Reflectorsareanessentialcomponentforon-chipintegratedphotonics.Here,weproposeanewmethodfordesigningreflectorsontheprevalentthin-film-on-insulatorplatformbyusinggenetic-algorithmoptimization.Insimulation,thedesignedreflectorwithafootprintofonly2.16μm×2.16μmcanachieve~97%reflectivityand1dBbandwidthaswideas220nm.Thestructureiscomposedofrandomlydistributedpixelsandishighlyrobustagainsttheinevitablecornerroundingeffectindevicefabrication.Inexperiment,wefabricatedon-chipFabry–Perot(FP)cavitiesconstructedfromoptimizedreflectors.ThoseFPcavitieshaveintrinsicqualityfactorsof>2000withthehighestvaluebeyond4000inaspectralwidthof200nm.ThereflectivityfittedfromtheFPcavityresonancesis>85%intheentirewavelengthrangeof1440–1640nmandisbeyond95%atsomewavelengths.ThefabricationprocessesareCMOScompatibleandrequireonlyonestepoflithographyandetch.Thedevicescanbeusedasastandardmoduleinintegratedphotoniccircuitryforwideapplicationsinon-chipsemiconductorlaserstructuresandopticalsignalprocessing.
