PR37 An Alternative Strategy for Photon-Pair Generation using Integrated Photonics on Silicon Wafers (1640968-Y4)

Research activities include the design, fabrication and poling of a spontaneous parametric down-conversion (SPDC) waveguide in periodically-poled thin-film lithium niobate SPDC device, and measurements of photon-pair generation in it. Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 1640968 (Year 4).

Single-Pixel Imaging with Heralded Single Photons

Traditional remote sensing applications are often based on pulsed laser illumination with a narrow linewidth and characteristic repetition rate, which are not conducive to covert operation. Whatever methods are employed for covert sensing, a key requirement is for the probe light to be indistinguishable from background illumination. We present a method to perform single-pixel imaging that suppresses the effect of background light and hence improves the signal-to-noise ratio by using correlated photon-pairs produced via spontaneous parametric down conversion. One of the photons in the pair is used to illuminate the object whilst the other acts as a temporal reference, allowing the signal photons to be distinguished from background noise. This heralding method shows how the noise regime is key to producing higher contrast images.

Phase conjugation of twisted Gaussian Schell model beams in stimulated down-conversion

Stimulated parametric down-conversion is a nonlinear optical process that can be used for phase conjugation and frequency conversion of an optical field. A precise description of the outgoing stimulated field has been developed for the case where the input pump and seed fields are coherent. However, partially coherent beams can have interesting and important characteristics that are absent in coherent beams. One example is the twist phase, a novel optical phase that can appear in partially coherent Gaussian beams and gives rise to a nonzero orbital angular momentum. Here, we consider stimulated down-conversion for partially coherent input fields. As a case study, we use twisted Gaussian Schell-Model beams as the seed and pump beams in stimulated parametric down-conversion. It is shown both theoretically and experimentally that the stimulated idler beam can be written as a twisted Gaussian Schell-Model beam, where the beam parameters are determined entirely by the seed and pump. When the pump beam is coherent, the twist phase of the idler is the conjugate of that of the seed. These results could be useful for the correction of wavefront distortion such as in atmospheric turbulence in optical communication channels, and synthesis of partially coherent beams.