Fast terahertz computed-tomography imaging with a quantum-cascade laser and a scanning mirror

A terahertz transmission imaging system based on a quantum-cascade laser (QCL), a fast scanning mirror, and a sensitive Ge:Ga detector is demonstrated. In order to reduce artifacts, special care was taken on the optics and the conversion of the measured data into the image. Images with a diameter of approximately 40 mm and a signal-to-noise ratio of up to 28 dB were obtained within 1.1 s. The system was used to record three dimensional images of objects in an ellipsoidal volume with axes of approximately 40 mm by computed tomography within 87 s. In addition to the Ge:Ga detector, a more compact pyroelectric device was also used for detection.