Unscrambling Structured Chirality with Structured Light at Nanoscale Using Photo-induced Force

TL;DR

This paper presents a microscopy method that uses structured light and photo-induced forces to detect and analyze the three-dimensional chirality of nanoscale samples, overcoming limitations of traditional circular polarization techniques.

Contribution

The authors introduce a novel structured light microscopy technique that can probe both transverse and longitudinal components of nanoscale sample chirality, enhancing detection capabilities.

Findings

Radially and azimuthally polarized beams effectively probe longitudinal chirality.

Circularly polarized waves only detect transverse polarizability components.

The technique has potential applications in stereochemistry, biomedicine, and material science.

Abstract

We introduce a microscopy technique that facilitates the prediction of spatial features of chirality of nanoscale samples by exploiting photo-induced optical force exerted on an achiral tip in the vicinity of the test specimen. The tip-sample interactive system is illuminated by structured light to probe both the transverse and longitudinal (with respect to the beam propagation direction) components of the sample magnetoelectric polarizability as the manifestation of its sense of handedness, i.e., chirality. We specifically prove that although circularly polarized waves are adequate to detect the transverse polarizability components of the sample, they are unable to probe the longitudinal component. To overcome this inadequacy, we propose a judiciously engineered combination of radially and azimuthally polarized beams, as optical vortices possessing pure longitudinal electric and magnetic field components along their vortex axis, respectively, hence probing longitudinal chirality. The proposed technique may benefit branches of science like stereochemistry, biomedicine, physical and material science, and pharmaceutics