Metamaterial based wideband infrared absorbers

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Elektrik ve Elektronik Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: KADİR ÜSTÜN

Danışman: GÖNÜL SAYAN

Özet:

In this thesis, design and simulation of wideband metamaterial absorbers are investigated in the long wave infrared (LWIR) and the mid-wave infrared (MWIR) bands of the electromagnetic spectrum. Use of LWIR and MWIR bands in absorber design is especially important for critical applications including the design of thermal cameras and thermal emitters. Integration of metamaterial topologies into the absorber structures provides flexibilities in design to enhance the operation efficiency of these devices by increasing both absorption levels and operation bandwidths. In this study, we have used different design approaches resulting in various thin metamaterial absorbers that can be fabricated by simple and low-cost optical lithography and yet display outstanding performances. One of the designs consists of two identical and parallel meta-surfaces embedded in a dielectric layer and a ground metal layer. This absorber achieves above 90 percent absorption almost over the whole LWIR region. Another absorber having the basic metal-dielectric-metal topology is based on broadening the absorption window by sculpturing a dispersive and lossy dielectric, silicon nitride. This absorber has covered almost complete LWIR region with at least 90 percent absorption level. Absorbers in the third group consist of a ground metal, a low-loss dielectric layer and a meta-surface, which is deliberately chosen to be a thin lossy metal layer to enhance absorption. These absorber structures are demonstrated to be very successful in the LWIR and MWIR bands. Especially in and around the MWIR band, nearly perfect absorption (at least 98.5 percent) is achieved over an almost octave bandwidth.