High resolution IR spectroscopy and imaging based on graphene micro emitters

Abstract: IR spectroscopy such as Fourier transform infrared spectroscopy (FTIR) are widely used for the investigation of structure and the quantitative determination of substances in the fields of chemistry, physics, biology, medicine, and astronomy, because the energy of IR absorption corresponds to the energy for each vibrational transition in functional groups within molecules. Microscopic imaging of FTIR is used for various practical applications, as it enables visualization of the composition distribution and changes in molecular structure without fluorescent labels. However, FTIR microscopy with an objective lens has a diffraction limit causing the low spatial resolution with the order of 10 $\mu$m. Here, we present high-spatial-resolution IR spectroscopy and imaging based on graphene micro-emitters, which have distinct features over conventional IR sources: a planar structure, bright intensity, a small footprint (sub $\mu$m$^2$), and high modulation speed of ~100 kHz. We performed IR absorption spectroscopy on a polymer thin film using graphene micro-emitters, realizing high-resolution IR imaging with a spatial resolution of ~2 $\mu$m, far higher than that of the conventional FTIR. We show the two-dimensional IR chemical imaging that visualizes the distribution of the chemical information, such as molecular species and functional groups. This technique can open new routes for novel IR imaging and microanalysis in material science, physics, chemistry, biology, and medicine.