Enhancing high-order harmonic generation by sculpting waveforms with chirp

Abstract

We present a theoretical analysis showing how chirp can be used to sculpt two-color driving laser field waveforms in order to enhance high-order harmonic generation (HHG) and/or extend HHG cutoff energies. Specifically, we consider driving laser field waveforms composed of two ultrashort pulses having different carrier frequencies in each of which a linear chirp is introduced. Two pairs of carrier frequencies of the component pulses are considered: (ω, 2ω) and (ω, 3ω). Our results show how changing the signs of the chirps in each of the two component pulses leads to drastic changes in the HHG spectra. Our theoretical analysis is based on numerical solutions of the time-dependent Schrödinger equation and on a semiclassical analytical approach that affords a clear physical interpretation of how our optimized waveforms lead to enhanced HHG spectra.

Femtosecond Single Cycle Pulses Enhanced the Efficiency of High Order Harmonic Generation

“…Here, extensive theoretical works evoking different schemes have been devoted to achieve this goal. For instance, the use of chirped laser pulses [11][12][13], and the spatial inhomogeneity of the laser field [14,15] have been shown to lead to an extension of the cutoff region and or enhancing the intensity of HHG. Other schemes involving static electric fields have also been used to control HHG [16][17][18][19], although are not appropriate for time-resolved applications nor for attosecond metrology.…”

Controlling resonant enhancement in higher-order harmonic generation

“…After the conceptualization of the HHG, the research in this field is aimed toward enhancing the harmonic cutoff of the HHG and increasing the corresponding intensity of the emitted harmonics. Different pulse shaping techniques are introduced in the past to achieve these objectives [11][12][13][14][15]. However, the resonant enhancement of harmonic emission is now seen to be a very promising aspect of HHG [16,17].…”

Detailed study of quantum path interferences in high harmonic generation driven by chirped laser pulses

“…These properties can be accessed through the investigation and shaping of the XUV spectral (or equivalently temporal) phase behaviour by the simultaneous tuning of specific parameters of the intense ultrashort laser pulse that drives the high harmonic generation process [16]. In particular, the effect of the fundamental pulse's chirp on GHHG process has been the subject of studies for several years [17,18], and is still actively pursued [19,20]. The harmonic spectral phase is inherently determined by the microscopic generation process theoretically described by the response of an individual atomic dipole to the strong alternating electric field.…”