The interaction between light and materials is fundamental to many cutting-edge technologies, from high-speed communications to ultra-sensitive sensors. When light couples to collective lattice vibrations at a crystal surface, it creates unique quasi-particles called surface phonon polaritons. These hybrid light-matter excitations enable precise control over light at the nanoscale, paving the way for next-generation photonic devices. Until now, studying these evanescent modes has relied on tip-based scanning techniques, which, while powerful, are often time-consuming and limited in their ability to capture the full vector field of polariton modes.
In their latest work published in Optical Materials Express, the Lattice Dynamics group and their collaborators employ wide-field sum-frequency generation spectro-microscopy. In this approach a visible laser is overlapped with the in-house infrared free electron laser (FHI-FEL) to image the polaritons excited in the infrared with visible resolution. This method allows for selective probing of in-plane polariton field components, offering a faster and more comprehensive way to study complex nanophotonic structures. By combining high spatial resolution with polarization-sensitive imaging, the team demonstrates a powerful tool for uncovering the intricate dynamics of polaritons, opening new avenues for high-throughput nanophotonic research.