OPTICAL PUMP-TERAHERTZ PROBE SPECTROSCOPY UTILIZING A CAVITY-DUMPED OSCILLATOR-DRIVEN TERAHERTZ SPECTROMETER

A terahertz spectrometer capable of steady-state and time-resolved mea surements over the 0.1-3.5-THz spectral region has been built. This sp ectrometer routinely produces and detects terahertz pulses that exhibi t signal-to-noise ratios (SNR's) greater than 6000 in the time domain and a spectral noise boor of magnitude 2.7 x 10(-4). Hence, the spectr ometer achieves nearly four decades of dynamic range in the frequency domain, Two pulse generation processes are observed to give rise to th e measured terahertz pulse. High-quality optical pump-terahertz probe data on [111] GaAs samples are presented, demonstrating the applicabil ity of this spectrometer to the study of optically induced dynamical p rocesses. Non-Drude relaxation behavior is observed in the transient t erahertz spectra.