Continuous-wave terahertz diffraction tomography

We implement diffraction tomography using a continuous-wave terahertz (CW-THz) source. An off-axis digital holographic interferometry system was built to measure the complex amplitude distributions of a sample for various rotation angles. Based on the Rytov approximation, the three-dimensional (3D) refractive index (RI) distributions of the polystyrene foam spheres was reconstructed by the filtered backpropagation algorithm.