Opportunities for chiral discrimination using high harmonic generation in tailored laser fields

TL;DR

This paper explores advanced techniques to enhance chiral discrimination using high harmonic generation with tailored laser fields, proposing new detection methods and theoretical insights for improved sensitivity and concentration-independent measurements.

Contribution

It introduces two-color counter-rotating elliptically polarized laser fields to significantly boost chiral dichroism and proposes a new approach for concentration-independent enantiomeric excess measurement.

Findings

Two-color counter-rotating fields increase chiral dichroism by an order of magnitude.

New detection schemes enable phase measurements of high harmonics.

Theoretical framework links observables to chiral response amplitude and phase.

Abstract

Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R. Cireasa et al ( Nat. Phys. 11, 654 - 658, 2015). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule C$_3$H$_6$O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independent measurement of the enatiomeric excess in a mixture of randomly oriented left-handed and right-handed molecules. Finally, for arbitrary configurations of laser fields, we connect the observables of the cHHG method to the amplitude and phase of chiral response, providing a basis for reconstructing wide range of chiral dynamics from cHHG measurements, with femtosecond to sub-femtosecond temporal resolution.