Cavity based THz photoconductive switches: real time THz imaging

Optically-driven photoconductive switches are one of the predominant sources currently used in terahertz imaging systems. However, owing to their low average powers, only raster-based images can be taken, resulting in slow acquisition times. In this work, we show that placing a photoconductive switch within a cavity, we are able to generate absolute THz powers of 181 µW. The cavity is based on a metal-insulator-metal structure that permits an enhancement of the average power by almost one order of magnitude whilst conserving a broadband response. We demonstrate real-time imaging using this source, with the broadband spectrum permitting to eliminate diffraction artefacts.