Femtosecond laser inscribed 3D optical chirality

Chiral materials, owing to their unique capability to differentiate between spin states of light for their generation as well as detection and due to spin-orbit conversion of angular momentum, have garnered interest in photonic integrated circuits, optical sensing, and quantum optics. Yet, realizing large-scale, parameter-tunable, and cost-effective chiral nanostructures in inorganic crystals remains challenging. Metallic nanoparticles, widely used in various optical applications, offer a promising pathway. Their subwavelength field enhancement, arising from localized surface plasmon resonance, magnifies the absorption differences introduced by chiral configurations and enables rapid, large-area, precisely defined, and controllable in-situ system evolution under external electromagnetic excitation. Here, we present a novel strategy to generate optical chirality solely by manipulating encapsulated nanoparticles using femtosecond laser pulses and forming rotationally arranged nanoparticles within the yttrium aluminum garnet (YAG) lattice. Laser-induced symmetry breaking endows nanostructures inscribed in the 3D volume of the crystal with chiral optical responses that can be tailored from the visible to the near-infrared spectral range and are reproducible along two mutually orthogonal directions. The parameterizable and customizable chiral crystals enabled by this approach hold strong promise for diverse photonics fields including quantum photonics, paving the way for brand new applications of direct write laser nanolithography.