Gas absorption spectroscopy with electronic terahertz techniques

We report the first gas absorption spectra measured with an all-electronic terahertz spectrometer. This instrument uses phase-locked microwave sources to drive GaAs nonlinear transmission lines that produce picosecond pulses, enabling measurement of broadband spectra. By sweeping the fundamental excitation, the spectrometer can also measure single lines with Hertz-level precision, a new mode of operation not readily available with optoelectronic THz techniques. Since this system is based on integrated circuits, it could ultimately function as an inexpensive gas sensing system, e.g. for vehicle emissions.