We present a combined quantum ghost and scanning imaging protocol allowing 2D imaging with 1D detector array, enabled by strong spatial correlations and tunable emission angle of entangled photon pairs emitted from ultrathin nonlinear metasurfaces.
We demonstrate experimentally that a strongly enhanced generation of spatially entangled photon pairs can be achieved from metasurfaces supporting nonlocal double resonances at the signal and idler wavelengths, and reveal that multiplexed metagratings featuring different orientations allow the engineering of bi-photon polar-ization states and optically controllable generation of arbitrary polarization qutrits. Furthermore, leveraging the exceptional capabilities of the metasurface, we present a combined quantum ghost and scanning imaging protocol allowing 2D imaging with a 1D detector array.
Nonlinear optical metasurfaces, which relax the phase-matching constraints of bulk nonlinear crystals and allow for precise engineering, are opening new possibilities in the field of quantum photonics. Recent advancements have experimentally demonstrated high-resolution 2D imaging using a 1D detector array by combining quantum ghost imaging and all-optical scanning with spatially entangled photon pairs generated from a nonlinear metasurface. These findings establish metasurfaces as a promising platform for quantum imaging, communications, and sensing applications.
The quantum correction of photon pairs inspired the development of quantum ghost imaging principles. It offers fundamental advantages compared to conventional imaging, including the operation at ultra-low photon flux and the potential for higher resolution [1]. Over the last year, it was demonstrated experimentally that nonlinear metasurfaces with a thickness of only a few hundred nanometers can facilitate strongly enhanced generation of photon pairs through spontaneous parametric down-conversion (SPDC). Furthermore, the quantum photon state can be tailored to feature spatial [2] and spectral [3] entanglement. However, the potential of metasurface-based photon-pair sources for quantum imaging was not previously investigated.
Abstract Nonlinear metasurfaces with subwavelength thickness were recently established as versatile platforms for the enhanced and tailorable generation of entangled photon pairs. The small dimensions and inherent stability of integrated metasurface sources are attractive for free-space applications in quantum communications, sensing, and imaging, yet this remarkable potential remained unexplored. Here, we formulate and experimentally demonstrate the unique benefits and practical potential of nonlinear metasurfaces for quantum imaging at infrared wavelengths, facilitating an efficient protocol combining ghost and all-optical scanning imaging. The metasurface incorporates a subwavelength-scale silica metagrating on a lithium niobate thin film. Its distinguishing feature is the capability to all-optically scan the photon emission angle in the direction across the grating simply by tuning the pump beam wavelength. Simultaneously, the photon emission is broad and anti-correlated along the grating direction, allowing for ghost imaging. Thereby, we reconstruct the images of 2D objects using just a 1D detector array in the idler path and a bucket detector in the signal path, by recording the dependencies of photon coincidences on the pump wavelength. Furthermore, we theoretically demonstrate the quantum imaging of objects with an ultra-large field of view and improved imaging resolution. Remarkably, the corresponding number of resolution cells can exceed the performance of quantum ghost imaging with conventional bulky crystals by over four orders of magnitude. The demonstrated concept can be extended to multi-wavelength operation and other applications such as quantum object tracking, paving the way for advancements in quantum technologies using ultra-compact nanostructured metasurfaces.