We report optical absorption and photocurrent measurements on a GaN/AlN-based superlattice. The optical absorption has a full width at half maximum of 120 meV and takes place at an energy of 660 meV (5270 cm−1); this corresponds to a wavelength of 1.9 μm. While the optical absorption remained unchanged up to room temperature, the photocurrent signal could be observed up to 170 K. With respect to the optical absorption, the photocurrent peak was slightly blueshifted (710 meV/5670 cm−1) and had a narrower width of 115 meV. Using this quantum-well infrared photodetector, we were able to measure the spectrum of a 1.55 μm superluminescent light-emitting diode.

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Under pulsed operation, time dependent spectral and electro-optical measurements on GaN-based laser diodes show a considerable red shift in the emission wavelength and a decreasing voltage drop across the device. These changes appear on a rather short time scale in the microsecond range. During a 3.7 microsecond long pulse, a temperature increase of approximately 50 K is obtained using different experimental methods. This value agrees well with numerical simulations based on the thermal properties of the material.

We report on a thin-disk laser system with more than 10 kW of output power and a beam quality of M 2 = 1.76 at an overall optical-to-optical efficiency of 51%. The system consists of two thin-disk laser oscillators and a thin-disk multi-pass amplifier system. To reach high output powers while maintaining good beam quality, the output beams of two identical laser oscillators are polarization-combined. Subsequently, the beam is amplified in a multi-pass system. To the best of our knowledge, this is the highest output power achieved for a thin-disk laser system with a beam quality close to fundamental mode.