Chirality plays a fundamental role in chemistry, biology, and materials science, influencing molecular recognition, drug activity, and optical functionality. Traditional chiral analysis methods, such as circular dichroism (CD) spectroscopy, have become indispensable, but they are limited by their reliance on a single absorption signal, low sensitivity to weakly chiral systems, and are unable to distinguish materials with complex spatial or multicentric chirality. Vortex beams, carrying orbital angular momentum (OAM) with a helical phase structure, introduce an additional spatial degree of freedom that enables helical dichroism (HD) spectroscopy. By tuning the topological charge (TC), HD can achieve multi-dimensional coupled detection of light intensity, phase, polarization and spatial topology, breaking through the one-dimensional limitation of CD. In this work, we review the physical foundation and experimental progress of HD from three perspectives: (1) the interaction mechanism between vortex beams and chiral matter; (2) transmission distortion analysis as a new detection dimension; and (3) AI-driven decoding for multidimensional signal extraction. Together, these advances demonstrate HD’s superior capability in resolving weak, complex, and dynamic chiral structures. Looking forward, integrating HD with metasurface control, intelligent signal processing, and on-chip detection is expected to establish a new generation of high-dimensional, adaptive chiral spectroscopy, paving the way for AI-assisted, chip-scale platforms capable of precise and real-time enantioselective analysis.
Ma et al. (Fri,) studied this question.