Terahertz Spectroscopic Imaging with Nonlinear Quantum Cascade Laser

A terahertz difference-frequency generation quantum cascade laser is a compact and ultra-broadband semiconductor source.An electrically pumped monolithic source is based on intra-cavity, difference-frequency generation and can be designed to achieve an ultra-broadband, multi-mode terahertz emission spectrum that extends from 1 to 4 THz without any external optical setup.We demonstrated spectroscopic imaging using a THz source.We performed spectroscopic imaging with frequency bandpass filters, and with this imaging technique, we clearly identified three different tablet components: polyethylene, D-histidine, and DL-histidine.This spectroscopic imaging technique may be suitable for the quality monitoring of pharmaceutical materials.