30 September 2015 Photoconductively excited plasmonic modulator-switch
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A novel plasmonic modulator-switch for the long-wave infrared (LWIR) region is presented. The device consists of a thin metal film, an underlying photoconductive substrate, input and output reflection gratings located on top of the film on opposite ends of the device, and a limited aperture detector located over the out-couple grating. LWIR incident at a given angle is in-coupled, generating surface plasmons (SPs). Since the underlying metal film is thinner than the SP penetration depth, the SPs are couple on both the top and the bottom of the thin film and propagate on both sides of the metal film toward the out-coupling grating. When free carriers in the photoconductive substrate are excited by laser illumination, the electrical properties of the substrate are changed. This change in substrate electrical properties is sensed by the propagating SPs and thus changes the wavevector of the SPs. The SP wavevector change will cause the out-coupled radiation magnitude and angle to change. Thus, the radiation incident on the detector is modulated implementing a plasmonic modulator-switch. Full-wave electromagnetic simulations were performed on the device. The reflected power at various angles was calculated for a fixed incident angle at λ = 10 μm using various geometries and substrate materials. The substrate materials modelled include III-V compound semiconductors and Si. The dielectric functions for these materials were computed as functions their free carrier concentration to simulate excited and unexcited states. This paper reports on how device performance was affected by variation of these geometric and material parameters.
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John S. Cetnar, John S. Cetnar, David E. Zelmon, David E. Zelmon, David H. Tomich, David H. Tomich, } "Photoconductively excited plasmonic modulator-switch", Proc. SPIE 9547, Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, 95472D (30 September 2015); doi: 10.1117/12.2185229; https://doi.org/10.1117/12.2185229

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