Diffraction limits the resolution of standard optical microscopes. Breaking the diffraction limit is the motivation behind Scanning Probe Microscopy (SPM) that includes Atomic Force Microscopy (AFM) and Near-field Scanning Optical Microscopy (SNOM). SPMs create high-resolution maps of the sample’s surface by scanning the sample with nanometric probes. SNOM in particular, can simultaneously provide information on the morphology and on the optical properties of materials by illuminating the sample with a localized field provided by the microscope probe. In SNOM microscopy, the amount of light to be detected is low, a million times weaker than the illuminating light. This forces to implement complex background suppression schemes based on interferometers and would be unrealistic to be adapted to Space Science.
Recently, we contributed developing a new optical scanning probe technique that provides nanometric resolution optical images without detecting any light. Such "Dark" microscopy is counterintuitive but possible. The technique is based on the detection of the weak optical forces established between the sample surface and the microscope probe when both are illuminated. Such scheme (photo-induced force microscopy (PiFM) ) has intrinsic background suppression, avoiding complex interferometric schemes.
Scope of this Early Technology project is to develop broadband PiFM-based nano-spectroscopy in the visible and near-IR spectral range. In order to achieve such goal, a new light modulation scheme will be implemented based on specifically designed optical metasurfaces.
Several applications can be immediately enabled by the spatial and spectral resolution of the proposed technology, one above all, the recognition of molecular species in organic and inorganic specimens, from minerals to bacteria and viruses.
