Surface profile measurement by terahertz interferometric phase imaging

We demonstrate an interferometric phase imaging technique by using a continuous-wave terahertz system with a far-infrared gas laser as the radiation source. A terahertz Michelson interferometer is constructed based on a reflection imaging system. By analyzing the measured fringe patterns, the phase distribution information can be obtained and then used to reconstruct the profile of the object surface under test. We also show that, for imaging a nearly transparent object with terahertz radiation, our technique can provide a high contrast image which would be quite valuable for accurate identification of the examined object.