Bi-modal photothermal/optical microscopy for complementary bio-imaging with high resolution and contrast.

In the paper, combined bimodal microscopic visualization of biological objects based on reflection-mode optical and photoacoustic measurements was presented. Gasmicrophone configuration was chosen for the registration of photothermal response. Precise positioning of the scanning laser beam with modulated intensity was performed employing acousto-optic deflectors. Photoacoustic images are shown to give complementary details to the optical images obtained in the reflected light. Specifically, the photoacoustic imaging mode allows much better visualization of the features with enhanced heat localization due to the reduced heat outflow. For example, the application of the photoacoustic imaging mode was especially successful to visualize Drosophila fly's micro-hairs. Furthermore, the photoacoustic image quality was shown to be adjusted through modulation frequency.