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Strong-field control and enhancement of chiral response in bi-elliptical high-order harmonic generation: an analytical model
2018-05-30, Ayuso, David, Decleva, Piero, Patchkovskii, Serguei, Smirnova, Olga
The generation of high-order harmonics in a medium of chiral molecules driven by intense bi-elliptical laser fields can lead to strong chiroptical response in a broad range of harmonic numbers and ellipticities (Ayuso et al 2018 J. Phys. B: At. Mol. Opt. Phys. 51 06LT01). Here we present a comprehensive analytical model that can describe the most relevant features arising in the high-order harmonic spectra of chiral molecules driven by strong bi-elliptical fields. Our model recovers the physical picture underlying chiral high-order harmonic generation (HHG) based on ultrafast chiral hole motion and identifies the rotationally invariant molecular pseudoscalars responsible for chiral dynamics. Using the chiral molecule propylene oxide as an example, we show that one can control and enhance the chiral response in bi-elliptical HHG by tailoring the driving field, in particular by tuning its frequency, intensity and ellipticity, exploiting a suppression mechanism of achiral background based on the linear Stark effect.
Chiral dichroism in bi-elliptical high-order harmonic generation
2018-02-28, Ayuso, David, Decleva, Piero, Patchkovskii, Serguei, Smirnova, Olga
The application of strong bi-elliptically polarized laser fields to the generation of high-order harmonics in organic molecules offers exceptional opportunities for chiral recognition and chiral discrimination. These fields are made by combining an elliptically polarized fundamental, typically in the infrared range, with its counter-rotating second harmonic. Here we present a theoretical study of the harmonic emission from the chiral molecule propylene oxide in bi-elliptical fields. Our calculations include, for the first time in such a complex system, accurate photorecomination matrix elements, evaluated using the static-exchange density functional theory method. We show that bi-elliptical light can induce strong chiral dichroism in the harmonic spectra of chiral molecules in a broad range of harmonic numbers and ellipticities.
Highly efficient XUV generation via high-order frequency mixing
2020, Khokhlova, M.A., Strelkov, V.V.
The efficient generation of the coherent XUV light via frequency conversion of intense laser drivers is a problem of both fundamental and technological importance. Increasing the intensity of the generated high harmonics by raising the intensity of the driving field works only up to a point: at high intensities, rapid ionisation of the medium limits the conversion efficiency. Considering the combined effect of the phase-matching and of the blue shift of the driving field during its propagation in a rapidly ionising medium, we show that the latter can be the dominant limiting mechanism. We introduce a new spatial scale, the blue-shift length, which sets the upper bound for the quadratic intensity growth of the generated harmonics. Moreover, we show that this seemingly fundamental restriction can be overcome by using an additional generating weak mid-IR field. For specific combinations of frequencies of the generating fields, the corresponding high-order frequency-mixing process does not suffer from the blue shift of the drivers and phase mismatch, and thus its efficiency grows quadratically with propagation distance. Our results thus open a new route for highly efficient generation of coherent XUV light. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.