Time-domain terahertz spectrometer based on high-speed asynchronous optical sampling

We present a terahertz time-domain spectrometer with large bandwidth, high spectral resolution, and high sensitivity. A bandwidth of larger than 3 THz, a resolution of 1 GHz and a sensitivity of larger than 60 dB dynamic range are achieved in a data acquisition time of less than 60 s. The spectrometer is based on high-speed asynchronous optical sampling which employs two femtosecond lasers of 1 GHz repetition rate stabilized to 10 kHz off-set of the repetition rates employing a 3 GHz frequency shifter. This technique opens new perspectives to perform high-resolution THz spectroscopy under rapidly varying environmental conditions.