Dual-probe photothermal microscopy for suppression of side-lobe artifacts

Photothermal microscopy enables high-sensitivity imaging of light-absorbing molecules, but conventional implementations suffer from axial side-lobe artifacts that hinder accurate observation of three-dimensional structures. This study introduces dual-probe photothermal microscopy that employs probes at distinct focal planes, combined with polarization–space-division balanced detection, to suppress such artifacts. Experiments with gold nanoparticles revealed a reduction in the main-lobe-to-side-lobe ratio from 0.18 to 0.032 when compared with conventional methods. Moreover, the application of the method to cedar pollen demonstrated substantial improvement in three-dimensional structural imaging with reduced artifacts. This approach is compatible with dynamic specimens and extends the capability of photothermal microscopy for precise structural analysis.