Patent ID: 6734974
Filing Date: 2004-05-11
Classification: G01N,G02F

Abstract:
A system for using terahertz (THz) radiation to produce an image of an object, the system comprising:means for providing an optical pump pulse, an optical probe pulse having a polarization ellipticity, and an optical gating pulse with a variable delay time between the optical pump pulse and the optical probe pulse; a THz emitter for emitting a beam of THz radiation when activated by the optical pump pulse; means for chopping the optical gating pulse on and off; a layer of semiconductive material comprising (a) a part of the object, or (b) a discrete layer positioned between the object and the THz radiation; means for focusing the optical gating pulse and the THz radiation on the layer of semiconductive material so that the gating pulse illuminates a gating pulse focal spot on the layer of semiconductive material, the gating pulse focal spot having a diameter effective to cause measurable modulation in transmission of the THz radiation through the layer of semiconductive material when the gating pulse is on as compared to when the gating pulse is off, creating alternating modulated THz beams; a THz receiver, positioned to receive the alternating modulated THz beams reflected from or transmitted through the object, for modulating the optical probe pulse with the alternating modulated THz beams to create corresponding modulation in the optical probe pulse polarization ellipticity; means for converting the modulation in the optical probe pulse polarization ellipticity to intensity modulation in the optical probe pulse; means for converting the intensity modulated optical output pulse to electronic information; and means for receiving the electronic information and producing an image of the object from the electronic information.