Time Gated Imaging Through Scattering Materials with Nonlinear Optical Raman Interactions

We have developed several time-gated imaging techniques that allow the viewing of objects through dense scattering material. These techniques are based on nonlinear optical Raman interactions and include pulse gating using stimulated Raman amplification and correlation gating using both coherent anti-Stokes Raman scattering and stimulated Raman scattering. In the ballistic imaging regime, images with resolution better than 125 μm have been obtained after scattering attenuations of up to e−33. We have performed theoretical studies to determine image resolution in the diffuse and quasi-diffuse scattering regimes. In the fully diffuse regime the spatial resolution is found to be approximately one-fifth of the length of the scatterer. We have verified this result experimentally. We have also used the above techniques to perform range-gated imaging of objects embedded in scattering and non-scattering material.