Abstract
We have developed a thermal lens microscope which induces and detects photothermal effect at sub-single molecules level in/on liquids and condensed media. The thermal lens microscope can determine non-fluorescent molecules without receiving serious effect of light scattering in/on various condensed phase substances, and it can be applied to imaging of the distribution of non-fluorescent molecules by scanning on the sample. These characteristics of the thermal lens microscope are suitable for ultra sensitive analysis and imaging of biomedical substance in/on a single cell, separation media, and microfabricated chemical devises. We applied the thermal lens microscope to determine an ultratrace chemical species in various media.