A tapered parallel-plate-waveguide probe for THz near-field reflection imaging

We demonstrate a broad-band low-loss THz near-field imaging technique based on a tapered parallel-plate waveguide. This technique works in a reflection geometry, which avoids the problem of low energy throughput due to the impedance mismatch and consequently limited spatial resolution, in the transmission geometry. Images reconstructed by the filtered-back-projection algorithm are able to resolve features of size ∼100 μm using radiation with an average wavelength of 1.5 mm.