红外双光子探测与成像技术研究进展 (特邀)

Significance Infrared detection and imaging play important roles in space communication, remote sensing, spectroscopic analysis, and biomedical diagnostics. In emerging scenarios such as weak-signal sensing, high-temporal-resolution measurements, and multidimensional information acquisition, increasingly stringent requirements are imposed on detection sensitivity and system stability. However, conventional linear infrared detectors based on narrow-bandgap semiconductors suffer from high dark noise, strong reliance on cooling, and high array fabrication costs at room temperature, which limit their further development in high-sensitivity, large-field-of-view, and multi-pixel imaging applications. Infrared detection and imaging technologies based on semiconductor two-photon absorption introduce a nonlinear carrier-generation mechanism in wide-bandgap materials, enabling indirect electrical responses to sub-bandgap infrared photons. This approach allows mature silicon-based detector platforms to achieve infrared sensitivity at room temperature while maintaining low dark noise and high stability, and can be directly integrated with high-pixel-density array devices, providing a new physical pathway toward low-noise, wide-field, parallel infrared detection and imaging systems. Progress Starting from the fundamental physical mechanisms of infrared two-photon absorption detection, this paper systematically reviews the major operation regimes, including degenerate, nondegenerate, and extreme nondegenerate two-photon absorption, and discusses their technological evolution. Early studies mainly relied on degenerate two-photon absorption, where high peak intensities were used to generate carriers for nonlinear parameter measurements and feasibility demonstrations of infrared response. However, the strong dependence on instantaneous optical intensity limited its practical potential under weak-signal and large-field-of-view conditions. With the introduction of auxiliary pump fields, nondegenerate two-photon absorption schemes significantly reduced the required signal intensity through the cooperative absorption of infrared signal and pump photons, while extending the detectable spectral range. The subsequently developed extreme nondegenerate mechanisms, benefiting from near-resonant virtual-state transitions, further enhanced the effective absorption efficiency, enabling improved room-temperature detection of weak infrared signals. Based on these mechanisms, infrared two-photon absorption has gradually evolved into an independent infrared detection route with distinct advantages. This approach directly maps infrared optical information into carrier signals within wide-bandgap semiconductors, offering room-temperature operation, low dark noise, and broad spectral coverage. Leveraging mature semiconductor platforms such as silicon, it can be readily integrated with high-performance visible-band readout devices to realize large-scale array detection with high stability. Meanwhile, the introduction of alternative material systems, including InGaAs, GaN, and perovskites, further enhances infrared response strength and system sensitivity, providing diverse implementation pathways for different spectral regions and application scenarios. In recent years, infrared two-photon absorption has expanded from single-point detection to spatial imaging. Scanning-based imaging using single-pixel detectors exploits the intrinsic temporal gating and nonlinear intensity dependence of two-photon absorption to achieve high-contrast infrared imaging under weak-signal and strong-background conditions. With the advancement of array detectors, CCD, CMOS, and InGaAs focal-plane arrays have been incorporated into the two-photon absorption process, enabling wide-field infrared imaging at room temperature without cryogenic cooling, and significantly improving imaging efficiency and system stability. Furthermore, by integrating computational imaging concepts, two-photon-absorption-based single-pixel imaging realizes spatial encoding and nonlinear detection directly at the detector, effectively alleviating the limitations of mid-infrared spatial modulators and the high cost of array detectors. Owing to its intrinsic ultrafast temporal gating and nonlinear response, infrared two-photon imaging has also been extended to three-dimensional tomographic and spectrally selective imaging, enabling the simultaneous acquisition of structural and chemical information. Conclusions and Prospects Overall, infrared two-photon-absorption-based detection and imaging have evolved from early demonstrations of nonlinear physical concepts into a new class of infrared sensing technologies featuring room-temperature operation, high sensitivity, and multidimensional information acquisition. By eliminating the need for cryogenic cooling, simplifying system architectures, and leveraging mature silicon-based detector platforms, this approach provides an alternative pathway for weak infrared signal detection and imaging beyond conventional linear schemes. In the future, through the co-optimization of material systems, wavelength configurations, and device architectures, together with the integration of computational imaging and intelligent reconstruction strategies, it is expected that efficient multidimensional information acquisition can be achieved while maintaining system simplicity, thereby advancing the technology from laboratory demonstrations toward practical infrared detection and imaging platforms.