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

Photothermal microscopy enables high-sensitivity imaging of light-absorbing molecules; however, conventional implementations suffer from axial side-lobe artifacts that degrade accurate observation of three-dimensional structures. This study introduces a dual-probe photothermal microscopy approach that combines two probes at distinct axial positions with polarization-space-division balanced detection to suppress these artifacts without compromising probe power. Experiments using gold nanoparticles revealed that the side-lobe-to-main-lobe ratio decreased from 0.18 in conventional detection to 0.032 with the proposed method. Cross-sectional imaging of cedar pollen further demonstrated substantial suppression of spurious signals. This approach is compatible with dynamic specimens and extends the capability of photothermal microscopy for precise structural analysis.