Isolated sub-100-as pulse generation by optimizing two-color laser fields using simulated annealing algorithm

Li Zheng,Songsong Tang,Xianfeng Chen

doi:10.1364/oe.17.000538

Abstract

We propose a method to broaden the cut-off region of high harmonic generation by optimizing the parameters of two-color laser fields synthesized by an intense 5 fs pulse at 800 nm and a relatively weak, subharmonic pulse at 2400 nm. Simulated Annealing (SA) algorithm is employed to optimize the electric field amplitude, pulse duration of the control pulse, and the time delay between two pulses. Our simulation shows that a broadened XUV supercontinuum with a 115 eV spectral width can be generated, which is two times broader compared with no optimization, and directly creates an isolated 76as pulse even without any phase compensation.

Highlights

The advent of attosecond extreme ultraviolet pulses opens up a new regime of tracking ultrafast electron processes in atoms and molecules with unprecedented time resolution [1, 2]
It has been theoretically demonstrated that the attosecond pulse bandwidth can be significantly broadened in a two-color laser field [7,8], because the effect of two-color field is essentially equivalent to shortening the few-cycle pulse duration and maximally utilized the driving laser energy
Simultaneously in the available scope of laser conditions, and got a dramatically increased XUV supercontinuum with spectral width of 115eV, which is nearly two times broader compared with no optimization

Summary

Introduction

The advent of attosecond extreme ultraviolet pulses opens up a new regime of tracking ultrafast electron processes in atoms and molecules with unprecedented time resolution [1, 2]. It has been theoretically demonstrated that the attosecond pulse bandwidth can be significantly broadened in a two-color laser field [7,8], because the effect of two-color field is essentially equivalent to shortening the few-cycle pulse duration and maximally utilized the driving laser energy. Zeng et al simulated the HHG using a weak second harmonic control pulse adding upon an intense few-cycle fundamental pulse and generated a supercontinuum with spectral width of 148eV[9]. We optimized the electric field amplitude and pulse duration of control pulse, and the initial time delay between the two pulses simultaneously for the first time to generate an isolated sub-100-as pulse

Theoretical details and simulation results

Conclusion