Recent advances in terahertz imaging

We review recent progress in the field of terahertz "T-ray" imaging. This r elatively new imaging technique, based on terahertz time-domain spectroscop y, has the potential to be the first portable far-infrared imaging spectrom eter. We give several examples which illustrate the possible applications o f this technology, using both the amplitude and phase information contained in the THz waveforms. We describe the latest results in tomographic imagin g, in which waveforms reflected from an object can be used to form a three- dimensional representation. Advanced signal processing tools are exploited for the purposes of extracting tomographic results, including spectroscopic information about each reflecting layer of a sample. We also describe the application of optical near-field techniques to the THz imaging system. Sub stantial improvements in the spatial resolution are demonstrated.