Ultra-short photon pulse generation in relativistic laser-plasmas

Optical pulse compression by the linear reflection of a laser pulse from a relativistically moving plasma is studied. Using Lorentz transformations, covariance of Maxwell's equations and the principle of phase invariance to transform between the rest frame and the moving frame, analytics can be exactly performed in the moving frame. Closed-form formulae for reflected waveforms as a function of incident angle show temporal compression and intensity amplification by a factor of 2γ and 4γ2, respectively, where γ is the Lorentz factor of the relativistic electron plasma. As an independent test, fully relativistic electromagnetic particle simulations agree well with analytical results, predicting pulse compression and large amplification to be of relevance to the generation of attosecond optical pulses. (paper)