Tunable graphene-based infrared reflectance filter having patterned nanoantenna layer and unpatterned graphene layer
| DWPI Title: Tunable graphene-based infrared reflectance filter, e.g., for infrared detector, has nano-antenna layer which is patterned to excite plasmons with graphene layer and applies voltage to graphene layer to change Fermi level of graphene |
| Abstract: An actively tunable optical filter can control the amplitude of reflected infrared light. The filter exploits the dependence of the excitation energy of plasmons in a continuous and unpatterned sheet of graphene, on the Fermi-level, which can be controlled by conventional electrostatic gating. An exemplary filter enables simultaneous modification of two distinct spectral bands whose positions are dictated by the device geometry and graphene plasmon dispersion. Within these bands, the reflected amplitude can be varied by over 15% and resonance positions can be shifted by over 90 cm−1. Electromagnetic simulations verify that tuning arises through coupling of incident light to graphene plasmons by a nanoantenna grating structure. Importantly, the tunable range is determined by a combination of graphene properties, device structure, and the surrounding dielectrics, which dictate the plasmon dispersion. Thus, the underlying design is applicable across a broad range of infrared frequencies. |
| Use: Tunable graphene-based infrared reflectance filter, e.g., for infrared detector. |
| Advantage: The filter avoids patterning of the graphene itself and prevents contact between graphene and metal structures, avoiding Fermi level pinning of the graphene that limits spectral tunability. The nano-antenna can act as the primary gate for graphene allowing the high-k dielectric nature of hafnium dioxide to be employed for injection of charge into the graphene. Field enhancement within the small gaps of the nano-antenna results in increased interaction of incident light with the continuous graphene sheet. The resonant response of the nanoantenna itself excites graphene plasmons that can dominate the overall response of the filter. By selecting cladding dielectrics based on their phonon modes, the tuning range can be designed. The use of unpatterned large-area graphene ensures the scalability of the design reducing the complexity inherent in fabrication. The filter can be further improved through use of higher quality graphene. Enables frequency agile solid-state filters than can provide hyperspectral infrared sensing without the necessity for modification of the detector itself. |
| Novelty: The tunable graphene-based infrared reflectance filter has a bottom dielectric layer on a substrate. A graphene layer is on the bottom dielectric layer. A top dielectric layer is on the graphene layer. A conductive nano-antenna layer on the top dielectric layer is patterned to excite plasmons within the graphene layer. The nano-antenna layer is also adapted to apply a voltage bias to the graphene layer, changing the Fermi level of the graphene and tuning the resonance response of the filter to incident infrared light. The nano-antenna layer comprises conductive oxide, metal, polymer, or non-conductive metal. |
| Filed: 1/16/2018 |
| Application Number: US15872293A |
| Tech ID: SD 14291.0 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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