Anomalous Relativistic Emission from Self-Modulated Plasma Mirrors

The interaction of relativistically intense laser pulse with a plasma mirror produces harmonics of the incident frequency co-propagating in the direction of specular reflection due to the plasma mirror surface oscillating with velocity close to the speed of light. This mechanism has shown its potential for realization of a bright source of extreme ultraviolet radiation and attosecond pulses. Here, we reveal an unexpected transition of this well-known process into a new regime of efficient extreme ultraviolet radiation generation. A novel mechanism of relativistic emission of radiation from plasma mirrors is identified with an extraordinary property that instead of following specular reflection, the radiation is emitted in the direction along the plasma mirror surface. With analytical calculations and numerical particle-in-cell simulations, we show that this radiation originates from laser-driven non-linear oscillations of relativistic electron nanobunches that are generated by a plasma surface instability and propagate along the plasma mirror surface.Comment: 6 pages, 3 figure

The Effect of Ultrastrong Magnetic Fields on Laser-Produced Gamma-Ray Flashes

Laser produced $gamma$-photons can make an important impact on applied and fundamental physics that require high $gamma$-photon yield and strong collimation. We propose addition of a constant magnetic field to the laser-solid interaction to obtain the aforementioned desired $gamma$-photon properties. The $gamma$-ray flash spatial and spectral characteristics are obtained via quantum electrodynamics particle-in-cell simulations. When the constant magnetic field aligns with the laser magnetic field then the $gamma$-ray emission is significantly enhanced. Moreover, the $gamma$a-photon spatial distribution becomes collimated, approximately in the form of a disk.Comment: 5 pages, 5 figure