Chirality-switchable spatially structured light via phase-segmentation modulation

This work presents a method for generating chirality-switchable spatially structured light (CSSSL) by regionally segmenting the wavefront into two zones, each loaded with distinct topological charges (<i>l</i>₁ ≠ <i>l</i>₂) by a spatial light modulator (SLM). The underlying mechanism is investigated using the Poynting vector and phase to gain insight into the behavior of the interference patterns. We reveal that the vortex beam phase exhibits a rotational tendency whose orientation reverses in front and back of the focal plane. The phase singularities arising from interference translate the rotational tendency from phase into intensity modulations, resulting in CSSSL. The interference structure of CSSSL varies with the ratio between the two regions. Furthermore, when|<i>l</i>₁ | < |<i>l</i>₂ |, the difference <i>Δ</i><i>l</i>=||<i>l</i>₁|-|<i>l</i>₂|| significantly influences the evolution of the optical energy flow pattern. This approach also enables the flexible generation of multiple CSSSL modes, including novel petal-like and double-ring patterns, depending on the relative magnitudes of |<i>l</i>₁ | and |<i>l</i>₂ |. Overall, CSSSL provides a simple yet powerful platform for extending helicity inversion from abstract phase to directly discernible intensity patterns, offering new opportunities for optical micromanipulation, chiral micro/nano-fabrication, information encoding, and precision optical detection.