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 s...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.展开更多
As artificial neural networks(ANNs)continue to make strides in wide-ranging and diverse fields of technology,the search for more efficient hardware implementations beyond conventional electronics is gaining traction.I...As artificial neural networks(ANNs)continue to make strides in wide-ranging and diverse fields of technology,the search for more efficient hardware implementations beyond conventional electronics is gaining traction.In particular,optical implementations potentially offer extraordinary gains in terms of speed and reduced energy consumption due to the intrinsic parallelism of free-space optics.At the same time,a physical nonlinearity—a crucial ingredient of an ANN—is not easy to realize in free-space optics,which restricts the potential of this platform.This problem is further exacerbated by the need to also perform the nonlinear activation in parallel for each data point to preserve the benefit of linear free-space optics.Here,we present a free-space optical ANN with diffraction-based linear weight summation and nonlinear activation enabled by the saturable absorption of thermal atoms.We demonstrate,via both simulation and experiment,image classification of handwritten digits using only a single layer and observed 6% improvement in classification accuracy due to the optical nonlinearity compared to a linear model.Our platform preserves the massive parallelism of free-space optics even with physical nonlinearity,and thus opens the way for novel designs and wider deployment of optical ANNs.展开更多
基金UW Reality LabGoogle+5 种基金FaccbookFutureweiAmazonSamsung Advanced Institute of TechnologyNationalScience Foundation(NSF-1825308)Part of this work was conducted at the Washington Nanofabrication Facility/Molecular Analysis Facility,a National Nanotechnology Coordinated Infrastructure(NNCI)sitc ar thc University of Washington,which is supported in part by funds from the National Sceience Foundation(NNCI-1542101,1337840,and 0335765),the Narional Institures of Health,the Molecular Engineering&Sciences Institute,the Clean Energy Institute,the Washington Research Foundation,the M.J.Murdock Charitable Trust,Altarech,Class One Technology,GCE Market,Google,and SPTS.
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.
文摘As artificial neural networks(ANNs)continue to make strides in wide-ranging and diverse fields of technology,the search for more efficient hardware implementations beyond conventional electronics is gaining traction.In particular,optical implementations potentially offer extraordinary gains in terms of speed and reduced energy consumption due to the intrinsic parallelism of free-space optics.At the same time,a physical nonlinearity—a crucial ingredient of an ANN—is not easy to realize in free-space optics,which restricts the potential of this platform.This problem is further exacerbated by the need to also perform the nonlinear activation in parallel for each data point to preserve the benefit of linear free-space optics.Here,we present a free-space optical ANN with diffraction-based linear weight summation and nonlinear activation enabled by the saturable absorption of thermal atoms.We demonstrate,via both simulation and experiment,image classification of handwritten digits using only a single layer and observed 6% improvement in classification accuracy due to the optical nonlinearity compared to a linear model.Our platform preserves the massive parallelism of free-space optics even with physical nonlinearity,and thus opens the way for novel designs and wider deployment of optical ANNs.
