1、September 20,2024A tutorial on metasurface designJonathan FanDepartment of Electrical EngineeringStanford UniversityJonathan Fan,Stanford UniversityOutlineConventional metasurface design with meta-atoms Optical resonators Propagation phase Geometric phaseFreeform metasurfaces design with the adjoint

2、 variables methodMachine learning-enhanced design Surrogate PDE solver accelerators Generative networks as global optimizers Large language modelsMetasurfaces as optical phase arraysConventional metasurfaces utilize arrays of subwavelength-scale“meta-atoms”that each support a unique phase response.P

3、hase response can be produced using several distinct mechanisms.Anomalous refractionScience,334,333(2011)Phase control with resonancesAn optical antenna is a driven harmonic oscillator,and it has up to a phase response around its resonance.ScatteringAbsorptionEAuhLSiLinear 1 m x 50 nm x 130 nm anten

4、na on Siq,m,x(t)Optics Express,19,22(2011)Achieving 2 phase shift with resonancesMetallic and dielectric nanostructure structures can achieve 2 phase shift using multiple resonances.Multi-resonant metallic antennasScience,334,333(2011);Opt&Phot News 1(2017)Multipolar resonances in dielectricsDyn

5、amical phase controlDielectric nanowaveguides can be used to transmit light with high transmission efficiency and tailored dynamical(i.e.,propagation)phase response.Design spaceConceptNano Lett.,15,6709(2015);Nat.Comm.,6,7069(2015)Geometric phase controlWith geometric phase,the meta-atoms are anisot

6、ropic nanoscale linearly birefringent half waveplates:A phase shift(i.e.,geometric phase)arises based on the relative angular orientation of the waveplate.PNAS,119,2122085119(2022);Adv.Opt.Phot.,13,836(2022)Meta-atom engineeringA wide range of meta-atom resonance,dispersion,and polarization engineer