Two-dimensional imaging and three-dimensional reconstruction of low reflectivity surfaces by using the range-gating upconversion second-harmonic method

Coherence-based imaging through turbid media by use of degenerate four-wave mixing in thin liquid-crystal films and photorefractives

We describe a coherence-based imaging technique based on degenerate four-wave mixing in two materials. First, a 45 degrees -cut BaTiO(3) crystal was used as a self-pumped phase conjugator to obtain depth-resolved images through a 4 mean-free-path (mfp) scattering media. In addition, an HITC dye-doped K15 liquid-crystal layer was used to provide single-shot image acquisition through a 2 mfp scattering media. This technique can be used to provide instantaneous (single-pulse), depth-resolved, two-dimensional images of the internal structure of scattering materials. Potential applications of this technique include subsurface imaging of biomedical tissue and nondestructive evaluation of composite materials.