Abstract
Plasmonic metalenses are optical elements that are able to shape the amplitude and the phase of light with a high spatial resolution, standing as promising elements for new low-weight imaging technologies. A desired characteristic for metalenses is to have an extended depth of focus (DOF) to bring a larger tolerance of placement of the image plane, reducing image blurring and increasing light directivity. Based on the Fresnel biprism and using the integral equation method, we numerically demonstrate light focusing with cylindrical plasmonic metalenses that are able to generate large DOF values of up to 150λ with transmission efficiencies around 50%. The easiness in the design of our plasmonic metalenses represents an advantage in terms of fabrication, opening new possibilities for the development of small-size lenses for light focusing and imaging applications.
Highlights
Since the demonstration of extraordinary optical transmission through thin metallic films structured with subwavelength hole arrays,1 new horizons have been opened in the design and fabrication of flat metasurfaces to control light transmission close to the diffraction limit, a situation hardly achievable with bulk-optical systems.2,3 With these plasmonic metasurfaces, it is possible to control amplitude, phase,4,5 polarization, and even orbital angular momentum6,7 to achieve structured light beams.8–10Among the large variety of metasurfaces can be found plasmonic metalenses (PMs), devices that allow light focusing in reduced spatial regions
Based on the Fresnel biprism and using the integral equation method, we numerically demonstrate light focusing with cylindrical plasmonic metalenses that are able to generate large depth of focus (DOF) values of up to 150λ with transmission efficiencies around 50%
Based on the integral equation method,26–29 in this contribution, we present the design of large DOF plasmonic metalenses consisting of arrays of nanoslits in a thin metallic layer
Summary
Since the demonstration of extraordinary optical transmission through thin metallic films structured with subwavelength hole arrays, new horizons have been opened in the design and fabrication of flat metasurfaces to control light transmission close to the diffraction limit, a situation hardly achievable with bulk-optical systems. With these plasmonic metasurfaces, it is possible to control amplitude, phase, polarization, and even orbital angular momentum to achieve structured light beams.. Among the large variety of metasurfaces can be found plasmonic metalenses (PMs), devices that allow light focusing in reduced spatial regions Their operation principle is based on the constructive interference of light scattered by each one of the subwavelength structures (scatterers) placed in the surface of a thin metallic layer.. Less complex arrays of scatterers have been proposed for the design of PMs, like multilayered arrays of concentric rings, but only short DOF values have been achieved (3.6λ).22 Another option for light focusing is by employing nanoslits practiced in thin metallic layers..
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