Far -infrared power detector with optical readout

In this paper, the authors report on a far-infrared power detector with an optical readout. Active element of such detector is an optical nonlinear crystal with a surface layer absorbing the electromagnetic waves. The absorbed energy changes properties of the crystal which is consequently detected by a probe optical beam. Operation principle of the detector we have verified on the detector functional model comprising the gallium-phosphide crystal with partially transparent metallic layer and using the terahertz quantum cascade laser emitting at 112 mum (2.7 THz) as a source. In addition, the results of study of the electro-optic detector were presented based on the quasi-phase matching between the probe light and terahertz wave that allows achieving unprecedented sensitivity for the terahertz field detection.