Interference between two coherently driven monochromatic terahertz sources

We report the interference between two phase-locked, continuous-wave, and coherent terahertz (Thz) photomixers. Both spatial and temporal coherence are observed with a narrow linewidth of less than 10 MHz. Phase locking is achieved by using one pair of lasers for both sources. The concept of optical narrow linewidth (fiber) distribution of the mixing signal opens various applications. We outline the necessary steps to extend this scheme for very long base line interferometric THz detection in the tens of kilometer range and for the improvement of spatial resolution for active stand-off THz imaging. (C) 2008 American Institute of Physics