Quantitative infrared photothermal microscopy

Infrared photothermal heterodyne imaging (IR-PHI) represents a convenient, table top approach for conducting super-resolution imaging and spectroscopy throughout the all-important mid infrared (MIR) spectral region. Although IR-PHI provides label-free, super-resolution MIR absorption information, it is not quantitative. In this study, we establish quantitative relationships between observed IR-PHI signals and relevant photothermal parameters of investigated specimens. Specifically, we conduct a size series analysis of different radii polystyrene (PS) beads to quantitatively link IR-PHI signal contrast to specimen heat capacity, thermo-optic coefficient, MIR peak absorption cross-section, and scattering cross-section at IR-PHI's probe wavelength.