Noncollinear gating of laser-plasma-driven attosecond pulses without spectral filtering

Abstract

Intense attosecond scale pulses of extreme-ultraviolet and soft X-ray light can be generated from plasma surfaces driven relativistically by intense laser pulses. The temporal profile consists of a train of pulses separated by the laser’s optical period and manifests in the spectral domain as harmonics of the laser frequency. Isolating individual attosecond pulses is a key challenge for applications of these sources to time-resolved experiments for attosecond science and plasma-based sources allow the use of ultra-high energies and intensities that can enable fully attosecond scale pump-probe measurements. Results are presented here for numerical Particle-In-Cell simulations of a scheme to angularly sweep the pulses so that one is temporally gated out from the others in the reflected direction. Using two identical laser pulses that are incident noncollinearly on the surface with a time delay causes the instantaneous wavefront to sweep between each of them with the attosecond pulses also being swept in their emission angle accordingly. This method naturally separates out the remaining reflected laser energy due to the angular gap between the incident pulses negating the need for spectral filtering after the interaction. We demonstrate clear gating of a single pulse along the reflected axis in both 2D and 3D simulations and discuss the effect of spectral isolation from the laser frequency. We extend the investigation to further examine techniques to improve the temporal gating by tailoring the laser and target properties.