Time Reversal Terahertz imaging

Terahertz (THz) research has received much attention recently. This development is due to the discovery of new THz-radiation sources and detectors such as quantum cascade lasers, photoconductive switches or electro-optic THz- detectors during the last decade. Of particular intereset are broadband Thz-spectroscopy and imaging systems operating in the frequency range 0.1-10THz. This paper describes a technique for imaging in the terahertz regime using time reversal of single cycle pulses. Specifically, the time-reversal symmetry of Maxwell’s wave equation is exploited to reconstruct the transmission function of a diffracting aperture by inverting the diffracted fields. After deriving a time-reversed form of the diffraction integral, it is demonstrated by simulation and experiment the reconstruction of one-(1-D) and two-dimensional (2-D) objects. A means to obtain data efficiently for reconstruction of 2-D apertures is described.