of groundbreaking results. Recently, the team used a relativistic femtosecond laser with a solid film target to obtain a terahertz pulse with a single shot energy of nearly 400 micro-Joules after the target, which is comparable to the terahertz pulse energy produced by a conventional large accelerator. Relevant findings are published in Phys. Rev. Lett. [116, 205003 (2016)] and edited as Editors' Suggestion.

Schematic diagram of terahertz radiation generated after the laser and solid film target effect on the target

In response to the experimental results, the team proposed a physical image of terahertz radiation: the relativistic laser-plasma interaction produces a large amount of forward superheated electrons that trigger the transition as the electrons escape from the back surface of the target into the vacuum The more radiation produces a terahertz pulse. Since the pulse length of the electron beam is on the order of tens of femtoseconds to picoseconds, the transition radiation is coherent in the terahertz band.

The experimental study of the team compared the transversal radiation radiation of different target types such as metal target, metal-polyethylene target with lateral dimension and thickness. The experimental results are in good agreement with the above physical images.

The terahertz radiation generation mechanism and experimental demonstration proposed by the team open up new avenues for miniaturization, high energy and broad-spectrum terahertz radiation sources. This experimental idea is also expected to be developed into an on-line diagnosis of laser plasma interaction new method.

After the publication of this article, Nature Photonics, Physics World and other famous foreign academic journals and scientific media covered the work.

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