Light at length scales far below the wavelength of light was the focus of today’s QAMSS lecture, delivered by Prof. Antonio Ambrosio of the Center for Nano Science and Technology at the Istituto Italiano di Tecnologia in Milan. His lecture, “Light at the Right Scale: Optical Probes for Low-Dimensional Materials”, explored how advanced optical and near-field techniques can reveal the behaviour of low-dimensional and van der Waals materials at the nanoscale.
Prof. Ambrosio discussed how these materials provide a powerful platform for controlling light, charge, vibrations, and mechanical response in regimes inaccessible to conventional optical microscopy. As optical excitations interact with nanoscale structures, they can propagate, localise, and be shaped by the intrinsic properties of the material.
The lecture introduced a range of optical probe techniques used to image and measure these effects, including scattering-type scanning near-field optical microscopy, hyperspectral imaging, and photoinduced-force detection. These approaches allow researchers to study light–matter interactions with spatial resolution far below the diffraction limit.
After outlining broader laboratory capabilities in dielectric metasurfaces and structured light, Prof. Ambrosio focused on van der Waals materials, where phonon and plasmon polaritons can be strongly confined. He showed how crystal anisotropy, hyperbolicity, and stacking geometry can be used to guide and manipulate optical excitations at the nanoscale.
The final part of the lecture highlighted recent work on strongly anisotropic layered systems, including α-MoO₃, hBN, twisted van der Waals structures, and MoOCl₂. These examples demonstrated how nanoscale optical probes can reveal canalised polariton propagation, visible and near-infrared hyperbolic response, and new routes for guiding light in natural crystals.
The lecture underlined the importance of optical probes as both diagnostic and discovery tools for next-generation quantum and advanced materials, opening new possibilities for nanophotonics, sensing, and light-based technologies.