Fig. 1. Infrared photodetectors for multidimensional optical information acquisition

Fig. 2. MWIR（top）and LWIR（bottom）1280×720 images acquired by HRL ^［13］

Fig. 3. （a）Sequential mode of HgCdTe two-color infrared photodetector，（b）simultaneous mode of HgCdTe two-color infrared photodetector，（c）side view of HDVIP two-color photodetector，（d）top view of HDVIP two-color photodetector^{［24，25］}

Fig. 4. （a）Staggered structure of two-color infrared photodetector，（b）schematic of super-pixel four-color infrared photodetector

Fig. 5. （a）Structure of Van der Waals two-color photodetector，（b）simulated energy band diagram with p-Si under a negative voltage，（c）normalized spectral response of the two-color photodetector during the back radiation，（d）structure of Quantum dot two-color photodetector，（e）energy band under 0 V bias of two-color photodetector，（f）optical absorption diagram^{［32，33］}

Fig. 6. （a）Single-nanowire spectrometers，（b）schematic of photodetector^［34］

Fig. 7. （a）Traditional infrared image，（b）polarization image，（c）visible image，（d）traditional infrared image，（e）polarization image^{［35，36］}

Fig. 8. Common types of infrared polarization imaging

Fig. 9. （a）Selection mode of Photo state polarization，（b）Polarization selection mode of subband transition law，（c）extinction ratio line^{［43，44］}

Fig. 10. （a）Schematic of the nanoantenna-mediated semimetal photodetector，（b）calculated PRs as a mapping of（θ1，θ2）values，（c）cutline plot of the PRs along the dashed line in b，（d）schematic of MSM to sense the linear（left）or circular（right）polarization states，（e）band diagram under bias^{［46，47］}

Fig. 11. Current intensity response of ReSe₂ photodetectors under different light polarizations^［48］

Fig. 12. （a）Metasurface-mediated graphene photodetector，（b）the experiment diagram of controlling the linear polarization state，（c）simulation diagram of vectorial photocurrent，（d）ploar plot of measured I_ph，（e）the diagram of three-port device and polarization 2D plot^［53］

Fig. 13. Schematic of Direct Time of Flight（DTOF）and traditional Avalanche Photodiode（APD）

Fig. 14. （a）BP/InSe heterostructure，（b）the noise of APD，（c）traditional ionizing collision process，（d）ballistic avalanche of BP/InSe heterostructure^［65］

Fig. 15. （a）Schematic diagram of MIM cavity，（b）transmission of MIM cavity with varying the polarization of incident light，（c）structure diagram of tapered InP nanowires APD，（d）simulated absorption^［69］

Fig. 16. New single photodetectors of nanowire^［70］

Fig. 17. （a）Structure diagram of 3D/2D heterojunction，（b）schematic of 3D/2D heterojunction，（c）schematic of heterojunction，（d）schematic of staircase APD structure ^［71-74］

Fig. 18. （a）Schematic of semi-ring plasmonic nano-slit，（b）diagram of on-chip plasmonic nanogratings，（c）OAM light with different topological charges is converted to different SPP waves^{［81，82］}

Fig. 19. （a）Left：schematic and SEM image of the phase modulation OAM beam splitter，right：scattered intensity profiles of the device for incident beams with different angular momentum，（b）schematic of the plasmonic spin-Hall nanograting，（c）schematic illustration and simulated results for determining the optical singularities by the spin-multiplexed metasurface，（d）schematic for determination of free space optical singularities^{［83，84，88，89］}

Fig. 20. Summary of new materials，new structures，new concepts and development prospects of next generation infrared detectors

Table 1. Advantages of two-color infrared photodetector in military application

Table 2. Comparison of two different modes of two-color infrared detectors