Silicon photonic Mach-Zehnder switches(MZSs)have been extensively investigated as a promising candidate for optical systems.However,conventional 2×2 MZSs are usually prone to the size variations of the arm waveguides due to imperfect fabrication,resulting in considerable random phase imbalance between the two arms,thereby imposing significant challenges for further developing next-generation N×N MZSs.Here we propose a novel design toward calibration-free 2×2 and N×N MZSs,employing optimally widened arm waveguides,enabled by novel compact tapered Euler S-bends with incorporated mode filters.With standard 180 nm CMOS foundry processes,more than thirty 2×2 MZSs and one 4×4 Benes MZS with the new design are fabricated and char-acterized.Compared with their conventional counterparts with 0.45-μm-wide arm waveguides,the present 2×2 MZSs exhibit significant reduction in the random phase imbalance.The measured extinction ratios of the present 2×2 and 4×4 MZSs operating in the all-cross state are 27-49 dB and～20 dB across the wavelength range of～60 nm,respectively,even without any calibrations.This work paves the way toward calibration-free large-scale N×N MZSs for next-generation silicon photonics.

State Key Laboratory for Modem Optical Instrumentation,College of Optical Science and Engineering,International Research Center for Advanced Photonics,Zhejiang University,Zijingang Campus,Hangzhou 310058,China;International Research Center for Advanced Photonics,Zhejiang University,Haining 314499,China

[1]LIJIA SONG;TANGNAN CHEN;WEIXI LIU;HONGXUAN LIU;YINGYING PENG;ZEJIE YU;HUAE LI;YAOCHENG SHI;DAOXIN DAI-.Toward calibration-free Mach-Zehnder switches for next-generation silicon photonics)[J].光子学研究（英文）,2022(03):793-801

MZSs,Benes,MZS

Toward,free,Mach,Zehnder,switches,next,generation,silicon,photonics,Silicon,have,been,extensively,investigated,promising,candidate,optical,systems,However,conventional,usually,prone,size,variations,waveguides,due,imperfect,fabrication,resulting,considerable,random,phase,imbalance,between,two,arms,thereby,imposing,significant,challenges,further,developing,Here,propose,novel,design,toward,employing,optimally,widened,enabled,compact,tapered,Euler,bends,incorporated,mode,filters,With,standard,CMOS,foundry,processes,more,than,thirty,new,fabricated,char,acterized,Compared,their,counterparts,present,exhibit,reduction,measured,extinction,ratios,operating,state,dB,across,wavelength,range,respectively,even,without,any,calibrations,This,work,paves,way,large,scale

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