Metasurface microlens focal plane arrays and mirrors
Demir, Hilmi Volkan
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Lenses, mirrors and focal plane arrays (FPAs) are among the key components a ecting the functionality, performance and cost of electro-optical (EO) systems. Conventional lenses rely on phase accumulation mechanism for bending wavefront of light. This mechanism and the scarcity of transparent materials result in high-complexity, high-cost and bulky EO systems. Conventional mirrors, on the other hand, are limited by the electromagnetic properties of metals and cannot be used in certain EO systems. Also, conventional FPAs su er the fundamental tradeo between the optical resolution and optical crosstalk. Metasurfaces, relying on the concept of abrupt phase shifts, can be used to build a new class of optical components. However, for realizing metasurfaces, optical resonators should cover a full 0-to-2 phase shift response with close to uniform amplitude response. In this thesis, to develop these metasurface optical components, nanoantennas that act as unit cell optical resonators were designed and modeled. A design methodology for building and optimizing these metasurfaces using the designed nanoantennas was developed. After obtaining the metasurfaces, we successfully addressed the problems of optical crosstalk in mid-wavelength infrared (MWIR) FPAs and weak eld localization in mirror contacts. Full-wave simulations con rmed major crosstalk suppression of the microlens arrays to achieve 1% optical crosstalk in the proposed metasurface FPAs, which outperforms all other types of MWIR FPAs reported to date. However, due to intrinsic absorption losses in metals, the resulting device e ciency was low ( 10%). To solve this problem, metallic nanoantennas were replaced by dielectric nanoantennas and the focusing e ciency was dramatically increased to 80%. This is the rst account of high-e ciency low-crosstalk metasurface MWIR FPAs. Full-wave simulations also con rmed the strong eld localization of metasurface mirrors that can impose a phase shift response close to 0 . The ndings of this thesis indicate that metasurface FPAs and mirrors are highly promising for future EO systems.