Terahertz direct-contact refractometer/spectrometer.

A method for terahertz (THz) reflection spectroscopy is presented that utilizes direct contact between the backside of the pulsed emitter and the sample. Changes in the complex reflectivity of the emitter-sample interface are used to measure the spectrum. This method is especially useful for spectroscopy of liquid samples and soft materials. It simplifies the optical apparatus, has good sensitivity, and has capability for use in the construction of miniaturized THz probes. The problem of nonplanar wave fronts inside the emitter is discussed.