Tailoring the gradient and scattering forces for longitudinal sorting of generic-size chiral particles

Area of Science:

• Optics
• Photonics
• Nanotechnology

Background:

• Optical forces, including conservative (COF) and non-conservative (NCOF), are crucial for manipulating particles with light.
• Chirality sorting using optical forces is a key technique in fields like microfluidics and materials science.

Purpose of the Study:

• To investigate the physical mechanism behind longitudinal chirality sorting in optical fields.
• To analyze the roles of COF and NCOF in sorting particles of various sizes.
• To develop a method for effective chirality sorting of small particles.

Main Methods:

• Numerical and analytical modeling of optical forces acting on particles.
• Analysis of conservative and non-conservative optical forces (COF and NCOF).
• Investigation of particle size effects relative to the optical wavelength (λ).

Main Results:

• Longitudinal chirality sorting is solely dependent on NCOF, which reverses direction with particle chirality.
• For particles larger than λ/2, NCOF dominates, enabling sorting.
• For particles smaller than λ/2, COF dominates, hindering sorting.

Conclusions:

• A novel optical scenario is proposed to eliminate COF while preserving NCOF.
• This method extends the applicability of longitudinal chirality sorting to sub-wavelength particles.
• The findings offer new possibilities for chiral particle manipulation in micro-optics.