Millimeter-Scale Wide-Field Mid-Infrared Photothermal Imaging Enabled by a Broadly Tunable Picosecond Optical Parametric Oscillator

Abstract Wide-field mid-infrared photothermal (MIP) imaging enables chemically specific microscopy with submicron spatial resolution but remains fundamentally limited by the trade-off between field of view, mid-infrared pulse energy, and spectral tunability. As a result, current wide-field implementations are typically restricted to fields of view (FOVs) below 200 μm and to either the fingerprint or high-wavenumber spectral regions. Here, we present a wide-field fluorescence-detected MIP (F-MIP) platform driven by a commercial picosecond optical parametric oscillator (OPO) delivering up to 360 μJ across 625–4347 cm–1, enabling millimeter-scale imaging in the high-wavenumber region (∼1 mm FOV, 0.5–5 μm polystyrene beads) and, to our knowledge, the first wide-field MIP imaging below 900 cm–1. Large-area mosaic imaging of tuberculosis-infected tissue sections demonstrates chemically resolved mapping over millimeter-scale biomedical specimens, establishing OPO-driven F-MIP as a scalable platform for high-throughput vibrational imaging.