Femtosecond laser system with tunable OPA

The femtosecond laser system will be used to generate and detect broadband terahertz radiation through optical rectification - laser-induced plasma generation or photoconductive antennas. These methods need femtosecond pulses - and the pulse duration directly sets the upper limit of the THz bandwidth: shorter pulses give broader bandwidth. The tunable optical parametric amplifier (OPA) provides an optical pump with adjustable wavelength - used to photoexcite charge carriers in the sample and so change the transmitted - reflected and/or emitted THz signal. A ratio of the laser power is thus used for THz generation - while the rest is used at the OPA. Because the absorption depth depends on wavelength - tuning the pump makes it possible to excite carriers at controlled depths. The system will be...