Comparison of phase-sensitive imaging techniques for studying terahertz waves in structured LiNbO3

Four phase-sensitive imaging methods (Talbot, phase contrast, Sagnac, and polarization gating) used for detecting terahertz-frequency waves in structured lithium niobate slabs are compared analytically and experimentally. It is demonstrated that both phase contrast and a self-compensating polarization gating geometry can generate in-focus images of the sample and quantitatively measure the terahertz electric field. Of these two methods polarization gating has better signal-to-noise ratio and so is preferred for most situations, while phase contrast imaging has better spatial resolution and so is preferred for measurements involving fine structures or near-field effects. (C) 2010 Optical Society of America