Grant: Alliance Grants

Terahertz (THz) imaging and spectroscopy are fast-growing fields of research and development with target applications in medicine, security, and product quality control. These applications take advantage of unique properties of THz radiation: It can be transmitted through cardboards, polymers, and other materials opaque in the visible region. Plus, it interacts with a large range of molecular vibrations, thereby enabling the detection and identification of bacteria in food supply chains, expired drugs in pharmaceutical, or toxic chemicals in suspicious packages. However, the long wavelength of THz radiation limits its ability to resolve sub-millimeter size features, which considerably hinders its range of imaging applications. THz quantum ghost imaging offers the possibility to benefit from the unique properties of THz waves while the spatial resolution is set, in part, by an entangled visible photon. However, this technique requires a detector capable of resolving single terahertz photons. This proposal focuses on the development of such a device. Current state-of-the-art sensitive detection techniques rely on bulky and costly apparatus, such as thermally-sensitive superconductors, which are hardly scalable due to their cryogenic equipment requirement. Our concept is based on a practical room-temperature design utilizing a combination of photonic techniques recently demonstrated by the two academic applicants and the National Research Council Canada. The general idea is to shift the frequency of a single THz photon into the visible region through an efficient nonlinear upconversion process. This collaboration with TeraXion will allow seamless integration of this nonlinear technology into fiber-based optical systems involving a low-noise laser cavity and customized Bragg gratings to reach optimal detection efficiency with minimal parasitic noise. Commercially-available single-photon detectors will then be integrated into the device to resolve upconverted photons carrying the original THz information. Other quantum applications will also be explored during this project for wireless communication cryptography and characterization of quantum materials.