Two-Photon Imaging with Entangled and Thermal Light

Abstract

Two‐photon “ghost” imaging, based on the second‐order intensity correlation, was first realized with entangled light, but has now been demonstrated with true thermal light. Following our work on lensless and high‐order ghost imaging with thermal light, we have recently shown that both entangled and thermal light may be used to produce two‐photon correlation Talbot effects. In the Talbot effect, first observed in 1836, a periodic object illuminated with coherent light can give rise to repeated self‐images at specific positions within the Fresnel diffraction field without any lens. Using an incoherent thermal light source, we have experimentally observed second and higher order Talbot self‐images, including fractional and phase‐reversal images, at multiples of the Talbot length in a lensless setup containing two optical paths. We have also recently observed another surprising imaging phenomenon which does not depend on the second‐order correlation function, and can produce both negative and positive images of a nonlocal object. It is expected that these types of imaging will find novel applications in both the microscopic and macroscopic regimes.