Infrared photothermal heterodyne imaging: Contrast mechanism and detection limits

Infrared photothermal heterodyne imaging (IR-PHI) is an ultrasensitive technique for achieving super-resolution, infrared imaging throughout the mid-infrared “fingerprint” spectral region (2.5–10μm). An achieved spatial resolution of ∼300nm is up to 30-fold smaller than the infrared diffraction limit. In this study, we establish IR-PHI’s signal contrast mechanism and benchmark the technique’s capabilities using the characteristic infrared...