Ultrafast Photonics Group

An important part of the studies performed by members of the ultrafast photonics group is the development of ultrafast oscillators based on Ytterbium doped fibers and the realisation of novel pulse shapes allowing power scaling. Free-space components inside the laser set-up, e.g. optical isolators, wave-plates, beamsplitter etc. should be replaced by fiber-optical components in order to realize robust systems for industrial applications. Completely fiber-based set-ups have been already developed using a higher-order-mode (HOM) fiber for dispersion compensation. In addition, all normal dispersive Yb-fiber oscillators will be investigated with spectral filtering inside the laser cavity stabilizing the pulse forming process. By using a special fiber-based wavelength-division-multiplexer (WDM) another laser system without free-space section has been assembled.

Besides Ytterbium-based oscillators Thulium-doped ultrafast fiber lasers operating in the spectral range around 2 µm are topics of actual investigations. A corresponding system with intracavity dispersion compensation has been realized for the first time and different operation regimes could be demonstrated.

Additionally to these investigations, a research project for the investigation of compact, diode-pumped regenerative femtosecond amplifiers applying Yb-doped tungstate crystals is currently in progress. By combining spectral separated gain spectra or by using spatially chirped pulses inside the cavity a reduction of gain narrowing effects has been achieved. For that purpose several concepts based on two crystals with different orientations or single crystal arrangements with defined polarisation rotation inside the amplifier cavity have been realized.