Inverse design of chiral structures for giant helical dichroism

Abstract

Investigating chiral light-matter interactions is essential for advancing applications in sensing, imaging, and pharmaceutical development. However, the chiroptical response in natural chiral molecules and subwavelength chiral structures is inherently weak, with the conventional characterization tools limited to optical methods that utilize circularly polarized light. To overcome this, optical vortex beams, characterized by helical wavefronts, have emerged as a compelling research focus. Helical dichroism (HD) represents the differential absorbance of vortex beams with opposite signs of topological charges. By using inverse design for topology optimization, we design the chiral structure for enhanced HD response under OAM beam incidence, demonstrating a giant HD response of ∼107% with topological charges |± 000000100 000001010 000010010 000010100 000011000 001110000 000100000 000100000 001100000 001101000 000110000 | = 3 at the wavelength of 800 nm. This study reveals distinct helicity-dependent interactions between the chiral structure and OAM beams, highlighting the potential for highly sensitive chiral devices.