Cavity-based Terahertz Photoconductive sources for Real-Time Terahertz 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 by placing a photoconductive switch within a metal-metal cavity, we generate absolute average THz powers of 181 μW. The structure permits an enhancement of the average power by almost one order of magnitude compared to a standard structure, whilst conserving a broadband spectral response. We demonstrate real-time THz imaging using this source, with the broadband spectrum permitting to eliminate strong diffraction artefacts.