Highly versatile confocal microscopy system based on a tunable femtosecond Er:fiber source

Abstract

The performance of a confocal microscopy setup based on a single femtosecond fiber system is explored over a broad range of pump wavelengths for both linear and nonlinear imaging techniques. First, the-benefits of a laser source in linear fluorescence excitation that is continuously tunable over most of the visible, spectrum are demonstrated. The influences of subpicosecond pulse durations on the bleaching behavior of typical fluorophores are discussed. We then utilize the tunable near-infrared output of the femto-second system in connection with a specially designed prism compressor for dispersion control. Pulses as short as 33 fs are measured in the confocal region. As a consequence, 2 mW of average power are sufficient for two-photon microscopy in an organotypic sample from the, mouse brain. This result shows great prospect for deep-tissue imaging in the optimum transparency window around 1100 nm. In a third experiment, we prove that out, compact setup is powerful enough to exploit even higher-order non-linearities such as three-photon absorption that we use to induce spatially localized photodamage in DNA.