Abstract
Vibrational spectroscopy can be applied to label-free microscopy of biological specimens to resolve the
disadvantages of fluorescence microscopy. Spontaneous Raman and coherent Raman scattering microscopy
have long been used for single-cell imaging, while infrared absorption microscopy has not due to
the low spatial resolution and large water absorption background. Recently, mid-infrared photothermal
microscopy has demonstrated single-cell infrared absorption imaging with a spatial resolution of the visible
light, which is a super-resolution in the context of mid-infrared microscopy. We have invented
wide-field mid-infrared photothermal quantitative phase microscopes with various phase imaging techniques.
