Coherent transition radiation from thin targets irradiated by high intensity laser pulses

• Transition radiations from foil targets irradiated by intense lasers are calculated.
• Spectral shifts of CTR are determined depending on the target expansions.
• Temporal modulation and coherence of hot electron beam are investigated.
• Physical insights into the target expansion and the fast electron transport are obtained.

A theoretical examination on coherent transition radiations (CTR) from the surface of thin solid density target irradiated by high intensity laser is presented. The theory is extended to consider the expansion dynamics of thin foils. The motion of target surfaces leads to the modulation on the temporal structure of micro bunches in the electron beam as well as the spectrum of CTR. The spectral shifts of radiation are owing to the enhancement of electron bunch separation and the relativistic Doppler effects. The radiation power distribution is strongly affected by the temporal coherence of electron beam structure, so thus the electron temperature and velocity dispersions. With these effects accounted for, the spectral properties of coherent transition radiation can provide insights into the expansion of thin foil targets irradiated by intense laser pulse as well as the fast electron transport through it.