Solid state narrowband THz emitter

Numerous applications of THz systems have been demonstrated including imaging, nondestructive inspection and security screening. A major potential application of THz systems is in the spectroscopic analysis and detection of molecules through their fundamental absorption bands. Various polar molecules exhibit characteristic absorption lines arising from pure rotational transitions in the THz frequency region. Chemical substances such as illegal drugs or explosives show their characteristic absorption spectra at THz frequencies. Therefore, many gases, gas mixtures and chemical substances can be monitored by sensing and identifying their absorption spectra via THz spectroscopy. Here we propose a new method for efficient generation of broadly tunable THz waves, based on a comb of differential frequencies generation in a nonlinear crystal. Solid state lasers in doped photosensitive glasses will emit multiple equidistant frequencies controlled by volume Bragg gratings. Employing high intracavity intensities within a low-loss high Q resonator produced by extremely efficient VBGs will allow generating multi-mW powers in a wide range (1-5 THz) of THz frequencies.