Optical pump-terahertz probe spectroscopy utilizing a cavity-dumped oscillator-driven terahertz spectrometer

A terahertz spectrometer capable of steady-state and time-resolved measurements over the 0.1-3.5-THz spectral region has been built. This spectrometer routinely produces and detects terahertz pulses that exhibit signal-to-noise ratios (SNRs) greater than 6000 in the time domain and a spectral noise door of magnitude 2.7/spl times/10/sup -4/. Hence, the spectrometer achieves nearly four decades of dynamic range in the frequency domain. Two pulse generation processes are observed to give rise to the measured terahertz pulse. High-quality optical pump-terahertz probe data on <111> GaAs samples are presented, demonstrating the applicability of this spectrometer to the study of optically induced dynamical processes. Non-Drude relaxation behavior is observed in the transient terahertz spectra.