Far -infrared power detector with optical readout

An electro-optic detection of the coherent free space terahertz waves has boosted the development of the terahertz technology [1]. Unlike other THz detectors, this detector type operates at room temperature and utilizes an electric field induced birefringence of the optical crystal. Induced birefringence can be monitored by an ultrashort near-infrared pulse and provides information about the instant vector of the THz electric field [2], so highly sensitive terahertz detection at room temperature is achievable in principle. In recently presented measurement of the terahertz quantum cascade laser output power in the CdTe electro-optic crystal is obtained from directly sampled electric field of the laser coherent radiation [3], but little attention was paid to responsivity of the used electro-optic crystal. Therefore, optimization of the detector concept has to be performed.