Reflection of electromagnetic waves from an ionization front

Frequency up-conversion and trapping of ultrashort laser pulses in semiconductor plasmas

“…Phenomena arising in the course of the interaction of electromagnetic waves with a moving ionization or recombination fron t (separating the neutral gas from the plasma) have attracted considerable attention in the past [14]. Due to recent technological advances in producing short ultrastrong laser pulses, there is a resurgence of interest in this old problem [15].…”

Relativistic Doppler frequency upconversion of terahertz pulses reflecting from a photoinduced plasma front in silicon

“…To achieve a significant upshift factor, the boundary must possess a velocity comparable with that of the incident light, as can be realized, e.g., via an accelerated electron beam [2] or from rapid motion of charges in a nonuniform plasma [3][4][5][6][7]. It was also realized [8,9] that the moving boundary does not have to involve longitudinal motion of the constituent material particles, i.e., one may also employ an ionization front, where the motion of the plasma discontinuity is due to a counterpropagating optical excitation pulse. The frequency upshift factor = ω r /ω i between the incident (ω i ) and reflected (ω r ) waves is ideally given by = (1 + β)/(1 − β), where β = U/c in terms of the propagation speeds of the plasma front (U ) and incident radiation c (in the medium [10]).…”

The flying mirror: future brightest x-ray and γ-ray source

“…The reflection at the moving ionization fronts was studied in Refs. [20][21][22]. Further examples of the manifestation of the Doppler effect in plasma whose dynamics is governed by the strong collective fields are seen in the concepts of the flying mirror, 6 sliding mirror [23][24][25] (which can be interpreted in terms of the transverse Doppler effect), oscillating mirror [26][27][28][29][30][31][32][33] and other schemes [34][35][36][37][38] .…”