M. R. Hofmann

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Photoacoustics (PA) is a new imaging modality based on the generation of ultrasound due to laser irradiation. Instead of commonly used Q-switched Nd:YAG lasers the application of pulsed laser diodes as light sources for photoacoustic imaging is proposed. The high pulse repetition frequency of laser diodes enables the usage of coded excitation schemes for(More)
Two-color semiconductor external cavity laser concepts for terahertz (THz) generation are discussed. By defining three critical characteristics, various two-color laser configurations are experimentally classified with respect to the application of THz generation. According to our experimental results, we suggest a new two-color laser configuration. It is(More)
Photoacoustics (PA) combines the high contrast of optical imaging modalities with the high resolution of clinical ultrasound. Photoacoustic contrast agents improve the maximum imaging depth of photoacoustic imaging and may render it possible to use this modality for molecular imaging. Organic dyes, like indocyanine green, or inorganic nanoparticles are used(More)
Spin-polarized lasers offer new encouraging possibilities for future devices. We compare time-resolved luminescence measurements with theoretical models for spin dynamics in spin-polarized lasers and demonstrate ultrafast polarization switching during one short single-mode laser pulse.
Nowadays silicon photonics gains more and more interest especially for the future architecture of Si based optoelectronic integrated circuits (OEI C). OEIC building blocks such a s modulators, detectors as well as light wave guides have been demonstrated in a down-scalable process technology. However, a commercial solution for the monolithic integration of(More)
Photoacoustic imaging is based on the generation of ultrasound using laser irradiation. Nd:YAG laser systems are commonly employed for this purpose, but cheap and handy pulsed laser diodes can be an attractive alternative. They emit significantly lower pulse energies, but fast averaging is feasible due to high repetition rates. Averaging is limited by the(More)
Optical selection rules for the interaction between light and matter lead to a direct connection between the spin of the carriers, e.g. in GaAs, and the polarization of the emitted or absorbed light. This enables spin-controlled photonic devices for the generation, transport and processing of spin information. For applications, room-temperature,(More)
THz time domain spectroscopy systems (TDS) have been finding their way into the market quite recently. Most of these systems use a laser source delivering ultra short laser pulses into a homodyne detection scheme based on photomixers. These sources are usually characterized by pulse lengths below 200fs, bandwidths of several THz and round trip frequencies /(More)
In the scope of this work we will present the influence of intracavity absorption in interplay with intracavity dispersion. The goal is to get a deeper insight into the physical effects of mode-locking of semiconductor laser diodes. This helps to verify theoretical models and possibly allows generating pulses shorter than 200 fs.