Fast Screening System

Terahertz intensity measurements at unprecedented speed

Certain applications in quality control and process monitoring that require no spectral information, but call for terahertz intensity measurements at “extreme” speeds. The combination of a femtosecond fiber laser, a pulsed terahertz emitter and a high-bandwidth Schottky receiver yields a setup capable of detecting individual terahertz pulses, even at repetition rates as high as 100 MHz. To handle this immense data stream, a data-processing unit converts the pulses to RMS values, producing terahertz intensity readings at sampling rates up to 500 kHz – orders of magnitude faster than any conventional terahertz system.

In a way, the system represents the world’s fastest single-pixel terahertz camera. In order to generate a terahertz transmission or reflection image, one can complement the system with fast beam-steering optics. In another application scenario, the samples themselves move – e.g. on a fast conveyor belt, or as part of a papermaking machine. In this use case, emitter and receiver remain static, and the data stream yields line scans with high spatial resolution, even for sample velocities beyond 100 m/s.