Infrared nanospectroscopic imaging in the rotating frame
By: Samuel C. Johnson, Eric A. Muller, Omar Khatib, Elisa A. Bonnin, Alexander C. Gagnon, and Markus B. Raschke
Optica 6, 424-429 (2019)
Infrared (IR) vibrational scattering scanning near-field optical microscopy (𝑠-SNOM) has advanced to become a powerful nanoimaging and spectroscopy technique with applications ranging from biological to quantum materials. However, full spatiospectral 𝑠-SNOM continues to be challenged by long measurement times and drift during the acquisition of large associated datasets. Here, we demonstrate a novel approach of computational spatiospectral 𝑠-SNOM by transforming the basis from the stationary frame into the rotating frame of the IR carrier frequency. We demonstrate an acceleration of IR 𝑠-SNOM data collection by a factor of 10 or more in combination with prior knowledge of the electronic or vibrational resonances to be probed, the IR source excitation spectrum, and other general sample characteristics. As an example, we apply rotating-frame 𝑠-SNOM (R-sSNOM) to chemical nanoimaging of ultrathin protein sheets in a mollusk shell. R-sSNOM enables high-voxel-density imaging of sparsely distributed molecules in an extended matrix. It is generally applicable to many multiscale material systems with sparse features and can be extended to other spectroscopic nanoimaging modalities.