THz spectroscopy based on high-speed ASOPS

Asynchronous optical sampling (ASOPS) is a method for ultrafast time-domain spectroscopy that operates without mechanical delay generators that are common to conventional approaches. This is the central prerequisite for a massive reduction of data acquisition time and permits time-domain spectroscopy at the shot-noise limit without additional measures for suppression of technical noise. Mediated through the use of femtosecond lasers with 1 GHz repetition rate, ASOPS can be performed with a time-resolution close to 100 fs. This high-speed ASOPS approach is ideally suited for terahertz time-domain spectroscopy at frequencies ranging from approximately 100 GHz to a few THz. Here, we discuss a THz time-domain spectroscopy system based on high-speed ASOPS with 3 THz bandwidth and 1 GHz frequency resolution that delivers high dynamic range spectra within just 1 s of averaging time.