Spectrally and Repetition Rate Tunable Femtosecond Fiber Laser for Two-Photon Biomedical Imaging Applications

The current extremely rapid development of biomedical imaging techniques, such as OCT and multiphoton microscopy, requires the development of light sources with very sophisticated parameters. We present a femtosecond laser emitting at the borderline of visible and near-infrared range (760–800 nm). The intended application is in two-photon excited fluorescence microscopy, in which a fluorophore simultaneously absorbs two photons from the excitation beam. Compared to traditional (single-photon) fluorescence microscopy, the two-photon variant allows deeper penetration into imaged tissue, lower phototoxicity, and guarantees confocality (without the need for an aperture) [1]. This technique makes it possible to image, for example, the retina of the eye [2]. The laser we propose is an all-fiber-based solution that is an alternative to the titanium-sapphire lasers currently in use, offering compactness so that it can be easily integrated into existing devices (such as microscopes or ophthalmoscopes).