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We present the tuning of the dispersion properties of a femtosecond (fs) laser inscribed chirped fiber Bragg grating (CFBG), realized by selectively modifying the refractive index of the already inscribed CFBG by fs laser post-processing. This Letter demonstrates for the first time, to the best of our knowledge, a flexible approach for tailoring higher-order dispersion terms of a fs inscribed CFBG via fs post-processing of selected grating regions, thus paving the way, e.g., for applications in dispersion management of ultrashort pulse fiber lasers.

We present highly robust fiber Bragg gratings (FBGs) in passive large-mode-area fibers for kilowatt fiber laser systems. The gratings were inscribed directly through the fiber coating using near-infrared femtosecond laser pulses and then implemented in an all-fiber ytterbium-doped single-mode oscillator setup reaching up to 5 kW signal output power. The untreated cooled FBGs showed thermal coefficients as low as ${1}\;{\rm K}\;{{\rm kW}^{ - 1}}$1KkW -1 , proving excellent qualification for the implementation into robust high-power fiber laser setups.

We investigate the high-power durability of fiber Bragg gratings written directly into an ytterbium-doped large mode area fiber using ultrashort laser pulses. The gratings were successfully integrated as a high reflector into an oscillator setup reaching up to 1.9 kW signal output power with an efficiency of 87%. Defect states induced during the inscription process could be drastically reduced by a self-annealing process resulting in a stable laser performance.

We demonstrate the fabrication of aperiodic fiber Bragg gratings (AFBGs) for their application as filter elements. Direct inscription was performed by focusing ultrashort laser pulses with an oil-immersion objective into the fiber core and utilizing the line-by-line technique for flexible period adaptation. The AFBGs inscribed allow for the suppression of 10 lines in a single grating and are in excellent agreement with simulations based on the specific design. Applications in astronomy for the suppression of hydroxyl emission lines are discussed.

The period of fiber Bragg gratings is adapted by shaping the wavefronts of ultrashort laser pulses applied in a phase mask inscription technique. A specially designed deformable mirror, based on a dielectric substrate to withstand high peak powers, is utilized to deform the wavefront. A shift of about 11 nm is demonstrated for a Bragg wavelength around 1550 nm.

Ultrashort laser pulses are used to inscribe volume Bragg gratings (VBGs) into fused silica. These VBGs demonstrate excellent performance for the external stabilization of laser diode bars. The stabilized system emits at a wavelength of 969 nm with a signal width (FWHM) of 100 pm and shows a spectral drift as low as 24 pm for a change in output power of 45 W for a grating surface area of 10  mm 2 .