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| 1 | Design and analysis of extended depth of focus metalenses for achromatic computational imaging显示文摘Metasurface optics have demonstrated vast potential for implementing traditional optical components in an ultracompact and lightweight form factor.Metasurfaces,however,suffer from severe chromatic aberrations,posing serious limitations on their practical use.Eixisting approaches for circumventing this involving dispersion engineering are limited to small apertures and often entail multiple scatterers per unit cell with small feature sizes.Here,we prescnt an alternative technique to mitigatc chromatic aberration and demonstrate high-quality,full-color imaging using extended depth of focus(EDOF)metalenses and computational reconstruction.Previous EDOF metalenses have relied on cubic phase masks,where the image quality suffers from asymmetric artefacts.Here we demonstrate the use of rotationally symmetric masks,including logarithmic-aspherical,and shifted axicon masks,to mitigate this problem.Our work will inspire further development in achromatic metalenses beyond dispersion engineering and hybrid optical-digital metasurface systems. | LUOCHENG HUANA JAMES WHITEHEAD SHANE COLBURN ARKA MAJUMDAR | 2020 | Photonics Research2020，8，10： | 5 |
| 2 | MEMS-actuated metasurface Alvarez lens显示文摘Miniature lenses with a tunable focus are essential components for many modern applications involving compact optical systems.While several tunable lenses have been reported with various tuning mechanisms,they often face challenges with respect to power consumption,tuning speed,fabrication cost,or production scalability.In this work,we have adapted the mechanism of an Alvarez lens–a varifocal composite lens in which lateral shifts of two optical elements with cubic phase surfaces give rise to a change in the optical power–to construct a miniature,microelectromechanical system(MEMS)-actuated metasurface Alvarez lens.Implementation based on an electrostatic MEMS generates fast and controllable actuation with low power consumption.The utilization of metasurfaces–ultrathin and subwavelength-patterned diffractive optics–as optical elements greatly reduces the device volume compared to systems using conventional freeform lenses.The entire MEMS Alvarez metalens is fully compatible with modern semiconductor fabrication technologies,granting it the potential to be mass-produced at a low unit cost.In the reported prototype operating at 1550 nm wavelength,a total uniaxial displacement of 6.3µm was achieved in the Alvarez metalens with a direct-current(DC)voltage application up to 20V,which modulated the focal position within a total tuning range of 68µm,producing more than an order of magnitude change in the focal length and a 1460-diopter change in the optical power.The MEMS Alvarez metalens has a robust design that can potentially generate a much larger tuning range without substantially increasing the device volume or energy consumption,making it desirable for a wide range of imaging and display applications. | Zheyi Han Shane Colburn Arka Majumdar Karl F.Bohringer | 2020 | Microsystems & Nanoengineering2020，6，1： | 1 |
| 3 | Fast extended depth of focus meta-optics for varifocal functionality显示文摘Extended depth of focus(EDOF)optics can enable lower complexity optical imaging systems when compared to active focusing solutions.With existing EDOF optics,however,it is difficult to achieve high resolution and high collection efficiency simultaneously.The subwavelength spacing of scatterers in a meta-optic enables the engineering of very steep phase gradients;thus,meta-optics can achieve both a large physical aperture and a high numerical aperture.Here,we demonstrate a fast(f/1.75)EDOF meta-optic operating at visible wavelengths,with an aperture of 2 mm and focal range from 3.5 mm to 14.5 mm(286 diopters to 69 diopters),which is a 250×elongation of the depth of focus relative to a standard lens.Depth-independent performance is shown by imaging at a range of finite conjugates,with a minimum spatial resolution of∼9.84μm(50.8 cycles/mm).We also demonstrate operation of a directly integrated EDOF meta-optic camera module to evaluate imaging at multiple object distances,a functionality which would otherwise require a varifocal lens. | James E.M.Whitehead Alan Zhan Shane Colburn Luocheng Huang Arka Majumdar | 2022 | Photonics Research2022，10，3： | 0 |
| 4 | Polarization-controlled optical holography using flat optics显示文摘Due to the large number of degrees of freedom offered by nanoscale scatterers,a single flat optic can project different images at different distances depending on the polarization of the light,opening up opportunities for optical encryption and augmented reality systems. | Arka Majumdar Shane Colburn | 2020 | Light(Science & Applications)2020，9，1： | 0 |
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