We design thermal emitters based on gold micrograting structures with VO2-filled slots for enhanced far-field thermal rectification. We numerically calculate the thermal rectification ratio for two different approaches, peak extinction and peak shift. In peak extinction, the VO2 phase transition switches the radiative coupling of the surface plasmon on and off. In peak shift, the phase transition shifts the wavelength of the radiatively-coupled surface plasmon. We vary the extinction coefficient of VO2 to determine the effect on rectification for each approach. In both cases, the rectification ratio can be increased by increasing the VO2 loss in the metallic state. This suggests that highly efficient, microstructured thermal rectifiers can be achieved via suitable manipulation of the optical properties of VO2.
We propose a gold nanostructured design for absorption enhancement in thin black phosphorus films in the 3–5 µm wavelength range. By suitably tuning the design parameters of a metal-insulator-metal (MIM) structure, lateral resonance modes can be excited in the black phosphorus layer. We compare the absorption enhancement due to the resonant light trapping effect to the conventional 4n2 limit. For a layer thickness of 5 nm, we achieve an enhancement factor of 561 at a wavelength of 4 µm. This is significantly greater than the conventional limit of 34. The ability to achieve strong absorption enhancement in ultrathin dielectric layers, coupled with the unique optoelectronic properties of black phosphorus, makes our absorber design a promising candidate for mid-IR photodetector applications.
The ability of metamaterials to manipulate optical waves in both the spatial and spectral domains has provided new opportunities for image encoding. Combined with the recent advances in hyperspectral imaging, this suggests exciting new possibilities for the development of secure communication systems. While traditional image encryption approaches perform a 1-to-1 transformation on a plain image to form a cipher image, we propose a 1-to-n transformation scheme. Plain image data is dispersed across n seemingly random cipher images, each transmitted on a separate spectral channel. We show that the size of our key space increases as a double exponential with the number of channels used, ensuring security against both brute-force attacks and more sophisticated attacks based on statistical sampling. Moreover, our multichannel scheme can be cascaded with a traditional 1-to-1 transformation scheme, effectively squaring the size of the key space. Our results suggest exciting new possibilities for secure transmission in multi-wavelength imaging channels.
The ability to tailor light–matter interactions using artificially engineered materials has opened up new avenues for secure data storage and communication. This work presents an experimental investigation of metasurfaces for secure, multi‐channel image encryption in the infrared (IR). The proposed metasurfaces consist of an array of pixels, each designed to produce a wavelength‐ and polarization‐dependent IR absorptivity. A basis set of pixels is designed for encrypting images of arbitrary resolution on a given number of wavelength and polarization channels. These pixels are fabricated, and their spectral response is experimentally measured using Fourier transform infrared spectroscopy. The measured data is used to emulate the encryption and decryption of binary and 8‐bit grayscale images. Finally, the security of the encryption scheme proposed in this work is evaluated by performing statistical analyses on the image data stored on different channels. The results presented in this study suggest intriguing possibilities for the development of encrypted tagging technologies in the infrared and thus have implications for secure object identification and anti‐counterfeiting.
We propose gold-vanadium dioxide microstructures for which the difference in thermally radiated power between the low and high temperature states can be tuned via structural design. We start by incorporating V O 2 in a gold-dielectric-gold waveguide to achieve a temperature-dependent mode effective index. We show that a cavity formed in this waveguide structure has a fundamental resonance wavelength that shifts with temperature. We calculate the thermal radiated power from the cavity at temperatures above and below the phase transition of V O 2 for wavelengths between 8 and 14 µm. We show that the difference in radiated power can be made positive, negative, or zero simply by adjusting the cavity length. Finally, we use our cavity to design thermally emissive metasurfaces with spatial emission patterns that can be inverted with temperature. Our emitters could serve as building blocks in the realization of metasurfaces enabling complex thermal radiation control.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.