Metamaterials to see in terahertz in “colors”

We report real-time, multi-spectrally selective terahertz (THz) imaging using multi-spectral metamaterial focal plane arrays (MM-FPAs) that are fully compatible with standard micro-electro-mechanical systems (MEMS) processes. A set of frequency switchable quantum cascade lasers (QCLs) is used as THz sources for multi-spectral illumination. Both MM-FPAs and QCLs can be readily tuned to operate at multiple discrete THz frequencies to match the “fingerprints” of the analytes. Frequency selective material identification of concealed substances are successfully demonstrated, which promises a great potential of this technique in security sensing applications.