Spectroscopic imaging with a compact terahertz difference frequency generation source

We demonstrate spectroscopic imaging using a compact ultra-broadband terahertz source with a high-power, mid-infrared quantum cascade laser. The electrically pumped monolithic semiconductor source is based on intra-cavity difference-frequency generation and can be designed to achieve an ultra-broadband multi-mode terahertz emission spectrum extending from 1 to 4 THz without any external optical setup. We acquired false-color R, G, and B image, and as a result, this imaging technique clearly identified three different tablet components (polyethylene, D-histidine and DL-histidine). This method may be highly suitable for quality monitoring of pharmaceutical materials.