| 研究実績の概要 |
The properties of mirrors moving at relativistic velocities were first examined by Einstein in 1905. Relativistic mirrors (breaking plasma waves) generated by high intensity laser pulse propagating in a plasma have been shown both theoretically, numerically, and experimentally to be able to upshift laser light propagating in the direction opposite to the mirrors to higher frequencies. Only weakly relativistic laser pulses were considered so as not to strongly perturb the mirrors. We have shown by high resolution one dimensional simulations that even nearly relativistic intensity laser pulses can be reflected off the relativistic mirrors, upshifted and produce relativistically upshifted harmonics. Relativistically upshifted harmonics with wavelengths below 20 nm were generated from an originally 3 micron laser pulse approximately 160 times shorter than the original laser wavelength. When the intensity of the laser pulse is too strong, the reflected spectra do not have clear harmonic peaks. Two dimensional simulations have shown that strong laser pulses can be reflected and focused by the breaking plasma waves generated by another laser pulse. In addition via collaborations it has been shown that a high energy electron beam can generate GeV photons when scattered off multiple colliding laser pulses.
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