High-Efficiency Broadband Mid-Infrared Flat Lens

Keywords

Abbe-Rayleigh diffraction limit; geometric tunability; localized surface plasmons; mid-infrared spectral domain; optical lens; polarization dependency

Abstract

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.

Publication Date

7-4-2018

Publication Title

Advanced Optical Materials

Volume

6

Issue

13

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1002/adom.201800216

Socpus ID

85049522213 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85049522213

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