High‐Efficiency Broadband Mid‐Infrared Flat Lens. Issue 13 (19th April 2018)

• Record Type: Journal Article
• Authors: Safaei, Alireza; Vázquez‐Guardado, Abraham; Franklin, Daniel; Leuenberger, Michael N.; Chanda, Debashis
• Is Part Of: Advanced optical materials. Volume 6:Issue 13(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-04-19
• Subjects: Abbe‐Rayleigh diffraction limit -- geometric tunability -- localized surface plasmons -- mid‐infrared spectral domain -- optical lens -- polarization dependency; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.201800216
• Languages: English
• ISSNs: 2195-1071

Abstract

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. Abstract : High efficiency broadband flat optical lens based on plasmonic nanoantenna is designed in mid‐infrared range. For the optimum design, the measured transmission reaches >60% over the entire 4–10 μm mid‐infrared spectral range with low FWHM/wavelength. Such flat lens overcomes the challenges associated with the unavailability of mid‐infrared transparent materials for low footprint planar integration with thermal imaging systems.