KISS超表面研讨会：超表面简介

Noah A. Rubin --University of California San DiegoKISS Metasurfaces WorkshopPasadena, CA, USA – September 23-28, 2024 Presentation Outline 1.What are metasurfaces? Broad overview.2.Historical context.3.Methods of imparting phase in diffractive optics.4.Metasurface polarization optics.5.Potential applications astronomy (incl. high-contrast imaging). What is a “metasurface”? C. Pfeiffer and A. Grbic,Phys. Rev. Lett..110(197401),2013Microwaves M. Khorasaninejad et al.,Science352(6290), 2016 N. Yu et al.,Science334(6054), 2011λ = 8 μm Cu on RO4003 One definition: Asubwavelength-spaced array of phase-shifting elements intended to enact somedesired behavior (either in reflection or transmission), generally in free-space. These elements – the“meta-atoms” – can be designed at-will and fabricated with standard semiconductor fabricationtechniques. Metasurface application areas A. Arbabi et al.,Nat. Comm.(2016) R.C. Devlin et al.,Science358(2017) MiniatureCameras Polarizationoptics/polarimetry Vortex phaseplates Spectroscopy This list is not exhaustive and this talk will be necessarilyincomplete. In some ways, any topic involving free space propagation canrelate to metasurfaces, making this an impossibly broad field Metasurfaces – the hype • Metasurfaces are often billed as “2D metamaterials”, fabricated on aNvidia Developer TechnicalBlog KISS Metasurfaces Workshop – September 23, 2024plane. Sometimes also calledflat optics.• The scientific literature and even the popular press abound with claimssurrounding metasurfaces’ ability to remake free-space optical systemscompletely. Focus of this talk • The field of metasurfaces is reaching a point of maturity wherewe have to soberly consider where these may – and may not –hold relevance for real optical systems. • All metasurface applications involve tradeoffs, sometimessignificant. • In this talk, I will (imperfectly) review what I find to be theessential physical principles – at a very high level. • Only passive metasurfaces will be considered. Historical context Wherefore cometh thou, metasurface? The first metasurface “…I made aſquare of parallel hairsabout half an inch each way…I got awatchmaker to cut a very fineſcrew ontwo pieces ofſmall braſwire. In thethreads of theſeſcrews, 106 of whichmade one inch, the hairs were laid 50or 60 in number.” F. Hopkinson and D. Rittenhouse, "An optical problem,proposedby Mr.Hopkinson,and solved by Mr.Rittenhouse".TransactionsoftheAmericanPhilosophical Society.2: 201–6,1786. The first metasurface “Holding the hairs parallel to theſlit,and looking towards theſky, I sawthree parallel lines, almost equal inbrightness…I took out the hairs andput in others…of theſe 190 made oneinch…the three middle lines of lightwere now notſo bright as they hadbeen before…” F. Hopkinson and D. Rittenhouse, "An optical problem,proposedby Mr.Hopkinson,and solved by Mr.Rittenhouse".TransactionsoftheAmericanPhilosophical Society.2: 201–6,1786. The first metalenses Both owed to Fresnel in the years ~1810-20 KISS Metasurfaces Workshop – September 23, 2024 Anticipations in RF/microwaves Reflectarrays– (example here from NASAJPL’s MarCO cubesat, f ~ 420 MHz) Many metasurface concepts have longhistories at RF, where features can bemacroscopic in size. Radar phased array(f ~ 420 MHz, part of theUS Cold War-era missile early warning system) Holography Dennis Gabor – 1971 Nobel Prizein Physics for Optical Holography Recording and reconstructing the interference ofwaves. Computer-generated holography“Usually a hologram is produced bymeans of an interference experiment. Here,however,weletacomputer-guidedplotter draw thehologram…” “Metasurfaces” are computer generatedholograms “The production of the filter or hologram wasdonefirstatlargescale,andthenphotographicallyreduced…in one case thedrawing was made by hand; in another caseby a computer-guided plotter.” BR Brown and AW Lohmann,Appl. Opt.5(6),1966BR Brown and AW Lohmann,IBM J. Res. Develop.13(2), 1969 Needless to say, we have gottenmuchbetter atprinting What has been possible with electronbeam lithography has always been farahead The inexorable march of Moore’s Law Diffractive optical elements Marketing material for Digital Optics Corporation (c.1995)So why are metasurfaces“Wedesign and produce lenses with unique opticalproperties by creating microscopic patterns in substratesincluding glass, silicon, and plastic. Diffractives are notonly lighter, smaller, and lower in cost than conventionalrefractive lenses, but can also perform functions that areimpossible using conventional refractives.” regarded as a new/emergingfield in 2024? “Metamaterials” RA Shelby, DR Smith, and S Shultz,Science292(5514),2001 Negative refractive index The field of metamaterials sought to explore new devices and physics bycontrolling the constitutive parameters (ε, μ) of artificial electromagneticmedia. KISS Metasurfaces Workshop – September 23, 2024 The genesis of metasurfaces(fro