Frequency conversion of ultrashort pulses via QPM

Lise Meitner Position M 583 Frequency conversion of ultrashort pulses via QPM Yiqiang QIN 08.05.2000 For many applications frequency conversion of laser radiation to other regimes than the laser medium provides is very desireable. Usually, nonlinear materials are used together with technologies like second harmonic generation (SHG) or optical parametric conversion (OPO or OPA). Phasematching is a very critical issue when pursuing this goal limiting the number of available materials drastically. Quasi-phasematching (QPM) of poled ferroelectrica or semiconductors is a rather new but successful technique with high versatility. It allows to cover wide wavelength regimes by careful engineering of samples which have to be poled in a certain sequence and prodedure in case of ferroelectrica or by multilayer semiconductor superlattices. Recently the development of (diode-pumped) solid-state lasers for the generation of ultrashort pulses (picosecond and femtosecond) has made a respectable progress. Cr3+ - doped LiSAF and related crystals being the most outstanding examples for transition metal doped broad-band laser media have reached the 10 fs regime at average output power levels of about 100 mW while certain rare earth-doped lasers like Yb:YAG have allowed to yield much more average power. Sub-picosecond pulses of an Yb:YAG thin disk laser have reached a level of about 15 W representing a tremendous potential for applications e.g. in materials processing. In the laboratory of the co-applicant at TU Vienna such lasers and others are under development. It is very desireable to convert those frequencies for various applications. Dr. Qin offers the appropriate skills and a very useful background for cooperation with his home university in Nanjing, China.