Synthesis of ultrashort laser pulses for high-order harmonic generation

E Neyra,G A Torchia,J A Pérez-Hernández,F Videla,L Roso,M F Ciappina

doi:10.1103/physreva.98.013403

Abstract

We present a technique for the synthesis of ultrashort laser pulses with approximately one cycle (FWHM) of temporal duration. These pulses are characterized by a certain degree of chirp. We show that these pulses produce both an enhancement of the high-order harmonic generation (HHG) cutoff and a noticeable increase of the yield, when interacting with an atomic system. Additionally, the asymmetric nature of the driven pulses plays an important role in the efficiency and cutoff extension of the high-order harmonics generated. Starting from the HHG spectra, we demonstrate it is possible to retrieve isolated attosecond pulses by spectral filtering. The analysis and interpretation of the different characteristics present in the HHG driven by this kind of pulse was carried out invoking classic arguments. Furthermore, a more complete description and validation of the HHG properties is performed by a quantum analysis, based on the integration of the time-dependent Schr\odinger equation in full dimensionality.

Highlights

In the last years, there has been a great advance in the generation of ultrashort laser pulses with stable carrier envelope phase (CEP)
As corollary we present the synthesis of attosecond pulses using the high-order harmonic generation (HHG) spectra that have larger cutoff and higher efficiency, i.e. the ones corresponding to pulses 1 and 3 [Figs. 3(a) and 3(c)]
We analyse four synthesized pulses with different characteristics and certain degree of chirp, all of them being obtained by varying the lengths L1 and L2 of a dispersive material, as well as the sign of its group velocity dispersion (GVD)

Summary

Introduction

There has been a great advance in the generation of ultrashort laser pulses with stable carrier envelope phase (CEP). These systems can deliver sub-two optical cycles, with energies in the sub-millijoule regime, in the spectral range of 0.8-2 μm [1,2,3]. HHG is one of the process that takes place when high intensity ultra-short laser pulses interact with atomic and molecular gaseous systems. This interaction generates a burst of high energy photons, typically in the XUV to soft-X-ray spectral range. These photons have odd frequencies of the original frequency, ω0, of the driving laser pulse [9,10,11]

Methods

Results

Conclusion