An electronic read-out circuit for time-domain terahertz imaging with photoconductive antennas.

We have developed a signal amplifier for the detection of weak repetitive pulsed signals superimposed on a large background. It is based on a double gated integrator principle with two channels locked to a sequence of alternate signal and background pulses. The circuit is compact and cost effective, and thus suitable for use in large numbers with detector arrays, for example in terahertz imaging. The performance was verified in terahertz time-domain spectroscopy based on an amplified femtosecond laser and found to be better than that of a commercial lock-in amplifier.