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(a) Calculated geometry of carbon nanotube based cylindrical Fresnel lens having a design focal length of 125 μm at λ = 800 nm. The lens measured 77 μm by 2 mm. (b) Schematic showing the geometry and reflection mode operation of the Fresnel lens, incident light form the top.
2D cross-sectional geometry of the simulated CNT based Fresnel lens on silicon. Opaque zones are represented by the CNT arrays and the lens operated in reflection mode. Insets show the CNT arrays and mesh elements utilized to resolve the computational domain.
Simulated wave propagation (intensity) of (a) 850 nm and (b) 1550 nm waves across the Fresnel lens. The reflected light is focused into the focus plane. (c) Intensity plots with distance extending from the lens center to the focal plane. The focal lengths decrease with increasing λ.
(a) SEM image of cylindrical Fresnel lens based on the carbon nanotube forests, fabricated on a silicon substrate. (b) Higher magnification image showing the CNT forest in an opaque Fresnel zone.
(a) CNT based cylindrical Fresnel lenses under an optical microscope. Each lens having 15 opaque zones extended to an area of width 77 μm and length 2 mm. (b) Fresnel lenses showing the focusing of light in the focal plane. (c) 2D intensity plot across the focal plane. Focused rows of light are observed in the middle of the lenses. (d) Light intensity plot across the Fresnel lens showing focusing.
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