Figure1. Chamber for experiments of high energy density
physics (left) and experimental observation of energetic electron
beams along the solid target surface (right).

Figure 2. Circled distribution of energetic protons produced
with wire target. From this, electrostatic field around the wire
surface can be determined.

The ultrashort intense laser-plasma interaction has been a rapidly evolving field for last decade, known as high-field physics among many other research frontiers. With ultrahigh laser intensities, many extreme conditions can be produced such as ultrahigh temperature and pressure, super-strong electric and magnetic fields, and ultrashort intense X-ray radiation, etc. The intense laser-plasma interaction is closely related to research on laser inertial confinement fusion and also provides an important and unique platform for the study of high energy density physics. Under the auspices of projects such as the National Natural Science Fund and 863 High-tech program, the high field physics group of CAS Institute of Physics led by academician Prof. Zhang Jie, consisted of professors Wei Zhiyi, Sheng Zhengming, and Li Yutong, has achieved much in the research of new sources of particle and radiation from ultrashort intense laser-plasma interactions. Several valuable findings are listed below:

1) First theoretical proposal for the THz radiation of million watts through linear mode conversion of the laser-plasma wakefield under certain conditions. This is a new method to produce THz radiation with high power, which is suitable for THz radiation applications and study of the physics of THz radiation in the nonlin ear region. The emission also provides a simple way to measure the wakefield produced for particle acceleration (Phys. Rev. Lett. 94, 095003 (2005)).

2) First observation of the well collimated energetic electron beam along the target surface when the intense laser incidents at large angles. The experimental results indicate a novel production mechanism of stable and well-directed energetic electron beams by intense laser pulses. Such an electron beam has potential applications in ultrafast electron diffraction research, production of ultrafast X-ray pulse and injection of electrons into the wakefield accelerator (Phys. Rev. Lett. 96, 165003(2006)).

3) Observation of leading effects of energetic ions by deliberately designed cone-fiber targets. This achievement is important for the high energy density physics for it indicates the possibility of controlling the transport of energetic ions at high flux (Phys. Rev. Lett. 96, 084802(2006)).

4) Proposal of the theory of plasma grating production and application in controlling intense laser pulses. Plasma grating can be produced by the interference between the incident and reflected laser beams in the plasma. Such a plasma grating exhibits large dispersion capability and a non uniform photonic band gap with a monotonically increasing width. It is a powerful method for compression of a positively or negatively chirped pulse because it has a damage threshold 3 magnitude higher than ordinary gratings.

5) Study of the interaction of two light filaments propagating in air. Simulations show that the interaction of the two light filaments displays interesting features such as attraction, fusion, repulsion and spiral propagation, depending on the relative phase shift and the crossing angle between them. This study makes people recognize the effects of multi-filaments on a long and stable channel formation (Phys. Rev. Lett. 96, 025003(2006)).

In the past two years, they have published 5 papers on Phys. Rev. Lett, given more than 20 talks on invitations by international conferences, such as that of laser inertial confinement and fast ignition, and fusion science and applications. They have obtained positive comments from the international community of high energy density physics, and built strong relationship of collaboration with many groups of HEDP in England, Japan and America.

(Quoted from 2007 Annual Report)