Fourier pixels for bidirectional light control
Digital cameras1 and displays2 use picture elements (pixels3) that perform a single function: detecting or emitting light intensity. To exploit the full information content of electromagnetic waves, more advanced elements are required. This has driven the development of multifunctional components that, for example, simultaneously detect and emit intensity4,5 or extract intensity and spectral information6–8. However, no pixel exists that both senses and generates optical wavefronts with full control over amplitude, phase and polarization, limiting bidirectional control and feedback of sophisticated light fields. Here we present a route to such pixels by demonstrating a versatile platform of miniaturized diffractive elements based on Fourier optics9. We use plasmonic surface waves10, which propagate coherently11 and efficiently12–15 across metallic surfaces. When these plasmons are launched towards wavy microstructures16 designed with simple Fourier analysis, arbitrary and background-free optical wavefronts are generated. Conversely, incoming light can be sensed, and its amplitude, phase and polarization can be fully characterized. By combining or superposing several such components, we create multifunctional ‘Fourier pixels’ that provide compact and accurate control over the optical field. Our approach, which we extend to photonic waveguide modes, establishes a scalable, universal architecture for vectorially programmable pixels with applications in adaptive optics17,18, holographic displays19–21, optical communication22,23 and quantum information processing24. A versatile platform of miniaturized Fourier-optics-based diffractive elements enables multifunctional pixels that fully control and sense the amplitude, phase and polarization of optical wavefronts for advanced photonic applications.