Single-sweep laser writing of 3D-waveguide devices.

We report on a method to create multiple waveguides simultaneously in 3D in fused silica. A combination of adaptive beam shaping with femtosecond laser writing is used to write two waveguides with changing separation and depth. The method is based on a programmable phase modulator and a dynamic variation of the phase-pattern during the writing process. The depth difference can be dynamically varied by changing a chirp parameter of the applied phase grating pattern. It can be employed in various photonic devices such as couplers, splitters and interferometers. Here we demonstrate splitters with both outputs ending in different depth.

12 MW peak power from a two-crystal Yb:KYW chirped-pulse oscillator with cavity-dumping.

We report on substantial pulse energy increase in Yb:KYW femtosecond laser oscillators by utilizing multiple laser crystals for an enhanced net-gain at higher pump power. The two-crystal oscillator generates pulse energies of 7 µJ at 1 MHz repetition rate which is, to our knowledge the highest energy ever reported from an Yb-doped tungstate fs-laser oscillator. The external pulse compression yields a pulse duration of 416 fs with a peak power of 12 MW being enough for stable white light generation in YAG.

Double waveguide couplers produced by simultaneous femtosecond writing.

We report on a novel method to create waveguide coupler devices in fused silica by combining the technique of beam shaping with femtosecond laser writing. The method is based on a programmable phase modulator and a dynamic variation of the phase-pattern during the writing process. The major advantage is the possibility to create complex devices in a single sweep by simultaneously writing two or more waveguides with changing separation. The guiding properties and the coupling behavior between the waveguides are investigated.

Theoretical and experimental limits of cavity-dumping in passively mode-locked thin-disk oscillators.

The dynamical properties of a mode-locked thin disk laser with cavity-dumping in the solitary regime are studied using numerical simulations along with experimental data. Limitations of this system as well as their origin are identified. The results of these investigations agree very well with recently published experimental results. Based on these findings design criteria for future systems are deducted and estimates of possible pulse energies are made.

Superresolved femtosecond laser nanosurgery of cells.

We report on femtosecond nanosurgery of fluorescently labeled structures in cells with a spatially superresolved laser beam. The focal spot width is reduced using phase filtering applied with a programmable phase modulator. A comprehensive statistical analysis of the resulting cuts demonstrates an achievable average resolution enhancement of 30 %.