Mid-infrared multidimensional upconversion imaging: Progress and prospects

Mid-infrared (MIR) imaging plays a pivotal role in chemical sensing, biomedicine, and material analysis, yet its further development is fundamentally constrained by limited room-temperature sensitivity and the lack of efficient multidimensional light-field control. In recent years, frequency upconversion imaging has emerged as a rapidly advancing approach that translates MIR signals to the visible or near-infrared domain, enabling high-sensitivity detection with mature, low-noise photonic platforms. More importantly, by engineering the pump field in nonlinear frequency conversion processes, a multidimensional imaging framework has been established, enabling indirect, all-optical encoding and retrieval of multiple degrees of freedom—including amplitude, phase, spectrum, time, and polarization—of MIR light fields. This paradigm shifts complex light-field manipulation from the MIR to technologically mature short-wavelength regimes, overcoming intrinsic limitations of conventional approaches. In this review, we systematically summarize the principles, architectures, and representative methodologies of MIR upconversion multidimensional imaging, and outline future directions toward high-sensitivity, high-dimensional, and integrated imaging systems, with implications extending to broader photonic and information processing domains.