Exploiting light with a twist: Light possesses several degrees of freedom that can be exploited to encode information. In addition to wavelength, amplitude, phase, polarization, and pulse length, light can also be structured into vortices. These vortices carry optical angular momentum, effectively opening up many other modes as communication channels. Ni et al . review advances made in the nanophotonic platform where optical vortices can be generated and detected on-chip. These developments are expected to find application in classical and quantum information processing. —ISO

Significance: Optical chirality by light–matter interaction is a powerful strategy for discriminating the chirality of materials in modern physics. Here we present a vortex-dependent approach to yield a direct chiroptical response with monochromatic light. The chiroptical signal of ∼120% is obtained on intrinsically chiral microstructures by optical vortices in the visible range. The chiroptical properties of microstructures can be flexibly controlled by tuning their geometric features. We further demonstrate the strong chiral light–matter interaction by optical vortices for sensitively detecting optical chirality of molecules.

Advanced control over the excitation of ultraconfined polaritons—hybrid light and matter waves—empowers unique opportunities for many nanophotonic functionalities, e.g., on-chip circuits, quantum information processing, and controlling thermal radiation. Recent work has shown that highly asymmetric polaritons are directly governed by asymmetries in crystal structures. Here, we experimentally demonstrate extremely asymmetric and unidirectional phonon polariton (PhP) excitation via directly patterning high-symmetry orthorhombic van der Waals (vdW) crystal α-MoO ₃ . This phenomenon results from symmetry breaking of momentum matching in polaritonic diffraction in vdW materials. We show that the propagation of PhPs can be versatile and robustly tailored via structural engineering, while PhPs in low-symmetry (e.g., monoclinic and triclinic) crystals are largely restricted by their naturally occurring permittivities. Our work synergizes grating diffraction phenomena with the extreme anisotropy of high-symmetry vdW materials, enabling unexpected control of infrared polaritons along different pathways and opening opportunities for applications ranging from on-chip photonics to directional heat dissipation.