We have developed several strategies for modulating the infrared absorptivity and emissivity of metasurfaces via electrical control signal. These employ such approaches as voltage-induced symmetry breaking and period doubling for controlling the coupling between a guided mode of the metasurface and the continuum. We further describe potential applications in encoding and encrypting light, for development of secure tags.
We explore the possibility of communicating encrypted information using infrared metamaterials. We first describe our algorithm for encrypting a plain image in multiple cipher images, each corresponding to a different wavelength channel. Our scheme is designed so that an interloper will not be able to recover the image from the summed intensity or the individual channels. However, the intended recipient can easily reconstruct the image by performing a mathematical operation over the channels. We implement this scheme in a 4-channel infrared metamaterial and demonstrate image encryption and decryption.
Thin-film Black Phosphorus (BP) has shown considerable promise as a material for mid-wave infrared photodetection. BP exhibits attractive materials properties that include a high photoresponse in the mid-wave infrared and an electrically tunable bandgap. However, bandgap tunability requires the material to be kept sufficiently thin, which limits the thickness, and therefore absorption, of a BP active layer in a photodetector. We have designed and characterized metamaterial gratings that increase the absorption in BP. We show that the metamaterial grating, when integrated into a photodetector, increases the photodetection capabilities of thin-film BP.
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