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High‐Efficiency Broadband Mid‐Infrared Flat Lens
Author(s) -
Safaei Alireza,
VázquezGuardado Abraham,
Franklin Daniel,
Leuenberger Michael N.,
Chanda Debashis
Publication year - 2018
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201800216
Subject(s) - materials science , optics , optoelectronics , dielectric , infrared , lens (geology) , plasmon , planar , physics , computer science , computer graphics (images)
Integrated photonic circuits and infrared imaging systems demand compact optical components. Dielectric diffractive optics enables miniaturization of the curved refractive optics into planar structure by encoding phase over a 2D plane. However, in the mid‐infrared wavelength range, such engineered dielectric surfaces are not efficient, because optically transparent dielectric scatterers with high index contrast in the mid‐infrared spectral range suffer from low bandwidth and high thermal noise in long wavelengths. Here, a planar optical lens based on ultrathin gold plasmonic nanostructure operating in the mid‐infrared spectral range is demonstrated. The design enables subwavelength focusing beyond the Abbe‐Rayleigh diffraction limit while maintaining high transmission efficiency (≈60%) with excellent agreement between electromagnetic simulations and confocal measurements. Single and bilayer flat lenses designed for subwavelength polarization‐dependent line and polarization‐independent point focusing, respectively, are demonstrated. Such geometry‐defined tunable optical response overcomes the challenges associated with the unavailability of mid‐infrared transparent materials for low footprint planar integration with thermal imaging systems.