The system in Fig. 3a allows for the demonstration of these capabilities. Here, a laser source (532 nm) and goniometer allow motion of the laser beam in 3D coordinates, to provide incidence at any desired position. An automated measurement unit records the photoresponses of the 48 devices with ~64 Hz device interval (corresponding frame interval ~0.75 s), as in the bottom of Fig. 3a. The devices nearest to the location of illumination (entry or exit point) exhibit the highest photoresponses; those of the other devices decrease with increasing distance from this location owing to scattered light (Supplementary Fig. 16). Only the nine devices nearest to the illumination point respond significantly to the light signal; therefore, the position of the incident light is computed from the known coordinates of these nine devices (with respect to the center of the hemisphere). The calculation is according to1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{P}}_{\mathrm{I}}({\mathrm{\theta }}_{\mathrm{I}},{\mathrm{\varphi }}_{\mathrm{I}}) = (\mathop {\sum }\limits_1^9 (\theta _n \ast \frac{{I_{{\rm ph},n}}}{{\mathop {\sum }\nolimits^ I_n}}),\,\mathop {\sum }\limits_1^9 (\varphi _n \ast \frac{{I_{{\rm ph},n}}}{{\mathop {\sum }\nolimits^ I_n}})),$$\end{document}PI(θI,φI)=(∑19(θn*Iph,n∑nI),∑19(φn*Iph,n∑nI)),where PI is the spherical coordinate of the incident point, Iph is the photocurrent for the nth device, and θ and φ are the azimuthal and polar angles, respectively. As the laser beam moves, its trajectory can be recorded in this manner, as indicated by the arrow in Fig. 3b. From the initial point X1 (Fig. 3b), a continuous photoresponse spectrum immediately begins up to the final point X3. The responses of the nine nearest photodetecting devices in the recorded data define the location of the beam. Figure 3c shows the estimated positions of the beam (green dot) and the photoresponses of the nearest devices at three locations X1, X2, and X3 (Fig. 3b). These measured movements exactly match the laser movements, as indicated by the arrow (Fig. 3b). The device closest to the incident point delivers the maximum photoresponse (bright red point). Figure 3d shows the interpolated position of the incident laser beam corresponding to location X1 in spherical coordinates originating at the hemisphere center.Fig. 3Operating principles of a 3D photodetection and imaging system. a Schematic illustration and optical images of the system. Inset: magnified view. b Distribution of the devices and movement of the laser beam. c Photocurrent distribution on the hemisphere surface during movement of the laser beam. d Magnified view of the photocurrent distribution at the first position of the laser beam. The illuminating locations of the incident laser beam are estimated by interpolation. e Penetration of the laser beam at two points of the 3D hemispherical surface. f Photocurrent distribution on the hemisphere surface in the scenario of e. g Principle of estimating the incident direction of the laser from the photocurrent map