Generation of synchronized high-intensity x-rays and mid-infrared pulses by Doppler-shifting of relativistically intense radiation from near-critical-density plasmas

TL;DR

This paper demonstrates that reflecting relativistically intense ultrashort laser pulses from near-critical-density plasmas can generate synchronized high-intensity X-ray and mid-infrared pulses through Doppler frequency shifting, enabling advanced spectroscopy techniques.

Contribution

It introduces a novel method for producing synchronized high-intensity X-ray and mid-infrared pulses via Doppler-shifted reflection from near-critical-density plasmas.

Findings

Energy conversion efficiency into >3 μm wavelength range can reach several percent.

Generated mid-infrared pulses are relativistically intense and synchronized with high harmonics.

Method enables high-precision pump-probe measurements such as electron diffraction.

Abstract

It is shown that when relativistically intense ultrashort laser pulses are reflected from the boundary of a plasma with a near-critical density, Doppler frequency shift leads to generation of intense radiation both in the high-frequency, up to the X-ray, range, and in the low-frequency, mid-infrared, range. The efficiency of energy conversion into the wavelength range of greater than 3 $\mu$m can reach several percent, which makes it possible to obtain relativistically intense pulses in the mid-infrared range. These pulses are synchronized with high harmonics in the ultraviolet and X-ray ranges, which opens up opportunities for high-precision pump-probe measurements, in particular, laser-induced electron diffraction and transient absorption spectroscopy.