High-speed ASOPS based THz time-domain spectrometer

High-speed asynchronous optical sampling with two offset-locked Ti:sapphire femtosecond oscillators permits time-domain THz spectroscopy with almost 7 THz bandwidth at 1 GHz resolution. The system operates at 2 kHz scan rate without moving mechanical parts. The mean fractional frequency error of absorption lines in a measured water vapor absorption spectrum with respect to the data published in the HITRAN database is 5.9times10^-5, the maximum fractional error is 2.1times10^-4. The system´s potential for rapid sensing applications is demonstrated by reading out a frequency selective surface sensor with an uncertainty of 210 MHz within only 2 s of acquisition time.