Klaus Petermann

A New Mixed Sesquioxide Yb:LuScO 3 : Spectroscopic Properties and Highly Efficient Thin-Disk Laser Operation

Spectroscopic properties and laser-operation of Yb:LuScO3are reported for the first time. Using the thin disk geometry 32.9W of output-power at 1039nm with a slope-efficiency of 81% was obtained from a 0.2mm-thick, 3.15at% Yb-doped disk.

Fabrication of a Stress-Induced Nd:YAG Channel Waveguide Laser Using fs-Laser Pulses

Using a fs-laser tracks were written in Nd:YAG. Due to stress induced birefringence waveguiding is possible in channels surrounding the tracks. Laser oscillation was achieved with an output-power of 132mW at 284mW of pump-power.

Yb-Doped Thin-Disk Laser Materials: A Comparison between Yb:LuAG and Yb:YAG

The impact of Yb-doping concentration on thermal conductivity is much lower in Yb:LuAG compared to Yb:YAG. As the materials have very similar spectroscopic properties, Yb:LuAG is supposed to outperform Yb:YAG in high power laser applications.

Mixed garnet laser crystals for water vapour DIAL transmitter

There are more or less well established technologies such as the optical-parametric-oscillator (OPO), the Raman-laser, and the Ti-Sapphire laser, which are able to emit laser light in the region of the water vapour absorption lines. For WALES the regions of about 935 nm, 942 nm, and 944 nm have been identified as the most suitable wavelength ranges. However, each of these laser designs is highly sophisticated. Current baseline for WALES is the Ti-Sapphire laser. A fourth possibility to achieve these wavelength ranges is to shift the groundstate laser lines (938 nm and 946 nm) of the Nd:YAG laser by replacing Aluminium and Yttrium by other rare earth elements. Changes of the host lattice characteristics lead to a shift of the upper and lower laser levels. These modified crystals are summarized under the name of Mixed Garnet crystals. Only the Mixed Garnet lasers can be pumped directly with diode laser and use a direct approach to generate the required laser pulses without frequency conversion. Therefore no additional non-linear crystals are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons. Such lasers have the great potential to fulfil the requirements and to become the preferred transmitter concept for WALES as well as for follow up missions. Within a ESA study several crystal compositions have been grown, spectrally characterised and analysed. Absorbed space radiation energy in the crystal lattice causes colour centres, which can reabsorb the pump and laser wavelength and consequently reduce the laser gain considerably. Co-dopants such as Chromium and Cerium are able to suppress the colour centres and are candidates for effective radiation hardening. The results of the crystal tuning, the co-doping with different radiation hardeners and the radiation tests will be presented. There applicability for a space based water vapour DIAL transmitter will be discussed.

Continuous-Wave Yb-Doped Sesquioxide Thin Disk Lasers with up to 300 W Output Power and 74% Efficiency

We obtained 301W of output power, 88% slope efficiency, and 74% optical-to-optical efficiency with VBG-diode-pumped Yb:Lu2O3 thin disk lasers. Yb:Sc2O3 and Yb:LuScO3 showed comparable performance, delivering 264W and 250W of output power, respectively.

Quenching processes in Yb lasers; Correlation to the valence stability of the Yb ion

We present an overview of quenching processes in Yb-doped lasers. Experiments made on Yb:YAG crystals and Yb-doped fiber lasers show that induced losses appear upon UV-irradiation through a charge-transfer process. The valence stability of the Yb ion is believed to be the key issue for the quenching processes in Yb-doped high power laser systems.

Passively Mode-Locked Yb:LuScO 3 Oscillator

Mode locking of the novel mixed sesquioxide crystal Yb:LuScO3 employing a SESAM is demonstrated. Pulse durations as short as 111 fs were obtained using a diode-laser pump source.

Efficient Mode-Locked Yb:Lu 2 O 3 Thin Disk Laser with an Average Power of 103 W

We demonstrate power scaling of an Yb:Lu2O3 thin-disk laser to an average power of 103 W setting a new record for mode-locked laser oscillators. The laser generates 885-fs pulses with an optical-to-optical efficiency of 42%.

Photoconductivity Measurements Indicating a Nonlinear Loss Mechanism in Highly Yb-Doped Oxides

Photoconductivity has been measured in highly Yb-doped oxides, revealing the occurrence of an up-conversion mechanism in these materials. A model for the observed phenomenon is suggested and the impact on thin-disk lasers is discussed.

Slow Nonradiative Decay for Rare Earths in KPb2Br5 and RbPb2Br5

We report on spectroscopic investigations of Nd3+- and Tb3+- doped low phonon energy, moisture-resistant host crystals, KPb2Br5 and RbPb2Br5, and their potential to serve as new solid state laser materials at new wavelengths.