Two-photon excited fluorescence with shaped laser pulses for refractive beams

We report two-photon excited fluorescence of dyes for refracted laser beams by utilizing tailored laser pulses. A fluorescence contrast difference due to phase shaping could be achieved between different coumarin dyes. Particularly, an increased contrast difference is obtained for configurations close to the Brewster angle. Furthermore, by using a subsequent deformable phase plate for spatial shaping it was possible to precisely adjust the laser beam for controlled refraction at the liquid dye surface. A polarization-dependent refraction was observed when directing the shaped laser beam on the curved liquid adhesion meniscus close to the cuvette wall. This results in a refraction-dependent contrast difference. The presented method could be utilized for surface-sensitive biophotonic imaging applications.