Integrating conventional optics into compact nanostructured surfaces is the goal of flat optics.Despite the enormous progress in this technology,there are still critical challenges for real-world applications due to t...Integrating conventional optics into compact nanostructured surfaces is the goal of flat optics.Despite the enormous progress in this technology,there are still critical challenges for real-world applications due to the limited operational efficiency in the visible region,on average lower than 60%,which originates from absorption losses in wavelengththick(~500 nm)structures.Another issue is the realization of on-demand optical components for controlling vectorial light at visible frequencies simultaneously in both reflection and transmission and with a predetermined wavefront shape.In this work,we developed an inverse design approach that allows the realization of highly efficient(up to 99%)ultrathin(down to 50 nm thick)optics for vectorial light control with broadband input-output responses in the visible and near-IR regions with a desired wavefront shape.The approach leverages suitably engineered semiconductor nanostructures,which behave as a neural network that can approximate a user-defined input-output function.Nearunity performance results from the ultrathin nature of these surfaces,which reduces absorption losses to nearnegligible values.Experimentally,we discuss polarizing beam splitters,comparing their performance with the best results obtained from both direct and inverse design techniques,and new flat-optics components represented by dichroic mirrors and the basic unit of a flat-optics display that creates full colours by using only two subpixels,overcoming the limitations of conventional LCD/OLED technologies that require three subpixels for each composite colour.Our devices can be manufactured with a complementary metal-oxide-semiconductor(CMOS)-compatible process,making them scalable for mass production at low cost.展开更多
Structural colors have drawn wide attention for their potential as a future printing technology for various applications,ranging from biomimetic tissues to adaptive camouflage materials.However,an efficient approach t...Structural colors have drawn wide attention for their potential as a future printing technology for various applications,ranging from biomimetic tissues to adaptive camouflage materials.However,an efficient approach to realize robust colors with a scalable fabrication technique is still lacking,hampering the realization of practical applications with this platform.Here,we develop a new approach based on large-scale network metamaterials that combine dealloyed subwavelength structures at the nanoscale with lossless,ultra-thin dielectric coatings.By using theory and experiments,we show how subwavelength dielectric coatings control a mechanism of resonant light coupling with epsilon-near-zero regions generated in the metallic network,generating the formation of saturated structural colors that cover a wide portion of the spectrum.Ellipsometry measurements support the efficient observation of these colors,even at angles of 70°.The network-like architecture of these nanomaterials allows for high mechanical resistance,which is quantified in a series of nano-scratch tests.With such remarkable properties,these metastructures represent a robust design technology for real-world,large-scale commercial applications.展开更多
基金This research received funding from KAUST(Award OSR-2016-CRG5-2995).Parallel simulations were performed on KAUST's Shaheen supercomputer.
文摘Integrating conventional optics into compact nanostructured surfaces is the goal of flat optics.Despite the enormous progress in this technology,there are still critical challenges for real-world applications due to the limited operational efficiency in the visible region,on average lower than 60%,which originates from absorption losses in wavelengththick(~500 nm)structures.Another issue is the realization of on-demand optical components for controlling vectorial light at visible frequencies simultaneously in both reflection and transmission and with a predetermined wavefront shape.In this work,we developed an inverse design approach that allows the realization of highly efficient(up to 99%)ultrathin(down to 50 nm thick)optics for vectorial light control with broadband input-output responses in the visible and near-IR regions with a desired wavefront shape.The approach leverages suitably engineered semiconductor nanostructures,which behave as a neural network that can approximate a user-defined input-output function.Nearunity performance results from the ultrathin nature of these surfaces,which reduces absorption losses to nearnegligible values.Experimentally,we discuss polarizing beam splitters,comparing their performance with the best results obtained from both direct and inverse design techniques,and new flat-optics components represented by dichroic mirrors and the basic unit of a flat-optics display that creates full colours by using only two subpixels,overcoming the limitations of conventional LCD/OLED technologies that require three subpixels for each composite colour.Our devices can be manufactured with a complementary metal-oxide-semiconductor(CMOS)-compatible process,making them scalable for mass production at low cost.
基金the Air Force Office of Scientific Research(MURI:FA9550-14-1-0389)for financial supportthe Center for Nanoscale Systems(CNS),a member of the National Nanotechnology Coordinated Infrastructure(NNCI)+3 种基金supported by the National Science Foundation under NSF award no.1541959.CNS is part of Harvard Universitysupport from KAUST(Award CRG-1-2012-FRA-005)the financial support of the‘Size matters’project(TDA Capital Ltd,London,UK)the financial support by the Master Thesis Grant of the Zeno Karl Schindler Foundation(Switzerland).
文摘Structural colors have drawn wide attention for their potential as a future printing technology for various applications,ranging from biomimetic tissues to adaptive camouflage materials.However,an efficient approach to realize robust colors with a scalable fabrication technique is still lacking,hampering the realization of practical applications with this platform.Here,we develop a new approach based on large-scale network metamaterials that combine dealloyed subwavelength structures at the nanoscale with lossless,ultra-thin dielectric coatings.By using theory and experiments,we show how subwavelength dielectric coatings control a mechanism of resonant light coupling with epsilon-near-zero regions generated in the metallic network,generating the formation of saturated structural colors that cover a wide portion of the spectrum.Ellipsometry measurements support the efficient observation of these colors,even at angles of 70°.The network-like architecture of these nanomaterials allows for high mechanical resistance,which is quantified in a series of nano-scratch tests.With such remarkable properties,these metastructures represent a robust design technology for real-world,large-scale commercial applications.
