Fig. 1. The schematic diagram for the nanophotonic pixel matrix, controlled with an FPGA and computer.

Each matrix pixel has a cavity consisting of a metal reflective layer and a VO₂ layer laid on top of the microheaters made of ITO. The top-left inset shows an enlarged view of a single VO₂ pixel, with side lengths of l₁ and l₂, VO₂ thickness of $t_{{\mathrm{VO}}_2}$, ITO thickness of t_ITO, Ag thickness of t_Ag and SiO₂ thickness of $t_{{\mathrm{SiO}}_2}$. For colour generation of the nanophotonic matrix (i), the electrically programmable matrix is controlled through the row–column scheme, and the entire device works in the refresh mode for display. For spectrum detection of the nanophotonic matrix (ii), each unit spectral pixel consists of 2 × 2 VO₂ cavities integrated onto a single heater, which is controlled individually. Every pixel can be regulated to any intermediate state at any time. The black solid boxes in the figure show the optical microscope images of the pixels, and the red dashed boxes show illustrations for display and spectrum detection. Ins., the insulating state; Met., the metallic state. Scale bars, 100 µm in (i) and (ii).