Cylindrical Fresnel lenses based on carbon nanotube forests

Abstract

The forests of carbon nanotubes have been termed as the darkest man-made materials. Such materials exhibit near-perfect optical absorption (reflectance ∼ 0.045%) due to low reflectance and nanoscale surface roughness. We have demonstrated the utilization of these perfectly absorbing forests to produce binary amplitude cylindrical Fresnel lenses. The opaque Fresnel zones are defined by the dark nanotube forests and these lenses display efficient focusing performance at optical wavelengths. Lensing performance was analyzed both computationally and experimentally with good agreement. Such nanostructure based lenses have many potential applications in devices like photovoltaic solar cells.

Graphene nanoribbon based plasmonic Fresnel zone plate lenses

“…As compared with traditional lenses, FZP lenses are at, have lower weight and volume, higher numerical aperture, and are widely used in silicon-based electronics. 34,35 The proposed graphene-based plasmonic FZP lens is analogous to conventional FZP lens, but with each dark Fresnel zone being composed of an array of ne graphene NRs, which resonant at specic wavelengths. 36 Graphene is almost transparent with negligible reection in the visible regime.…”

Carbon Nanotube Array Based Binary Gabor Zone Plate Lenses

“…A binary Gabor zone plate consists of transparent and opaque zones with respect to the incident irradiation which allows it to act as a lens. As for reflective binary zone plate, the reflections from the opaque zones will decrease the focusing efficiency 11 – 13 . Due to the high absorption of CNT array in both UV 14 , 15 and visible regimes 16 (reflectance can be up to 0.045% in visible regime), it will be a perfect material for the opaque areas in a Gabor zone plate.…”

Fresnel lens based on silicon nanowires

“…Most of the available Fresnel lenses are the transmission type. Recently, a reflective Fresnel lens based on carbon nanotube forests was proposed, showing high contrast focusing of light owing to the near-perfect optical absorption of carbon nanotubes [6][7][8][9].…”