NANO.ETTERSubscriber access provided by-Access paid by the UCSB LibrariesCommunicationAn Ultra-high Numerical Aperture Metalens at Visible WavelengthsHaowen Liang,Qiaoling Lin,Xiangsheng Xie,Qian Sun,Yin Wang,LidanZhou,Lin Liu,Xiangyang Yu,Jianying Zhou,Thomas F.Krauss,and Juntao LiNano Lett.,Just Accepted Manuscript.DOI:10.1021/acs.nanolett.8b01570.Publication Date (Web):25 Jun 2018Downloaded from http://pubs.acs.org on June 25,2018Just Accepted"Just Accepted"manuscripts have been peer-reviewed and accepted for publication.They are postedonline prior to technical editing,fommatting for publication and author proofing.The American ChemicalSociety provides"Just Accepted"as a service to the research community to expedite the disseminationof scientific material as soon as possible after acceptance."Just Accepted"manuscripts appear infull in PDF format accompanied by an HTML abstract."Just Accepted"manuscripts have been fullypeer reviewed,but should not be considered the official version of record.They are citable by theDigital Object Identifier(DOI)."Just Accepted"is an optional service offered to authors.Therefore,the "Just Accepted"Web site may not include all articles that will be published in the journal.Aftera manuscript is technically edited and fommatted,it will be removed from the "Just Accepted"Website and published as an ASAP article.Note that technical editing may introduce minor changesto the manuscript text and/or graphics which could affect content,and all legal disclaimers andethical guidelines that apply to the journal pertain.ACS cannot be held responsible for errors orconsequences arising from the use of information contained in these "Just Accepted"manuscripts.ACS Publicationsis published by the American Chemical Society.1155 Sixteenth Street N.W.,Washington,DC 20036Published by American Chemical Society.Copyright American Chemical SocietyHowever,no copyright claim is made to original U.S.Government works,or worksPage 1 of21Nano Letters12345678An Ultra-high Numerical Aperture Metalens at9111Visible Wavelengths1134151Haowen Liang',Qiaoling Lin Xiangsheng Xie Qian Sun'Yin Wang',Lidan Zhou',Lin1189Liu',Xiangyang Yu',Jianying Zhou',Thomas F Krauss and Juntao Li*2State Key Laboratory of Optoelectronic Materials and Technologies,School of Physics,School24of Electronics and Information Technology,Sun Yat-Sen University,Guangzhou 510275,China2Department of Physics,College ofScience,Shantou University,Shantou 515063,China29SDepartment of Physics,University of York,York YO10 5DD,UKCorrespondent author:lijt3@mail.sysu.edu.cn5KEYWORDS:dielectric metalens,crystalline silicon,high numerical aperture,oil immersion90ACS Paragon Plus EnvironmentNano LettersPage 2 of 211234567ABSTRACT:Subwavelength imaging requires the use of high numerical aperture (NA)lensestogether with immersion liquids in order to achieve the highest possible resolution.Followingexciting recent developments in metasurfaces that have achieved efficient focusing and novel910beam-shaping,the race is on to demonstrate ultra-high NA metalenses.The highest NA that has111213been demonstrated so far is NA=1.1,achieved with a TiO2 metalens and back-immersion.Here,41we introduce and demonstrate a metalens with high NA and high transmission in the visible161range,based on crystalline silicon(c-Si).The higher refractive index of silicon compared to TiO2189allows us to push the NA further.The design uses the geometric phase approach also known as22the Pancharatnam-Berry (P-B)phase and we determine the arrangement of nano-bricks using a24hybrid optimization algorithm (HOA).We demonstrate a metalens with NA =0.98 in air,a27bandwidth(FWHM)of 274 nm and a focusing efficiency of 67%at 532 nm wavelength,which29is close to the transmission performance of a TiO2 metalens.Moreover,and uniquely so,our33metalens can be front-immersed into immersion oil and achieve an ultra-high NA of 1.48experimentally and 1.73 theoretically,thereby demonstrating the highest NA of any metalens in33the visible regime reported to the best of our knowledge.The fabricating process is fully3compatible with CMOS technology and therefore scalable.We envision the front-immersion39design to be beneficial for achieving ultra-high NA metalenses as well as immersion metalens4doublets,thereby pushing metasurfaces into practical applications such as high resolution,low-cost confocal microscopy and achromatic lenses.4649ACS Paragon Plus Environment2