Achromatic super-oscillatory lenses with subwavelength focusing

摘要

Lenses are crucial to light-enabled technologies.Conventional lenses have been perfected to achieve near-diffraction-limited resolution and minimal chromatic aberrations.However,such lenses are bulky and cannot focus light into a hotspot smaller than a half-wavelength of light.Pupil filters,initially suggested by Toraldo di Francia,can overcome the resolution constraints of conventional lenses but are not intrinsically chromatically corrected.Here we report single-element planar lenses that not only deliver sub-wavelength focusing,thus beating the diffraction limit of conventional refractive lenses,but also focus light of different colors into the same hotspot.Using the principle of super-oscillations,we designed and fabricated a range of binary dielectric and metallic lenses for visible and infrared parts of the spectrum that are manufactured on silicon wafers,silica substrates and optical fiber tips.Such low-cost,compact lenses could be useful in mobile devices,data storage,surveillance,robotics,space applications,imaging,manufacturing with light and spatially resolved nonlinear microscopies.