Cost-effective THz spectroscopy with continuous-wave laser sources

We use a laser diode in an external cavity to operate a photomixer based terahertz spectrometer. The emission spectrum of the laser can be easily switched between two-color operation and multi-line operation by means of a specially designed end mirror. This changes the operation mode of the terahertz spectrometer from continuous wave operation to a scheme called terahertz quasi time-domain spectroscopy.