Multi-wavelength ghost imaging: a review
Ghost imaging (GI) forms images from intensity-correlation data collected by a single-pixel detector, decoupling illumination and sensing. Since its quantum-photon origins, the technique has evolved through classical pseudothermal, computational and deep-learning variants to span an unprecedented spectral range--from extreme-ultraviolet (XUV) to terahertz (THz) waves and even matter waves. This review traces that evolution, highlighting how wavelength dictates modulators, detectors and propagation physics and, in turn, the attainable penetration depth, resolution and dose. We survey X-ray/XUV implementations that deliver low-damage microscopy, visible/near-IR systems that achieve video-rate lidar through fog and water, mid-IR platforms that extract molecular fingerprints in photon-starved conditions, and THz schemes that provide non-destructive inspection of concealed structures. These advances collectively position multi-wavelength GI as a versatile, low-dose alternative wherever conventional focal-plane arrays falter.