Superresolution vibrational imaging by simultaneous detection of Raman and hyper-Raman scattering

High spatial resolution of topographic imaging and Raman mapping by differential correlation-confocal Raman microscopy

Confocal Raman microscopy (CRM) has found applications in many fields as a consequence of being able to measure molecular fingerprints and characterize samples without the need to employ labelling methods. However, limited spatial resolution has limited its application when identification of sub-micron features in materials is important. Here, we propose a differential correlation-confocal Raman microscopy (DCCRM) method to address this. This new method is based on the correlation product method of Raman scattering intensities acquired when the confocal Raman pinhole is placed at different (defocused) positions either side of the focal plane of the Raman collection lens. By using this correlation product, a significant enhancement in the spatial resolution of Raman mapping can be obtained. Compared with conventional CRM, these are 23.1% and 33.1% in the lateral and axial directions, respectively. We illustrate these improvements using in situ topographic imaging and Raman mapping of graphene, carbon nanotube, and silicon carbide samples. This work can potentially contribute to a better understanding of complex nanostructures in non-real time spectroscopic imaging fields.

Superresolution concentration measurement realized by sub-shot-noise absorption spectroscopy

Absorption spectroscopy is one of the most widely used spectroscopic methods. The signal-to-noise ratio in conventional absorption spectroscopy is ultimately limited by the shot noise, which arises from the statistical property of the light used for the measurement. Here we show that the noise in absorption spectra can be suppressed below the shot-noise limit when entangled photon pairs are used for the light source. By combining broadband entangled photon pairs and multichannel detection, we realize the acquisition of sub-shot-noise absorption spectra in the entire visible wavelength. Furthermore, we demonstrate the strength of sub-shot-noise absorption spectroscopy for the identification and quantification of chemical species, which are two primary aims of absorption spectroscopy. For highly diluted binary mixture solutions, sub-shot-noise absorption spectroscopy enables us to determine the concentration of each chemical species with precision beyond the limit of conventional absorption spectroscopy. That is, sub-shot-noise absorption spectroscopy achieves superresolution in concentration measurements.

Detection of solvent/buried TiO2 surface interactions by intermolecular Fano resonance in resonance hyper-Raman scattering

We report a new phenomenon that may possibly enable the selective detection of solvent/surface interactions on a buried TiO(2) surface. A mechanism based on intermolecular Fano resonance involving a solvent vibrational mode and a TiO(2) phonon mode is proposed, which suggests that the strong electronic character of the TiO(2) phonon mode plays an important role. The solvent vibrational mode that takes part in Fano resonance can be significantly enhanced with the help of the intense resonance hyper-Raman band of a TiO(2) phonon mode, and this allows us to selectively detect the solvent/surface interactions even from a buried surface.