Fast Spectral Terahertz Imaging through Frequency Tuning in a Quantum-Cascade Laser

Abstract

Due to a variety of molecular rotational lines, spectroscopy in the terahertz (THz) spectral region is a powerful tool. It can be applied to detect and identify numerous chemical compounds in particular gases. Thus, it holds a large potential for a broad range of applications e.g. in astrophysics, medicine, and security. At present, THz imaging is realized with a variety of different techniques. However, relatively little work has been done regarding the combination of THz spectroscopy and imaging. In this contribution, we will present a QCL-based spectrometer that is capable of fast spectral imaging with a resolving power in the order of 10^6 and with high spatial resolution. The spectral information is obtained by tuning the frequency of the QCL. Frame rates of up to 3 Hz are realized by the combination of a fast scanning mirror (FSM) and a sensitive single-pixel Ge:Ga detector with a short response time.