Unambiguous definition of handedness for locally chiral light

Editors' Suggestion
Open Access

Unambiguous definition of handedness for locally chiral light

Ofer Neufeld and Oren Cohen

Phys. Rev. A 105, 023514 – Published 18 February 2022

Abstract

Synthetic chiral light fields were recently introduced as a novel source of chirality [Ayuso et al., Nat. Photonics 13, 866 (2019)]. This locally chiral light spans a three-dimensional polarization that plots a chiral trajectory in space-time, leading to huge nonlinear chiral signals upon interactions with chiral media. The degree of chirality of this new form of light was defined, characterized, and shown to be proportional to the chiral signal in high harmonic generation and photo-emission. However, the sign of the light's chirality—its “handedness”—has not yet been defined. Standard definitions of helicity are inapplicable for locally chiral light due to its complex three-dimensional structure. Here, we define an unambiguous handedness for locally chiral fields and employ it in practical calculations.

Received 15 November 2021
Accepted 31 January 2022

DOI:https://doi.org/10.1103/PhysRevA.105.023514

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Chirality Light-matter interaction Strong electromagnetic field effects

Laser spectroscopy

Spacetime symmetries

Atomic, Molecular & Optical

Authors & Affiliations

Ofer Neufeld ^1,2,* and Oren Cohen ²

¹Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Hamburg 22761 Germany
²Physics Department and Solid State Institute, Technion - Israel Institute of Technology, Haifa 32000, Israel

^*Corresponding author: oneufeld@schmidtsciencefellows.org

Article Text

Click to Expand

References

Click to Expand

Issue

Vol. 105, Iss. 2 — February 2022

Reuse & Permissions

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Illustration for handedness determination protocol in chiral molecules for the example of CBrClFH. The different substituents around the chiral center are numbered according to their weight, with the lightest group aligned pointing away from the viewer. An arrow is then drawn from the heaviest element towards the second heaviest element, which determines the handedness of the molecule, i.e., whether it is $R$ or $S$ (see text). (b) Illustration of main protocol for determination of the hDOC in locally chiral light. An exemplary Lissajous of a locally chiral field is plotted, which traces a chiral trajectory with its time-dependent polarization. Three unique vectors are chosen according to three unique moments in time, determined by the moment when the field's instantaneous intensity is maximized $(t_{1})$ . The normalized triple product of these vectors defines the handedness ( $h$ ) of the field.
Reuse & Permissions
Figure 2
Flow chart describing the complete protocol for determining locally chiral light's hDOC.
Reuse & Permissions
Figure 3
Numerical calculations of DOC and hDOC for exemplary cases of locally chiral light. In all subplots the hDOC of light is plotted across a one-dimensional interaction region where two collinear light beams overlap (and their relative phases oscillate). hDOC oscillates with the relative phases leading to various structures in the DOC that correspond to enhanced or weakened chiral responses. In all figures, blue refers to light with $R$ handedness, while red to light with $S$ handedness, and the $x$ axis is given in units of the wavelength, λ. (a) hDOC corresponding to case (A) described in the main text, where field parameters are taken from Fig. 5 in Ref. [21]. hDOC maintains a constant handedness across the interaction region. (b) hDOC corresponding to case (B) described in the main text, where field parameters are taken as in Fig. 2 in Ref. [27]. (c) hDOC corresponding to case (C) described in the main text, where field parameters are taken from Fig. 2 in Ref. [24]. (d) hDOC for a noncolinear field geometry similar to that in (C), but where the 2ω beam intensity in one of the arms is set to zero (the other beam parameters are taken randomly—the ellipticities are taken as 0.9:0.5:0.2 for the ω:ω:2ω beams respectively, the beam amplitudes ratios are 1:0.5:1 for the ω:ω:2ω beams respectively—but the result of chirality asymmetry along the $x$ axis is generally insensitive to these parameters).
Reuse & Permissions

Physical Review A

covering atomic, molecular, and optical physics and quantum information