Widefield infrared photothermal imaging and spectroscopy

Infrared Photothermal Heterodyne Imaging (IR-PHI) is now a well-established, chemical and morphological characterization technique widely applicable to environmental and material science applications. Examples include studying micro- and nanoplastics in spectrally complex, chemical environments^[1] as well as monitoring cation migration in hybrid lead halide perovskites. IR-PHI has a spatial resolution of ~300 nm and works in a point-by-point scanning fashion. Time-expensive, single-point data acquisition limits image collection and subsequent material characterization. Here, we introduce a widefield modality to IR-PHI where photothermal IR images are acquired using a high-speed CMOS camera. The approach parallelizes data collection and makes possible hyperspectral imaging of specimens. Widefield image resolution and detection limits are established and compared with those of traditional IR-PHI.