Measurement of two-photon-absorption spectra through nonlinear fluorescence produced by a line-shaped excitation beam

Line-Shaped Illumination: A Promising Configuration for a Flexible Two-Photon Microscopy Setup

An innovative two-photon microscope exploiting a line-shaped illumination has been recently devised and then implemented. Such configuration allows to carry out a real-time detection by means of standard CCD cameras and is able to maintain the same resolution as commonly used point-scanning devices, thus overcoming what is usually regarded as the main limitation of line-scanning microscopes. Here, we provide an overview of the applications in which this device has been tested and has proved to be a flexible and efficient tool, namely imaging of biological samples, in-depth sample reconstruction, two-photon spectra detection, and dye cross-section measurements. These results demonstrate that the considered setup is promising for future developments in many areas of research and applications.

Practical two-photon-absorption cross sections and spectra of eosin and hematoxylin

We experimentally investigate the two-photon absorption cross sections and spectra of eosin and hematoxylin for applications in nonlinear microscopy. The experiments are carried out on pure samples of the two dyes in DI-water solvent with different concentrations, in the typical range employed in standard staining procedures. Nonlinear fluorescence is excited by a line-shaped beam emitted by a Ti:Sapphire mode-locked laser in the wavelength range from 740 to 880 nm and is detected through a microscope setup. The two-photon absorption spectral response is systematically analyzed and discussed. Finally, the staining is applied on biological tissue samples, which are imaged by two-photon microscopy. Our results show that the employed dyes are fully suitable for applications in nonlinear imaging.