Interferometric imaging with terahertz pulses

摘要

We demonstrate a new reflection imaging technique usingnsingle-cycle pulses, in which the sample to be imaged is placed at thenfocus of a lens in one arm of a Michelson interferometer. The detectednsignal is the superposition of the pulses from the two arms of theninterferometer, one with a sample and one with a reference mirror.nBecause of the Gouy phase shift from the lens in the sample arm, thesentwo pulses are nearly Π out of phase, and can destructivelyninterfere. This leads to a strong cancellation of the measured waveformnand a nearly background-free imaging method. We demonstrate thentechnique using terahertz time-domain spectroscopy and show that thendestructive interference provides enhanced sensitivity to features innthe sample that are much thinner than the coherence length of thenradiation. This technique could be valuable in any low-coherencentomographic measurement in which the reflected electric field can benmeasured directly