Flexible photonic metastructures for tunable coloration

The ability to actively control the perceived color of objects is highly desirable for a variety of applications, such as camouflage, sensing, and displays. We report a completely new flexible, high-contrast metastructure (HCM) whose color can be varied by stretching the membrane. This is accomplished by annihilating the 0th order diffraction while enhancing the -1st order, a new phenomenon made possible with a large index contrast. The color perception of the HCM can thus be changed by varying its period. The structure is fabricated using silicon metastructures embedded in a flexible membrane. We experimentally demonstrate brilliant colors and change the color from green to orange (39 nm wavelength change) with a stretch of 25 nm period change. The same effect can be used for steering a laser beam, with more than 36 resolvable beam spots being demonstrated.