Double optical gating of high order harmonics from plasma surfaces

R E Smith,E White,B Dromey,P M Gilmore,M Yeung

doi:10.1088/1367-2630/ac2006

Abstract

Laser driven high harmonic generation from relativistically oscillating plasma surfaces is a promising route to isolated attosecond pulses with high peak brightness. Here we investigate a double optical gating scheme to restrict the emission to only a single, intense, attosecond pulse even with a multi-cycle driving laser. This scheme, which uses a second harmonic field, combined with a pair of counter-rotating circularly polarized laser pulses, leads to more efficient attosecond pulse generation with improved temporal isolation when compared to a single colour polarization gating scheme.

Highlights

An attosecond scale light source is the first step towards attosecond scale science
Laser driven high harmonic generation from relativistically oscillating plasma surfaces is a promising route to isolated attosecond pulses with high peak brightness
An investigation into isolating single attosecond pulses using a combination of two-colour high harmonic generation (HHG) from solid plasma surfaces and polarization gating at normal incidence was conducted using the 1D PIC code EPOCH

Summary

Introduction

An attosecond scale light source is the first step towards attosecond scale science. Isolated attosecond bursts lead the way to probing dynamics within physical systems, such as the movements of electrons in an atom [1], giving insight into the inner workings of physical processes which can occur on time scales of the order of a few thousandths of a femtosecond (1 as = 10−18 s) [2]. Since HHG from plasma surfaces can support higher intensity interactions, with comparable efficiencies to HHG from gas targets, attosecond pulses generated can have higher energies [4] These sources have the potential to provide both a sufficiently bright pump and probe [5], the high power laser systems required for these experiments are typically multicycle, a mechanism for generating intense, isolated attosecond pulses is required. As this drives the electron motion in the laser direction at twice the laser frequency, there are two emission events per laser cycle as opposed to one, as is the case for oblique incidence interactions This restricts the range of values that δtG must take to isolate a single pulse limiting the potential intensity that can be achieved with this gating technique when using a single colour driver. It will be possible to generate more intense, isolated attosecond bursts than compared to single colour schemes

Simulation set-up

Findings

Discussion of results

Conclusion