We present a femtosecond laser system at 920 nm delivering ultrashort pulses via a hollow-core photonic bandgap fiber (HC-PBGF). The laser system is designed to simplify two-photon microscopy applications and can be used for miniaturized two-photon microscopes. While previously presented solutions have been tailored to a specific length and dispersion coefficient of the HC-PBGF, we now show a compact and flexible scheme for dispersion compensation which is compatible with a wide range of fiber types and lengths.
In addition, this new approach fully maintains the capability of software-controlled dispersion compensation in the range from 0 to -40,000 fs2 after the pulse delivery fiber. Hence, the dispersion of common two-photon microscopes can be pre-compensated in order to obtain compressed pulses at the sample plane. Our newly developed system displays excellent long-term fiber coupling stability under varying environmental conditions. It is capable of polarization-preserving femtosecond pulse delivery at 920 nm and reaches Watt-level power after the delivery fiber, making it suitable for in-vivo brain imaging of GCaMP in mouse models.
We present time resolved measurements on low dimensional nanomaterials like individual (6,4) single-walled carbon nanotubes and monolayers of MoSe2 via transient interferometric scattering (TiSCAT) microscopy. For this a novel fiber laser system was developed comprising a tunable probe arm and low noise performance. The sensitivity of the measurement is demonstrated for very low excitation powers to prevent photodamage of the sample. Signal variations close to the shot-noise limit can be resolved even with low excitation powers in the order of 1 μW. In combination with the tunability of the laser system the absorption spectrum of a single SWCNT was determined.
We present a femtosecond laser written, apodized chirped fiber Bragg grating (acFBG) used for dispersion control inside picosecond all-fiber lasers. A fiber fixation setup enables a plane-by-plane (pbp) written acFBG in a standard, polarization-maintaining fiber by applying a beam-slit configuration. The spectral specifications of the acFBG are examined in detail, and the grating is validated inside a mode-locked fiber laser oscillator. This letter provides a route to the fast prototyping of acFBGs with customized parameters for use as dispersion compensating elements inside ultrafast all-fiber lasers.
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