micromches Article Rottg Circulr Micro-Pltform with Integrted Wveguides Ltchg Arm for Reconfigurble Integrted Optics Jonthn Briere 1,2, *, Mohnnd Y. Elsyed 3, Menouer Sidni 3, Mrt Bérrd 1, Philippe-Olivier Beulieu 2, Hdi Rbbni-Hghighi 2, Frederic Nbki 3 Michël Ménrd 2 1 Aeponyx Inc., Montrel, QC H3C 4J9, Cnd; mberrd@eponyx.com 2 Deprtment Computer Science, Université du Québec à Montrél, Montrel, QC H2X 3Y7, Cnd; beulieu.philippe-olivier@courrier.uqm.c (P.-O.B.); hdi.rbbni@gmil.com (H.R.-H.); menrd.michel@uqm.c (M.M.) 3 Deprtment Electricl Engeerg, École de Technologie Supérieure, Montrel, QC H3C 1K3, Cnd; mohnnd.elsyed@mil.mcgill.c (M.Y.E.); menouer.sidni@gmil.com (M.S.); frederic.nbki@etsmtl.c (F.N.) * Correspondence: jbriere@eponyx.com; Tel.: +1-514-360-7746 (ext. 6006) Received: 31 October 2017; Accepted: 30 November 2017; Publhed: 1 December 2017 Abstrct: Th work presents lterlly rottg micromched pltform tegrted under opticl wveguides to control -plne propgtion direction light with die to select one multiple outputs. pltform designed to exhibit low constnt opticl losses throughout motion rnge ctuted electrostticlly usg n optimized circulr comb drive. An ngulr motion ±9.5 usg 180 V demonstrted. To mimize opticl losses between movg fixed prts, gp-closg mechnm implemented to reduce itil ir gp to submicron vlues. A ltch structure implemented to hold pltform plce with resolution 0.25 over entire motion rnge. pltform ws tegrted with silicon nitride wveguides to crete crossbr switch prelimry opticl mesurements re reported. In br stte, loss ws mesured to be 14.8 db with gp closed wheres cross stte it ws 12.2 db. To uthors knowledge, th first opticl switch bsed on rottg microelectromechnicl device with tegrted silicon nitride wveguides reported to dte. Keywords: microelectromechnicl systems (MEMS); electrosttic ctutor; ltch; micro-optoelectro-mechnicl systems (MOEMS); micro-pltform; opticl switch; scnng; tegrted optics; silicon-on-sultor (SOI) MEMS; opticl wveguide 1. Introduction Photonic tegrted circuits re receivg cresg ttention s promg technology for next genertions high-speed, low-loss, low-power consumption, low-cost communiction sensg systems. Concurrently, progress microelectromechnicl systems (MEMS) hs helped mituriztion reliztion complex opticl components on-chip such s lenses, mirrors, filters, bem splitters, grtgs [1]. se elements re commonly referred to s micro-opto-electro-mechnicl systems (MOEMS) [1]. emergence silicon-on-sultor (SOI) wfer btch processg technology hs ccelerted development high performnce relible pssive components cludg low-loss wveguides, power splitters multiplexers [2,3]. Dem for high-speed opticl communictions pushed development severl novel opticl systems, e.g., micromirror rrys for lrge opticl spce switches [4], contully tunble opticl dely les [5], reconfigurble opticl dd/drop multiplexers (ROADMs) [6]. MEMS mirrors re promg cidtes Micromches 2017, 8, 354; doi:10.3390/mi8120354 www.mdpi.com/journl/micromches
Micromches 2017, 8, 354 2 19 for pplictions where size, weight, power consumption, cost re criticl prmeters [7 15]. y hve been used severl pplictions to vribly deflect n opticl bem, e.g., wve front control [8], scnners [9,10] vriety smll lrge-scle opticl switches [10 13]. MEMS ctutors re receivg cresg ttention for co-tegrtion with opticl components ledg to severl novtive photonic devices [16,17]. y cn be used for out--plne ctution s [18], or -plne ctution s [19 29]. Rotry comb ctutors re one key ctutor type. In [19 22], -plne rotry comb-drives suspended by serpente flexures were demonstrted to chieve lrger rottion ngles thn those suspended by clmped stright bems. serpente flexures enbled -plne rotry comb-drives to mechniclly rotte over 9 ech ngulr direction t drivg voltge bis less thn 60 V. However, devices exhibit reltively low resonnce frequencies ~410 Hz, which limits speed opertion. In [23], design rel pivot formed by double-clmped bem for rottionl tung structures MEMS tunble lsers ws presented. structure chieved rottion ~4.7 with 75 V ctution voltge. In [24], rotry comb-drives with deflection ngle up to 2.8 were demonstrted. In [25], rotry comb-drive electrosttic ctutors with virtul pivotl pot rottion were designed fbricted for pplictions externl cvity tunble lsers Littmn configurtion. A mximum rottion ±1.5 t 190 V ws chieved. In [26], long-rm comb-drive rotry ctutor with n externlly mounted lrge mirror presented. Sttic chrcteriztion mesurements show tht ctutor cn chieve rottionl ngle 3 with n pplied voltge 130 V. In [27], MEMS switch bsed on rotry electrosttic comb ctutor ws presented. switch uses 50 V DC ctution voltge exhibits 0.774 rottion ngle. In [28], rotry comb-ctutors re used to relize micro-gripper. It chieves ~2 ngulr dplcement with 100 V ctution voltge. Accordgly, th work presents development n novtive lterlly movg rottionl micro-pltform tht provides significnt lterl deflection ngle usg compct footprt. micro-pltform tegrted under opticl wveguides to control direction propgtion light with die. Prior work on MEMS ctutor ws briefly presented [29]. Th rticle presents detiled nlys optimiztion s well s testg results fbricted structures. To troduce different spects relted to micro-pltform, envioned system micro-pltform re dcussed Section 2. n, micro-pltform designs re described Section 3. test setup presented Section 4. experimentl results different implemented devices s well s limittions ech device re n reported Section 5. Th section lso cludes opticl testg results crossbr opticl switch implemented usg pltform. Flly, results re dcussed Section 6 long with conclusion. 2. System Overview 2.1. Trgeted Micro-Opto-Electro-Mechnicl System micro-pltform presented here ws designed to be tegrted with opticl wveguides on sme chip usg novel fbriction technology [26,30]. Such tegrtion chllengg becuse MEMS devices corporte suspended movble prts, which mens tht light propgtg side wveguide might fce dcontuities resultg significnt opticl losses. Creful engeerg required th cse order to mimize losses t se terfces optimize propgtion light. By tkg dvntge silicon nitride (Si 3 N 4 ) core enclosed silicon oxide (SiO 2 ) clddg, pltform llows to crete sgle mode low propgtion loss wveguides over strd silicon-on-sultor (SOI) substrtes. Silicon nitride n excellent choice to operte telecom b round 1550 nm. Th becuse it cn be nneled to drive out hydrogen order not to suffer N-H Si-H bonds bsorption t round 1520 nm [31,32]. Silicon nitride cn lso be used with dtcom rnge down to 500 nm where silicon suffers bsorption below 1100 nm. Furrmore, th wveguide structure cn esily be tilored to different pplictions by djustg thickness different lyers, such s polriztion sensitive filters [33,34], vrious deposition methods vilble
Micromches 2017, 8, 354 3 19 for se mterils provide flexibility defition fbriction process. 1 shows schemtics two exmple pplictions micro-pltform s 1 N switch crossbr switch cell s well s cross section illustrtg mteril stck. Micromches 2017, 8, 354 3 18 () (c) 1. 1. Exmple pplictions proposed ctutor: () schemtic crossbr switch; schemtic 11 N mirror-bsed switch; (c) cross-section key mteril stck. In 1 switch, micro-pltform lies under plnr opticl wveguide, s shown In 1 N switch, micro-pltform lies under plnr opticl wveguide, s shown 1b, implements rottionl solid-immersion MEMS mirror [35], where light propgtes 1b, implements rottionl solid-immersion MEMS mirror [35], where light propgtes nitride core lyer. put wveguide brgs light signl to movble MEMS mirror nitride core lyer. put wveguide brgs light signl to movble MEMS mirror structure by crossg ir gp between wveguides plnr wveguide. light bem structure by crossg ir gp between wveguides plnr wveguide. light bem strts to diverge side plnr wveguide until it reches curved bck fcet mirror tht strts to diverge side plnr wveguide until it reches curved bck fcet mirror tht reflects light towrd to output wveguide while refocusg it. reflects light towrd to output wveguide while refocusg it. mirror cn reflect light through totl ternl reflection usg effective dex mirror cn reflect light through totl ternl reflection usg effective dex contrst contrst between ir behd mirror silicon nitride plnr wveguide or usg between ir behd mirror silicon nitride plnr wveguide or usg reflective cotg reflective cotg on bck fcet plnr wveguide. bility to rotte mirror llows on bck fcet plnr wveguide. bility to rotte mirror llows for positiong for positiong output focl pot light, consequently, selectg output wveguide. output focl pot light, consequently, selectg output wveguide. light bem light bem crosses ir gp between movble mirror prt nchored wveguide crosses ir gp between movble mirror prt nchored wveguide once more on once more on output side. output side. For crossbr switch cell [36], micro-pltform crries Si3N4 wveguides cldded with 4 For crossbr switch cell [36], micro-pltform crries Si 3 N 4 wveguides cldded with 4 µm µm SiO2 lyers. Inverted tpers re locted t edges chip to improve couplg with lensed SiO 2 lyers. Inverted tpers re locted t edges chip to improve couplg with lensed fibers by engeerg opticl mode on ech side gp defg rottionl pltform fibers by engeerg opticl mode on ech side gp defg rottionl pltform to mimize diffrction crese lignment tolernce, thus improvg on opticl losses through to mimize diffrction crese lignment tolernce, thus improvg on opticl losses through gp. clddg widened se regions to ensure tht exped opticl mode does not terct with clddg boundries. put wveguide brgs light signl to movble MEMS structure by crossg ir gp between wveguides. switch hs three put output wveguides. middle wveguide serves for lignment purposes durg testg would not be required switch fbric. In br stte, when pltform not rotted only gp-closg ctutor ctivted, signl from put wveguides 1 2 re trnsferred to
Micromches 2017, 8, 354 4 19 gp. clddg widened se regions to ensure tht exped opticl mode does not terct with clddg boundries. put wveguide brgs light signl to movble MEMS structure by crossg ir gp between wveguides. switch hs three put output wveguides. middle wveguide serves for lignment purposes durg testg would not be required switch fbric. In br stte, when pltform not rotted only gp-closg ctutor ctivted, signl from put wveguides 1 2 re trnsferred to mtchg outputs. To put switch cross stte, pltform rotted by 5 counter clockwe. n, put 2 connected to output 1 by wveguide middle pltform when gp closed. or wveguides rem unconnected. Neverless, se two sttes re sufficient to build crossbr mtrix by fbrictg n rry th device. light bem crosses ir gp between movble mirror prt nchored wveguide once more on output side. An electrostticlly ctuted gp-closg mechnm tht trnsltes MEMS micro-pltform utilized order to reduce size ir gp fter rottion consequently limit opticl losses due to expnsion light bem ir gp, which desirble for both proposed pplictions. Si 3 N 4 core thickness wveguide dimensions re optimized for requirements ech prticulr ppliction. 2.2. Micro-Pltform Sce opticl properties mteril depend on its temperture, power efficient MEMS ctution mechnm essentil order to mt temperture opticl components constnt, precludg use rml ctution. Mgnetic electrosttic ctution mechnms were considered for device. However, mgnetic ctution requires components tht re reltively lrge compred to proposed MEMS device. On or h, electrosttic ctution ws found to be suitble for trgeted dimensions. In ddition, electrosttic ctution does not require ny DC current refore suits power requirements ppliction. selection output wveguides cn n be controlled through electrosttic ctutors usg strd high voltge driver (e.g., [37]). Besides plnr rottion tht chieved with bi-directionl comb ctutor shown 1, two dditionl functions were implemented MEMS structure to improve performnce whole MOEMS system. first one described previously Section 2.1 bility to close gp between movble nchored prt MEMS, consequently reduce opticl losses ssocited with crossg ir gp. second feture tht ws implemented ltch tht enbles cpbility selectg n output chnnel (i.e., wveguide) holdg rottg structure position. Th relevnt for mny pplictions, cludg telecommunictions, where MEMS needs to rem fixed position for long periods. Th llows for device to be used without n ctution voltge fter lockg it position, consequently svg power. Moreover, ltch system needs be protected from potentil power (i.e., ctution voltge) filure by usg ltch lock tht secures ltch position order to keep opticl communiction ctive through selected chnnel. oreticl electrosttic equtions pull- voltge pproximtion were used s strtg pots to crete different ctutor designs rottionl ctutor, gp closer, ltch, ltch lock. se designs were n optimized usg fite-element methods (FEM) simultions. device designs re outled followg section. 3. Device Designs 3.1. Rottionl Actutors MEMS rottionl ctutors re required to chieve wide ngulr motion, order to llow for lrge number wveguides to be supported by 1 N switch. structures lso need to be compct fst to chieve smll system footprt sufficiently high switchg speed.
Micromches 2017, 8, 354 5 18 19 Every design cludes micro-pltform with rdius 300 µm coverg n rc 135. All Three prototypes different presented ctutor here structures feture were 3 µm designed wide 70 optimized µm long for nchor mximum tht lso dplcement serves s by flexurl usg sprg. both FEMse simultions nchor dimensions experimentl were selected vlidtion. to chieve FEM simultions good trde-f were between crried-out qulity usg stwre rottionl ANSYS motion (version 18.0, ctution ANSYS, voltge. Inc., Cnonsburg, In ddition, PA, USA). itil pltform hs been built with 45 fcet As demonstrted one side to byfcilitte results subsequent reportedopticl below, tests position usg MEMS virtul structurl pivot ssumed lyer to guide light. designmoreover, circulr strtegiclly comb drive plced hs dimples significnt were impct dded on on ech qulity design to ct motion s stoppers (i.e., howfor close rottion it cn follow pltform, perfect circle) thus preventg on comb ctutor drivewith geometry. movble remg fgers to prt collpse. th section presents first detiled design description implemented geometry shown different 2. ctutors circulr comb vestigted drive for th th design pltform. ws creted experimentl by ssumg mesurements tht pivot repot dcussed Section middle 5. nchor. Ech circulr fger hs width Every 10 design µm cludes order to hve micro-pltform sufficient structurl with rdius strength. 300 µmsymmetry coverg n rc rottion 135. All prototypes circulr comb, presented which here consequence feture 3 µm wide bendg 70 µm long nchor, nchor ws tht compensted lso serves s by cretg flexurl symmetric sprg. sespcg nchoron dimensions both sides were selected fgers to to chieve mke sure good tht trde-f ctution between blnced qulity to prevent rottionl untentionl motion erly ctution electrosttic voltge. pull-. In ddition, terior itil gp (i.e., pltform one hsclosest been built to with mirror) 45 between fcet on one side movg to fcilitte fixed subsequent fgers on opticl left tests ctutor usg 9 µm MEMS wheres structurl outer lyer gp to(i.e., guide light. one closest Moreover, to strtegiclly ltch) 13 plced µm. dimples On right were dded side, onterior ech design to outer ct s gps stoppers re 10 for µm rottion 12 µm, respectively. pltform, Th thusmkes preventg pitch ctutor between with two consecutive movble fgers on to collpse. eir movg comb or fixed first comb design to be implemented 42 µm. totl shown length mst 2. 650 circulr µm comb drive longest th fger design externl ws edge creted positioned by ssumg t 583 thtµm, both pivot mesured pot from middle edge nchor. Ech circulr fger hs width 10 second µm design order to hve shown sufficient structurl 2b ( strength. one sided circulr symmetry comb). In th rottion version, rottion circulr comb, pivotl which pot ws consequence positioned t 2/3 bendg length nchor, ws from compensted nchored by edge cretg bsed on symmetric simultions, spcg s opposed on bothto sides middle fgers nchor to mke sure tht first design. ctution fl blnced position to prevent rottion untentionl pot ws obted erly electrosttic through n itertive pull-. nlys terior gp simultion (i.e., one results, closest to result mirror) between good greement movgwith similr fixed fgers works on presented left ctutor literture 9 µm[23]. wheres center outer pot gp used (i.e., to crete one closest circulr to comb ltch) drive 13 ws µm. n Onmoved right to side, new pivotl terior pot. outer dtnce gps re between 10 µm edge 12 µm, respectively. nchor Th mkes externl pitch edge between longest two consecutive fger th fgers design on eir 655 µm. movg width comb or fgers fixedws comb cresed to be 42 to µm. 12 µm totl order length to crese mst ir strength 650 µm reduce longest ir fger flexurl externl bendg. edge positioned pitch between t 583 fgers µm, both 46 mesured µm th from design. edge nchor. () (c) 2. 2. Microgrphs Microgrphs : : () () itil itil design, design, 2nd 2nd version version one-sided one-sided optimized optimized ctutor ctutor design, (c) 3rd version two-sided ctutor ctutor design. design. third design, illustrted 2c, uses sme estimted rottion pot (2/3 second design shown 2b ( one sided circulr comb). In th version, rottion length nchor) tht llows device to rotte lmost perfectly. right side ctutor ws pivotl pot ws positioned t 2/3 length nchor from nchored edge bsed on dded order to double rottion ngle. m mst holdg ctutor fgers 700 µm simultions, s opposed to middle nchor first design. fl position rottion long 12 µm wide to prevent bendg. longest fgers re positioned t 600 µm from pot ws obted through n itertive nlys simultion results, result good nchor remg fgers re eqully spced by 29 µm. width ech fger 12 µm s greement with similr works presented literture [23]. center pot used to crete second design. dtnce between rottionl fixed fgers ws optimized to chieve circulr comb drive ws n moved to new pivotl pot. dtnce between edge lrgest ngulr dplcement possible by preventg ny premture contct between movg nchor externl edge longest fger on th design 655 µm. width fgers sttic fgers. se dtnces re more ggressive compred to two previous design ws cresed to 12 µm order to crese ir strength reduce ir flexurl bendg. pitch vry from 7 µm to 10 µm. A stopper ws implemented t top mst usg 3 µm rdius between fgers 46 µm th design. dimples to prevent stiction structure. ctutors re designed to llow free rottion third design, illustrted 2c, uses sme estimted rottion pot (2/3 length over 10 ech direction without pull-. nchor) tht llows device to rotte lmost perfectly. right side ctutor ws dded Note tht bck fcet pltform ws modified s shown 3 such tht outer order to double rottion ngle. m mst holdg ctutor fgers 700 µm long terfce mirror to be dded bove micro-pltform focuses reflected light bem output wveguide order to suit 1 N switch ppliction.
Micromches 2017, 8, 354 6 19 Ltch 12 µm wide to prevent bendg. longest fgers re positioned t 600 µm from nchor remg fgers re eqully spced by 29 µm. width ech fger 12 µm s second design. dtnce between rottionl fixed fgers ws optimized to chieve lrgest ngulr dplcement possible by preventg ny premture contct between movg sttic fgers. se dtnces re more ggressive compred to two previous design vry from 7 µm to 10 µm. A stopper ws implemented t top mst usg 3 µm rdius dimples to prevent stiction structure. ctutors re designed to llow free rottion over 10 ech direction without pull-. Note tht bck fcet pltform ws modified s shown 3 such tht outer Micromches 2017,mirror 8, 354 to be dded bove micro-pltform focuses reflected light bem 6 18 terfce output wveguide order to suit 1 N switch ppliction. Three dditionl dditionl structures structures were were dded dded to to third third design design itertion: itertion: ltch, ltch, ltch ltch lock, lock, Three gp closer. 3b shows scnng electron microscope (SEM) microgrph whole device gp closer. 3b shows scnng electron microscope (SEM) microgrph whole device cludg dded dded structures. structures. Zoomed shown 3, 3, cludg Zoomed imges imges ltch ltch ltch ltch lock lock re re shown wheres gp closer shown 3c with zoomed view its sprgs 3d. wheres gp closer shown 3c with zoomed view its sprgs 3d. ltch ltchltch lock ltch lock structures llow micro-pltform lock tposition cert position without structures llow micro-pltform to lock t to cert without requirg requirg voltge bis. se structures re described followg subsections. voltge bis. se structures re described followg subsections. teeth Dimple Dimple 375 µm sprgs F2 Ltch F2 () (c) (d) 3. Scnng electron microscope (SEM) microgrphs third design: () ltch ltch lock, 3. device Scnng electron microscope (SEM) microgrphs third design: () ltch ltch whole illustrtg curved bck fcet, (c) gp-closg structure where yellow-dshed lock, whole device illustrtg curved bck fcet, (c) gp-closg structure where rrows show sprgs dplcements, green-dshed rrow shows gp closer resultg yellow-dshed rrows show sprgs dplcements, green-dshed rrow shows gp dplcement, (d) sprg. closer resultg dplcement, (d) sprg. 3.2. Ltch Ltch Lock 3.2. Ltch Ltch Lock ltch positioned t end ctutor mst. As shown on 3b, its lockg ltch positioned t end ctutor mst. As shown on 3b, its lockg mechnm consts set teeth tht follows curve described by mst circulr comb mechnm consts set teeth tht follows curve described by mst circulr comb drive durg rottion micro-pltform. Through electrosttic ctution, ltch trnsltes drive durg rottion micro-pltform. Through electrosttic ctution, ltch trnsltes towrds mst such tht two teeth t end mst lock side closest teeth towrds mst such tht two teeth t end mst lock side closest teeth ltch. lterntive would hve been to design ltch tht itilly locked position. However, ltch. lterntive would hve been to design ltch tht itilly locked position. th design would hve required 15 µm cvity t itil position structure to ensure tht it However, th design would hve required 15 µm cvity t itil position structure to would be relesed durg fbriction. Th clcultion done knowg tht mimum dimension ensure tht it would be relesed durg fbriction. Th clcultion done knowg tht tht cn be etched fbriction process used to implement prototypes 3 µm tht etch mimum dimension tht cn be etched fbriction process used to implement prototypes res must be defed t three positions round pir teeth defed t end mst: one 3 µm tht etch res must be defed t three positions round pir teeth defed t on both sides teeth one between m. Moreover, mimum feture size teeth end mst: one on both sides teeth one between m. Moreover, mimum lso 3 µm, mkg totl five times 3 µm, hence totl 15 µm width whole structure. feture size teeth lso 3 µm, mkg totl five times 3 µm, hence totl 15 µm length mst from nchor to ltch teeth ws set to 700 µm to leve dditionl spce width whole structure. length mst from nchor to ltch teeth ws set to 700 µm to leve dditionl spce for ltch ctutor beyond circulr comb drive. ltch teeth re 3 µm wide 11 µm long. To improve precion, y re designed to follow 714 µm rdius t ir bse 703 µm rdius t ir tip. All m re centered t micro-pltform rottion pot so tht mst teeth re lwys prllel to ltch teeth order to lock properly. ltch nchored through symmetricl support bems ctg s sprgs to enble directionl
Micromches 2017, 8, 354 7 19 for ltch ctutor beyond circulr comb drive. ltch teeth re 3 µm wide 11 µm long. To improve precion, y re designed to follow 714 µm rdius t ir bse 703 µm rdius t ir tip. All m re centered t micro-pltform rottion pot so tht mst teeth re lwys prllel to ltch teeth order to lock properly. ltch nchored through symmetricl support bems ctg s sprgs to enble directionl movement ltch. Ech bem 375 µm long 3.5 µm wide with 3 µm spcg between m. Th configurtion llows n ngulr ltchg precion 0.25 over entire motion pltform. ltch ctutor directionl comb drive mde 38 stright teeth 20 µm length spced by 3 µm. vilble dplcement spce front fgers side ctutor 12 µm. trnsltionl movement ltch limited by stopper to 11 µm. Th leves 1 µm spcg t mximum dplcement such tht even if ltch goes to pull-, it will not touch ctutor result short-circuit. ltch ctutors re symmetric positioned on both sides mst to ensure tht motion stble effective. An dditionl ltch lock structure ws dded to hold lock ltch to position with no pplied voltge. It positioned on ech side ltch mkes trnsltionl motion orthogonl to ltch. It cludes n 11 µm movble p locted t end 300 µm long 3 µm wide bem, s shown 3b. Th bem ctuted to llow dplcement ltch it n returned to its itil position to lock ltch when ltch ctution voltge removed. A dimple ws dded on side ech ctutor ltch lock to prevent stiction t pull-. se two structures operte simultneously to relese lock ltch. 3.3. Gp Closer gp closer enbles trnsltionl dplcement pltform towrds fixed prt substrte order to reduce ir gp between wveguides on ech side consequently mimize opticl losses. Two sets suspension sprgs lk ends micro-pltform to m mst s shown on 3c. positions ir nchors re designed to prevent ny dcontuity long bck-fcet pltform tht could cuse opticl losses for 1 N mirror-bsed switch ppliction. In ddition, ir positions llow relible trnsltionl motion pltform. It worth mentiong tht gp-closg movement towrds fixed prt wveguides mts rottion ngle. Ech suspension sprgs composed three bems tht re 205 µm long 3 µm wide. Th ensures miml lterl dplcement, which necessry for pltform to sit on dimples fter closg ir gp. Two 3 µm dimples ctg s stoppers were dded on both sides ctutor to prevent stiction or electricl contct pltform with sttic prt gp-closg ctutor, while mimizg gp. edges se two dimples re 3 µm wy from externl edge micro-pltform plced t cert dtnce from fixed prt contg wveguides llowg fl gps s low s 250 nm fter ctivtg ctutor. bck fcet pltform ws engeered to compenste divergence bem side plnr wveguide for 1 N mirror-bsed switch ppliction. For th purpose, 45 fcet ws replced by circulr bck fcet with 550 µm rdius fcg front fcet (s shown 3c), such tht comg light bem reflected by curved bck fcet focused bck to exit wveguides bove pltform. opticl losses due to divergence bem re thus mimized. rdius front fcet mirror remed 300 µm s or designs. 4. Test Setups test setup to chrcterize rottionl motion pltform shown 4. fbricted MEMS pltforms were tested usg probe sttion with four DC probes high-resolution cmer (Bsler Ace2000-340kc, Bsler AG, Ahrensburg, Germny) to cpture imges t different ctution voltges. One rottion ctutor connected to high voltge power source (SRS PS310/1250V-25W, Stnford Reserch Systems, Sunnyvle, CA, USA) with lrge restnce 100 MΩ series to prevent high current if ctutor touches structure ccidently durg dplcement. unused ctutors re ll grounded usg probes or wire bondg to ensure tht
Micromches 2017, 8, 354 8 19 y do not ccumulte chrges, which my result untentionl electrosttic forces ledg to undesired dplcement movble structures. probes re positioned on metl pds set Micromches pictures 2017, 8, n 354 tken, one for ech vlue ctution voltge. pictures re n 8 post 18 processed usg imge processg stwre, order to clculte ngulr motion for different environment usg custom mde vcuum chmber order to improve qulity fctor ctution voltges. Rottion or direction ws tested similrly by connectg voltge resonnce, sce qulity fctor device too low to llow for such mesurement to be source to opposite ctutor. or ctutors (i.e., ltch, ltch lock, gp closer) were tested done ir due to excessive ir dmpg. similr fshion. Micromches 2017, 8, 354 8 18 environment usg custom mde vcuum chmber order to improve qulity fctor resonnce, sce qulity fctor device too low to llow for such mesurement to be done ir due to excessive ir dmpg. 4. Test setup for rottionl ctution pltform. 4. Test setup for rottionl ctution pltform. test setup to chrcterize resonnt frequency pltform shown 5. resonnt frequency tests re done usg vector network nlyzer (VNA) (Agilent E5061B, Agilent Technologies, Snt Clr, CA, USA) custom prted circuit bord (PCB). Bis tees re used to bis structure to overly VNA signls. device die wire-bonded order to connect bisg AC signls required. resonnce mesurement performed 1 mtorr vcuum environment usg custom mde vcuum chmber order to improve qulity fctor resonnce, sce qulity fctor device too low to llow for such mesurement to be done ir due to excessive ir dmpg. 4. Test setup for rottionl ctution pltform. 5. Test setup for resonnt frequency mesurement pltform. For opticl mesurements, fbricted crossbr switch ws mounted on PCB wire bonded. bord ws plced between two 3-x micro-positiong stges holdg tpered lensed fibers it ws connected to two high voltge sources to control MEMS. Light from lser opertg t 1550 nm ws coupled to wveguides on chip output power ws mesured with power meter. put polriztion ws optimized with polriztion controller. 5. Results 5. Test 5. Test setup setup for for resonnt resonnt frequency frequency mesurement mesurement pltform. pltform. Prototype MEMS pltforms were fbricted commercil SOI process (SOIMUMPs from MEMSCAP, For For opticl opticl Crolles, mesurements, Frnce) [38]. fbricted Th fbricted process crossbr llows crossbr switch fbriction switch ws mounted ws mounted onmems PCBon itself, wire PCB but bonded. it does wire not bonded. bord clude ws plced bord opticl ws between stck plced bove twobetween 3-x MEMS micro-positiong two 3-x pltform. micro-positiong It stges noneless holdg stges llows tpered holdg to design lensed tpered fibers MEMS lensed it pltform, ws fibers connected it ws to tochrcterize two connected high voltge to its two motionl sources high voltge to performnce control sources MEMS. to control fetures Light from for MEMS. lser MOEMS Light opertg from system lser t described opertg t Section 1550 2.1. nm ws coupled to wveguides on chip output power ws mesured experimentl with power results meter. for put three polriztion designs described ws optimized bove re with presented polriztion th controller. section. Observtions on fbriction process re given Section 5.1. followg subsections present 5. mesured Results responses different fbricted structures. Note tht more mesurement detils re presented for third design s it represents optimized design for trgeted system. Prototype MEMS pltforms were fbricted commercil SOI process (SOIMUMPs from
Micromches 2017, 8, 354 9 19 1550 nm ws coupled to wveguides on chip output power ws mesured with power meter. put polriztion ws optimized with polriztion controller. 5. Results Prototype MEMS pltforms were fbricted commercil SOI process (SOIMUMPs from MEMSCAP, Crolles, Frnce) [38]. Th process llows fbriction MEMS itself, but it does not clude opticl stck bove MEMS pltform. It noneless llows to design MEMS pltform, to chrcterize its motionl performnce fetures for MOEMS system described Section 2.1. experimentl results for three designs described bove re presented th section. Observtions on fbriction process re given Section 5.1. followg subsections present mesured responses different fbricted structures. Note tht more mesurement detils re presented Micromches for 2017, 8, third 354 design s it represents optimized design for trgeted system. 9 18 5.1. Fbriction Process Chrcteriztion m rottion nchor nchor ws ws first lid first out lid with out three with different three different width vlues width 3 vlues µm (SOIMUMPs 3 µm technology (SOIMUMPs limittion), technology 3.5 limittion), µm 43.5 µm, µm sgle 4 µm, length sgle 80 length µm. In th 80 µm. fshion, In th fshion, criticl prmeters criticl prmeters nchorg structures nchorg cn structures be determed, cn be which determed, key to which rottionl key to motion rottionl pltform. motion A SEM pltform. microgrph A SEM shows microgrph tht shows resultg tht fbricted resultg nchors fbricted hvenchors widths hve 2.5 widths µm, s shown 2.5 µm, s shown 6, 3.2 µm 6, 3.9 3.2 µm, respectively. 3.9 µm, respectively. nchor 3.2 nchor µm proved 3.2 to µm beproved sufficiently to be strong sufficiently to provide strong to high provide fbriction high yield, fbriction while llowg yield, while for llowg wider rottion for wider for given rottion voltge for rnge given voltge compron rnge to compron 3.9 µm nchor. to Accordgly, 3.9 µm nchor. it ws Accordgly, selected s it ws reference selected nchor s width reference to use for nchor ll designs. width to use for ll designs. 6. SEM microgrph showg mesured nchor width. Knowg tht Young modulus, Poson s rtio sher modulus silicon chnge Knowg tht Young modulus, Poson s rtio sher modulus silicon chnge significntly with crystl orienttion [39,40], vestigtions impct se properties on significntly with crystl orienttion [39,40], vestigtions impct se properties on ctution voltge were done on fl design. ctution voltge were done on fl design. 5.2. 5.2. First Design Usg test test setup similr to to one one shown 4, 4, first first design design chieved chieved 2.1 2.1 rottion for for clockwe (CW) (CW) ctution t t 330 330 V 2.25 2.25 rottion for counter clockwe (CCW) ctution t t 330 330 V, V, s s shown shown 7. 7. It It importnt importnt to to dicte dicte tht tht fbriction fbriction th th design design ws ws crried crried out out <100> silicon silicon crystlle crystlle plne plne sce sce orienttion orienttion does does hve hve n n impct impct over over Young s modulus, modulus, sher sher constnt constnt Poson s Poson s rtio. rtio. non-optimized non-optimized rottion rottion pot pot comb comb drive drive cused cused fixed fixed mobile mobile fgers fgers to to touch, touch, which which limited limited rottion rottion ngle. ngle. As As expled expled bove, bove, rottion rottion pot pot ws ws corrected corrected to to prevent prevent th th problem problem second second third third designs. designs. ottion ( ) 2.5 C. Clockwe 2 Exp <100> 1.5 1 Clockwe
330 V, s shown 7. It importnt to dicte tht fbriction th design ws crried out <100> silicon crystlle plne sce orienttion does hve n impct over Young s modulus, sher constnt Poson s rtio. non-optimized rottion pot comb drive cused fixed mobile fgers to touch, which limited rottion ngle. As expled Micromches bove, rottion 2017, 8, 354 pot ws corrected to prevent th problem second third designs. 10 19 Rottion ( ) 2.5 C. Clockwe 2 Exp <100> 1.5 1 Clockwe 0.5 Sim <100> 0 300 200 100 0 100 200 300 Voltge (V) 7. Mesured simulted pltform ngulr dplcement for left right ctution 7. Mesured simulted pltform ngulr dplcement for left right ctution first design where + dt pots represent simulted dt, solid le fit to simulted Micromches first design 2017, where 8, 354 + dt pots represent simulted dt, solid le fit to simulted 10 18 dt, dt pots represent experimentl mesurements, dotted le fit to dt, dt pots represent experimentl mesurements, dotted le fit to 5.3. Second experimentl mesurements. experimentl Design mesurements. 5.3. Second second Design design implemented improved circulr comb ctutor design with optimized rottion pivotl pot. ctutor rottion ws chrcterized usg test setup shown second 4. design 8 shows implemented mesured improved rottion circulr ngle comb ctutor ctutor. design Th design with exhibits optimized 4 rottion mximum pivotl rottion pot. t 290 ctutor V for rottion fbriction ws followg chrcterized usg usg <100> test setup silicon shown crystlle 4. 8 shows mesured rottion ngle ctutor. Th design exhibits 4 pln. ctution voltge lower thn tht design 1 due to difference dimensions mximum rottion comb fgers. t 290 V for fbriction followg usg <100> silicon crystlle pln. ctution voltge lower thn tht design 1 due to difference dimensions comb fgers. 6 Rottion ( ) 5 4 3 2 Exp <100> 1 Sim <100> 0 0 100 200 300 Voltge (V) 8. 8. Mesured Mesured simulted simulted pltform pltform ngulr ngulr dplcement dplcement second second design design with with fittg fittg curves curves where where + + dt dt pots pots represent represent simulted simulted dt, dt, solid solid le le fit to fit to simulted simulted dt, dt, dt pots represent experimentl mesurements, dotted le fit to dt pots represent experimentl mesurements, dotted le fit to experimentl mesurements. experimentl mesurements. 5.4. Third Design circulr comb drive design third design proved to yield best results. ngulr dplcement reched 5 5 for ech side with 350 V ctution voltge when nchor defed prllel to <100> crystl plne silicon structurl lyer, which sme orienttion s or designs. Th resulted totl ngulr motion more thn 10 when both ctutors re used, s shown 9. 9. Moreover, mximum ngulr dplcement lmost doubles to rech 9.5 for ech side ctution voltge requiredto torech rechth th mximum 180 180V Vwhen when nchor nchor designed designed long long <110> <110> crystl crystl plne plne (rotted (rotted 45 45compred to to or or designs). designs). As As result, result, it becomes possible to cover totl more thn 19 s illustrted 9. Th due to notropic nture Young s modulus sgle-crystl silicon [39,40]. resonnt chrctertics pltform were obted usg test setup shown 5. fundmentl resonnt mode tht gp closer structure. two extrem resonnce mode shpe re illustrted 10. device exhibits resonnt frequency 2.68
Micromches 2017, 8, 354 11 19 it becomes possible to cover totl more thn 19 s illustrted 9. Th due to Micromches 2017, 8, 354 11 18 notropic nture Young s modulus sgle-crystl silicon [39,40]. C. Clockwe 10 9 Clockwe 8 Exp <110> 7 6 Exp <100> 5 4 Micromches 2017, 8, 354 3 11 18 Rottion ( ) Rottion ( ) 2 C. Clockwe 10 1 90 Sim Clockwe <100> 400 300 200 100 80 100 200 300 400 Exp <110> Voltge (V) 7 6 9. Pltform ngulr dplcement for left right ctution Exp third <100> design with fittg 9. Pltform ngulr dplcement for left right ctution third design with fittg curves showg more thn ±5 5 both sides for <100> nchor orienttion ±9.5 for <110> nchor curves showg more thn ±5 both sides for <100> 4 nchor orienttion ±9.5 for <110> nchor orienttion where dt pots represent simulted dt, solid le fit to simulted orienttion where dt pots represent simulted dt, solid le fit to simulted dt, + dt pots represent experimentl mesurements 3 on <100> fbriction plne, o dt, + dt pots represent experimentl mesurements on <100> fbriction plne, dt pots represent experimentl mesurements on 2 <110> fbriction plne, dotted les o dt pots represent experimentl mesurements on <110> fbriction plne, dotted re fit to experimentl mesurements. 1 Sim <100> les re fit to experimentl mesurements. 0 400 300 200 100 0 100 200 300 400 resonnt chrctertics pltformvoltge were (V) obted usg test setup shown 5. fundmentl resonnt mode tht gp closer structure. two extrem resonnce mode shpe9. re Pltform illustrted ngulr dplcement 10. for device left exhibits right ctution resonnt frequency third design 2.68 with khz fittg with qulity curves fctor showg 5.47more vcuum thn ±5 s both shown sides from for <100> mesured nchor orienttion trnsmsion ±9.5 curve for <110> nchor 11. Th vlueorienttion directlywhere lked to dt gp pots closer represent such tht simulted modifiction dt, solid to le gp closer fit to will simulted impct resonnt dt, frequency + dt pots MEMS. represent Aexperimentl modifictionmesurements mde to on nchors <100> fbriction gp closer plne, under vestigtion o dt pots to crese represent experimentl resonnt frequency mesurements set on it such <110> tht fbriction first plne, resonnt frequency dotted to pper les re one fit to comg experimentl from rottion mesurements. pltform, which close to 3.5 khz. () 10. Simulted resonnce structure: () First extremum, second extremum. -45 Trnsmsion (db) -55 () -65 f r = 2.67685 khz -75 loss=-51.205 db BW=489.762 Hz -45 Q=5.4656-85 1 2 3 4 5-55 f (khz) 10. Simulted resonnce structure: () First extremum, second extremum. Trnsmsion (db) 11. Mesured -65 resonnce chrctertics third design t 1 mtorr vcuum level. -75 f r = 2.67685 khz loss=-51.205 db BW=489.762 Hz Q=5.4656
() Micromches 2017,10. 8, 354 Simulted resonnce structure: () First extremum, second extremum. 12 19 Trnsmsion (db) -45-55 -65 fr = 2.67685 khz loss=-51.205 db BW=489.762 Hz Q=5.4656-75 -85 1 2 3 4 5 f (khz) Micromches 2017, 8, 354 11. Mesured resonnce chrctertics third design t 1 mtorr vcuum level. 11. Mesured resonnce chrctertics third design t 1 mtorr vcuum level. 12 18 5.5. Ltch Gp Closer 5.5. Ltch Gp Closer experimentl results gp closer yielded tht structure cn mimize ir gp gp closer tht structure cn V. mimize ir gp closeexperimentl 3.25 µmresults itil seprtion with yielded n ctution voltge 113 mesured pull- close 3.25 µm itil seprtion with n ctution voltge 113 V. mesured pull- voltge voltge bit lower thn FEM simultion results, s shown 12. simulted resonnt frequency bit lower thn simultion s shown 12. frequency simultedresonnt gpfem closer 4.30results, khz. experimentl resonnt 2.68 khzfrequency s stted gp closer 4.30 khz. experimentl resonnt frequency 2.68 khz s stted before. before. difference between simultion mesured results pull- voltge difference between simultion mesured results pull- voltge resonnce resonnce frequency cn be ttributed to fct tht width fbricted nchors gp frequency cn be ttributed to fct thtwhich width fbricted closer closer re thner thn designed width results lower sprgnchors constnts. Nogp stiction re thner thn designed width which results lower sprg constnts. No stiction pltform pltform ws observed durg mesurements, it ws free to open close rpidly ws observed durg it ws free to open close rpidly repetedly durg repetedly durg mesurements, experimentl tests. experimentl tests. Exp <100> Dplcement (µm) 3 2 1 Sim <100> 0 0 20 40 60 80 100 120 140 Voltge (V) 12. 12. Simultion Simultion experimentl experimentl gp gp closer closer dplcement dplcement vs vs ctution ctution voltge voltge for for<100> <100> nchor dt dt pots pots represent represent simulted simulted dt, dt, solid solid le le nchor orienttion orienttion where where fit fit to to simulted dt, + dt pots represent experimentl mesurements. simulted dt, + dt pots represent experimentl mesurements. Moreover, experimentl experimentl results results ltch ltch ltch ltch lock lock vlidted vlidted opertion opertion Moreover, structures. 13 shows itil ltched positions ltch teeth. dplcement structures. 13 shows itil ltched positions ltch teeth. dplcement neededto tirmly firmlylock lock teeth teeth ltch bout 7 µm dplcement needed to pull needed ltch bout 7 µm dplcement needed to pull ltch ltch lock wy from ltch 3 µm. resultg mesured ctution voltge for ltch 40 V lock wy from ltch 3 µm. resultg mesured ctution voltge for ltch 40 V ctution ctution voltge forltch ltch V. Both se voltges regood good greement voltge for lock lock 30V.30 Both se voltges re greement withwith simultions s demonstrted s 14,b. Simultion results yield resonnt simultions s demonstrted 14,b. Simultion results yield resonnt frequencyfrequency 2.99 khz 2.99 khz for ltch structure. for ltch structure.
structures. 13 shows itil ltched positions ltch teeth. dplcement needed to firmly lock teeth ltch bout 7 µm dplcement needed to pull ltch lock wy from ltch 3 µm. resultg mesured ctution voltge for ltch 40 V ctution voltge for ltch lock 30 V. Both se voltges re good greement with simultions s demonstrted s 14,b. Simultion results yield resonnt frequency Micromches 2017, 8, 354 13 19 2.99 khz for ltch structure. () Micromches 2017, 8, 354 13 18 13. 13. Lockg Lockg mechnm: mechnm: () () Initil Initil position position ltched ltched position. position. 5 Dplcement (µm) Dplcement (µm) 8 Exp <100> 6 4 2 Sim <100> 10 20 30 40 3 Exp <100> 2 1 Sim <100> 0 0 4 50 Voltge (V) () 0 0 5 10 15 20 Voltge (V) 25 30 35 14. 14. Ltch for <100> <100> nchor open open Ltch ctution ctution for nchor orienttion orienttion showg showg () () locked locked ltch ltch t t 40 40 V V lock t 30 V where solid le fit to simulted dt, dotted le fit to lock t 30 V where solid le fit to simulted dt, dotted le fit to experimentl dt. experimentl dt. 5.6. Opticl Crossbr Crossbr Switch Switch Cell Cell 5.6. Opticl Mesurements Mesurements As n n exmple results from from crossbr crossbr switch switch cell cell implemented implemented usg usg As exmple ppliction, ppliction, mesurement mesurement results optimized rottg pltform design re presented to demonstrte vibility proposed optimized rottg pltform design re presented to demonstrte vibility proposed system. custom micrbriction micrbriction technology technology volvg mixture system. switch switch ws ws fbricted fbricted custom volvg mixture surfce bulk bulk micromchg micromchg to to tegrte tegrte wveguides wveguides MEMS MEMS structures. structures. surfce A simplified fbriction process flow th cross br switch cell illustrted A simplified fbriction process flow th cross br switch cell illustrted 15 15 [36]. [36]. process strts with n SOI wfer with 25 µm silicon device lyer. First, 4 µm lyer silicon process strts with n SOI wfer with 25 µm silicon device lyer. First, 4 µm lyer silicon dioxide 200 dioxide 200 nm nm lyer lyer silicon silicon nitride nitride re re deposited deposited through through plsm-enhnced plsm-enhnced chemicl chemicl vpor vpor deposition (PECVD) formg bottom clddg core lyer wveguides, deposition (PECVD) formg bottom clddg core lyer wveguides, respectively. respectively. n, silicon silicon nitride ptterned usg e-bem lithogrphy wveguides. n, nitride ptterned usg e-bem lithogrphy to defe to defe wveguides. Afterwrds, Afterwrds, 4 µm lyer PECVD silicon dioxide deposited ptterned usg hrd chromium 4 µm lyer PECVD silicon dioxide deposited ptterned usg chromium (Cr) msk (Cr) hrd msk rective ion etchg (RIE) gog through both bottom top clddgs. rective ion etchg (RIE) gog through both bottom top clddgs. A 300 nm lyer A 300 nm lyer lumum wet nptterned sputteredto wet to form pds for electricl lumum nsputtered form ptterned pds for electricl contcts. se steps contcts. se steps result structure shown 15. Chromium hrd msks for result structure shown 15. Chromium hrd msks for ptterng top structures ptterng top structures n bottom releseusg trenches re nsptterned dry etchg s bottom relese trenches re ptterned dry etchg shown usg 15b. Relese shown 15b. Relese trenches re n deep RIE etched through Cr msk on bottom trenches re n deep RIE etched through Cr msk on bottom side. n, Cr msk dry side. n, Cr msk photorest dry stripped pplied protective photorest pplied to lyer top stripped protective lyer to top side.lyer buried oxide side. n buried oxide lyer n wet etched 49% hydrluoric cid while top protected by wet etched 49% hydrluoric cid while top protected by photorest lyer, s shown photorest lyer, s shown 15c. Afterwrds, photorest stripped from lyer 15c. Afterwrds, photorest lyer stripped lyer lyer polymer deposited polymer deposited from bckside to hold structures plce fter etchg. n, bckside to hold structures plce fter etchg. n, structures re dry etched from top structures re dry etched from top side usg Cr msk to go through wveguide lyers structurl silicon order to defe opticl fcets MEMS structures, s illustrted 15d. structures re flly relesed oxygen plsm to remove polymer, s shown 15e. Moreover, wveguides re mde 200 nm-thick 1.5 µm-wide silicon nitride core, ensurg sgle TE mode opertion. Inverted tpers where core nrrows down to 494 nm re
Micromches 2017, 8, 354 14 19 side usg Cr msk to go through wveguide lyers structurl silicon order to defe opticl fcets MEMS structures, s illustrted 15d. structures re flly relesed oxygen plsm remove polymer, s shown 15e. Micromches 2017,to 8, 354 14 18 Micromches 2017, 8, 354 14 18 15. Simplified Simplified process process flow flow () () silicon-on-sultor silicon-on-sultor (SOI) (SOI) with with ptterned ptterned wveguides wveguides Al Al 15. pds, front front bck bck ptterned ptterned Cr Cr msk, msk, (c) (c) front front protective protective lyer lyer bckside bckside etch, etch, (d) (d) bckside bckside pds, polymer deposition micro-opto-electro-mechnicl systems (MOEMS) etch, (e) MOEMS relese polymer deposition micro-opto-electro-mechnicl systems (MOEMS) etch, (e) MOEMS relese by by strippg polymer [33]. strippg polymer [33]. Moreover, wveguides re mde 200 nm-thick 1.5 µm-wide silicon nitride core, ensurg sgle TE mode opertion. Inverted tpers where core nrrows down to 494 nm re locted t edges chip wheres on ech side gp tpers re 406 nm wide to improve couplg with lensed fibers mimize loss due to bem expnsion, respectively. mode overlp Simplified process modl flow ()overlp silicon-on-sultor (SOI) with ptterned wveguides Al nlys ws15. done usg opticl simultion verted tpers length optimiztion pds, front bck ptterned Cr msk, (c)expnsion front protective lyer etch, (d) were bckside ws obted usg bidirectionl EigenMode nlys; bothbckside optimiztions crried deposition micro-opto-electro-mechnicl systems (MOEMS) etch,bc, (e) MOEMS out polymer Lumericl MODE stwre (version 2017b, Lumericl Inc., Vncouver, Cnd).relese 16 bystrippg polymer [33]. shows SEM microgrph fbricted switch [33]. 16. SEM microgrph fbricted crossbr switch [33]. For opticl mesurements, light ws jected to chip from lser opertg t wvelength 1550 nm. lser ws connected to polriztion controller lensed tpered fiber with n output bem dimeter 2.5 µm. output signl ws collected with similr lensed tpered fiber mesured with power meter. put polriztion stte ws optimized with polriztion controller to mximize output signl. For current design, th should correspond to fundmentl TE mode. Both lensed tpered fiber were mounted onto 3-x micro-positiong stges to lign m to device under test. In br stte, both pths showed totl sertion loss 14.8 db once gp ws closed (to 16. SEM microgrph fbricted crossbr switch [33]. 500 nm fl gp th device version). Th vlue cludes couplg losses out chip, propgtion 2 mm, losses jected remg 500 nm wide gps on ech side t For losses opticllong mesurements, light lser lser opertg For opticl mesurements, light ws ws jected to to chip chip from from opertg t pltform. Furr development fbriction process ongog to improve fiber couplg wvelength 1550 nm. lser ws connected to polriztion controller lensed tpered wvelength 1550 nm. lser ws connected to polriztion controller lensed tpered qulity wveguides. Closg gp order for pltform ls on dimples fiber with n output bem dimeter 2.5 µm. output signl ws collected with similr lensed required 105 V. tpered fiber mesured with power meter. put polriztion stte ws optimized with Switchg pltform to cross stte ppliction 118 Vdesign, on comb drive. polriztioncontroller mximize required output signl. For current th should With gptoclosed, totl sertion loss ws 12.2lensed db. With gp open mounted loss ws 24.5 db,3-x thus correspond fundmentl TE mode. Both tpered fiber were onto gp-closg mechnm improves performnce by more thn 12 db. Th excess loss due to micro-positiong stges to lign m to device under test.
Micromches 2017, 8, 354 15 19 fiber with n output bem dimeter 2.5 µm. output signl ws collected with similr lensed tpered fiber mesured with power meter. put polriztion stte ws optimized with polriztion controller to mximize output signl. For current design, th should correspond to fundmentl TE mode. Both lensed tpered fiber were mounted onto 3-x micro-positiong stges to lign m to device under test. In br stte, both pths showed totl sertion loss 14.8 db once gp ws closed (to 500 nm fl gp th device version). Th vlue cludes couplg losses out chip, propgtion losses long 2 mm, losses remg 500 nm wide gps on ech side pltform. Furr development fbriction process ongog to improve fiber couplg qulity wveguides. Closg gp order for pltform ls on dimples required 105 V. Switchg pltform cross stte required ppliction 118 V on comb drive. With gp closed, totl sertion loss ws 12.2 db. With gp open loss ws 24.5 db, thus gp-closg mechnm improves performnce by more thn 12 db. Th excess loss due to greter seprtion between wveguides s well s mlignment between movg fixed prt switch when gp open. crosstlk ws below 40 db both sttes. Propgtion losses 0.8 db/cm on similr wveguide configurtion were clculted experimentlly test structures vilble from previous fbriction runs, which contribute for t lest 0.2 db loss ctul mesurements. oreticlly, opticl loss over ech 500 nm ir gp ws simulted to be bout 1.7 db. In ddition, typicl fiber couplg to chip test setup contributes mimum 3 db per fiber to sertion loss. miml loss budget clculted for device for two gps, two fiber couplg propgtion loss wveguides n 9.6 db, which -le with mesured loss, especilly notg tht lignment losses could be higher thn mimum. se loss estimtes could not be confirmed experimentlly becuse no chrcteriztion wveguides were fbricted onto chip. It worth mentiong tht proposed pltform lso suitble for or opticl pplictions, for exmple 1 N switch proposed 1b [29,30]. Notbly, wveguides ptterns cn be designed optimized dependently MEMS pltform design to use sgle mode opertion or polriztion dependent wveguides. 6. Dcussion Three different micro-pltform designs were implemented tested, ech with prticulr chrctertics. first design demonstrted little more thn 4 ngulr motion usg ctutors on both sides lso showed tht motion side comb drive ws not optimized erly pull- ws observed between fixed movble fgers. second design improved comb gve more stble control micro-pltform over n ngulr coverge 4 one direction. third design implementg bidirectionl optimized circulr comb ctutor fbricted with n nchor long <100> crystl orienttion (sme s previous designs) demonstrted ±5 ngulr dplcement. Moreover, sme design fbricted with nchor long <110> crystl plne demonstrted significnt dvntges over or two designs with respect to nchor flexibility dplcement. An ngulr dplcement ±9.5 ws mesured with pull--free opertion. Th design thus enbles prece control pltform over its entire circulr dplcement. Tble 1 compres designs presented here to or stte---rt rotry ctutors. design presented here chieves highest rottion ngle to dte. third design lso cludes dditionl fetures: ltch, ltch lock, gp closer, circulr bck fcet. se fetures re useful for relizg trgeted opticl systems presented Section 2.1. design relized reltively compct footprt 1.3 mm by 1 mm.
Micromches 2017, 8, 354 16 19 Tble 1. Compron MEMS Rottionl Electrosttic Actutors. Reference Rottion Angle ( ) Actution Voltge (V) Are (mm 2 ) Resonnce Frequency (Hz) [19] ±9 60 1 1 410 [23] 4.7 75 1.5 0.6 N/A [24] 2.8 100 ~2 0.5 N/A [25] ±1.5 190 ~2 1 ~1 k [26] 3 130 2 1 246 [27] ~±0.8 50 ~0.6 0.6 ~8 11.1 k Notes Serpente flexures used to crese rottion ngle t expense reduced opertg speed. A rel pivot formed by double-clmped bem ws utilized for rottionl tung structures MEMS tunble lsers. A movble rm 2 mm long forms m rottg structure cn be relibly operted kilohertz rnge. Actutors with movble rms 1.2 1.5 mm with virtul pivotl pot rottion for externl cvity tunble lsers. Long-rm (>5 mm) comb-drive rotry ctutor with n externlly mounted lrge mirror for opticl pplictions. MEMS switch bsed on rotry electrosttic comb ctutor. [28] 2 100 ~2.5 2 10.268 k Microgripper bsed on rotry comb ctutor. Th work ±9.5 180 1.3 1 2.68 k Circulr comb ctutor with ltch lock gp-closg mechnms for reconfigurble low-loss -plne tegrted optics. 7. Conclusions Th work presented different MEMS rottionl micro-pltform designs imed t tegrtion with opticl wveguides order to implement MOEMS system tht enbles control propgtion direction light bem wveguides. presented micro-pltform controlled by circulr rottionl electrosttic ctutor. Beyond rottion, pltform fetures n ir gp-closg mechnm tht contributes to provide low constnt opticl losses t ny ngulr position pltform. It lso fetures ltch mechnm to secure position pltform without requirg DC bisg voltge when pproprite rottion chieved. ltch structure llows holdg pltform position with resolution 0.25 over entire ngulr rnge motion. gp-closg structure reduces itil 3 µm ir gp to fl gp s low s 250 nm usg DC ctution voltge 113 V. Dimples re utilized design s stoppers for different structures order to prevent stiction ctutors, thus enblg relible control. device demonstrted experimentlly free or ltched plne bidirectionl ngulr motion up to 19 usg 180 V electrosttic ctution. experimentl resonnt frequency m device 2.68 khz, which llows n opertion speed on order ~300 µs. pltform ws tegrted with silicon nitride wveguides usg custom micrbriction technology to crete crossbr opticl switch s n exmple ppliction prelimry mesurement results were reported. switch opertes t DC voltge 118 V, which required to chieve necessry 5 rottion. In br stte, switch exhibits totl sertion loss 14.8 db with gp closed to 500 nm through electrosttic gp-closg mechnm. In cross stte, switch exhibits totl sertion loss 24.5 db with open gp, reducg to 12.2 db when gp closed. Thus, gp-closg mechnm improves performnce by more thn 12 db. crosstlk ws mesured to be below 40 db both sttes. performnce device will be improved by reducg fl gp pltform to 250 nm n 100 nm, which will oreticlly lower MEMS ir gp sertion loss to bout 0.1 db. To uthors knowledge, th first opticl switch bsed on rottg MEMS device with tegrted silicon nitride wveguides reported to dte.
Micromches 2017, 8, 354 17 19 Acknowledgments: uthors would like to thnk CMC Microsystems for providg stwre tools enblg device fbriction. uthors lso thnk AEPONYX Inc., Nturl Sciences Engeerg Reserch Council Cnd (NSERC), Regroupement Strtégique en Microsystèmes du Québec (ReSMiQ) for ir fncil support. uthors would like to thnk Frnço Ménrd AEPONYX for h contribution to ide tegrtg multiple wveguides onto pltform. Author Contributions: Jonthn Briere Mrt Berrd designed experiments; Mohnnd Y. Elsyed Menouer Sidni fbricted devices. Jonthn Briere, Mohnnd Y. Elsyed Hdi Rbbni-Hghighi performed experiments nlyzed dt; Philippe-Olivier Beulieu lid out subset MEMS devices; Frederic Nbki Michël Menrd contributed experte, direction, mterils nlys tools. Conflicts Interest: uthors declre no conflict terest. References 1. Wu, M. Micromchg for Opticl Optoelectronic Systems. Proc. IEEE 1997, 85, 1833 1856. [CrossRef] 2. Li, G.; Yo, J.; Thcker, H.; Mek, A.; Zheng, X.; Shub, I.; Luo, Y.; Lee, J.; Rj, K.; Cunnghm, J.E.; et l. Ultrlow-loss, high-density SOI opticl wveguide routg for mcrochip terconnects. Opt. Express 2012, 20, 12035 12039. [CrossRef] [PubMed] 3. Bogerts, W.; Selvrj, S.K.; Dumon, P.; Brouckert, J.; de Vos, K.; vn Thourhout, D.; Bets, R. Silicon-on-sultor spectrl filters fbricted with CMOS technology. IEEE J. Sel. Topics Quntum Electron. 2010, 16, 33 44. [CrossRef] 4. Ford, J. Opticl MEMS: Legcy telecom boom. In Proceedgs Solid-Stte Sensors, Actutors Microsystems Workshop, Hilton Hed Isl, SC, USA, 6 10 June 2004; pp. 1 3. 5. Rhim, M.; Akkry, P.; Jmledde, N.; Nbki, F.; Menrd, M. An tegrted silicon-on-sultor contully tunble opticl dely le for opticl coherence tomogrphy. In Proceedgs 2013 IEEE 56th Interntionl Midwest Symposium on Circuits Systems (MWSCAS), Columbus, OH, USA, 4 7 August 2013; pp. 709 712. 6. Kle, E.J.; Geuzebroek, D.H.; Keldermn, H.; Sengo, G.; Bker, N.; Driessen, A. Reconfigurble opticl dd-drop multiplexer usg microrg resontors. IEEE Photonics Technol. Lett. 2005, 17, 2358 2360. [CrossRef] 7. Boysel, R.M.; McDonld, T.G.; Mgel, G.A.; Smith, G.C.; Leonrd, J.L. Integrtion deformble mirror devices with opticl fibers wveguides. Proc. SPIE 1993, 1793, 34 39. 8. L, P.-Y.; Hsieh, H.-T.; Su, G.-D.J. Design fbriction lrge-stroke MEMS deformble mirror for wvefront control. J. Opt. 2011, 13, 055404. [CrossRef] 9. Iked, M.; Goto, H.; Skt, M.; Wkbyshi, S.; Imnk, K.; Tkeuchi, M.; Yd, T. Two dimensionl silicon micromched opticl scnner tegrted with photo detector. Proc. SPIE 1995, 2383, 118. 10. Miller, R.; Burr, G.; Ti, Y.; Pslt, D. Electromgnetic MEMS scnng mirrors for hologrphic dt storge. In Proceedgs Solid-Stte Sensors, Actutors Microsystems Workshop, Hilton Hed Isl, SC, USA, 3 6 June 1996; pp. 183 186. 11. Seok, T.J.; Quck, N.; Hn, S.; Muller, R.S.; Wu, M.C. Lrge-scle brodb digitl silicon photonic switches with verticl dibtic couplers. Optic 2016, 3, 64 70. [CrossRef] 12. Hn, S.; Seok, T.J.; Quck, N.; Yoo, B.; Wu, M.C. Lrge-scle silicon photonic switches with movble directionl couplers. Optic 2014, 2, 370 375. [CrossRef] 13. Akihm, Y.; Hne, K. Sgle multiple opticl switches tht use freestg silicon nnowire wveguide couplers. Light Sci. Appl. 2012, 1, e16. [CrossRef] 14. Toshiyoshi, H.; Fujit, H. An electrostticlly operted torsion mirror for opticl switchg devices. In Proceedgs 8th Interntionl Conference on Solid-Stte Sensors Actutors, Stockholm, Sweden, 25 29 June 1995; pp. 297 300. 15. Petersen, K. Silicon torsionl scnng mirror. IBM J. Res. Dev. 1980, 24, 631 637. [CrossRef] 16. Du, H.; Cho, F.; Zhou, G. Mechniclly-tunble photonic devices with on-chip tegrted MEMS/NEMS ctutors. Micromches 2016, 7, 69. [CrossRef] 17. Chollet, F. Devices bsed on co-tegrted MEMS ctutors opticl wveguide: A review. Micromches 2016, 7, 18. [CrossRef]
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Micromches 2017, 8, 354 19 19 39. Kim, J.; Cho, D.-I.; Muller, R.S. Why (111) silicon better mechnicl mteril for mems? In Proceedgs Interntionl Conference on Solid-Stte Sensors Actutors, Munich, Germny, 10 14 June 2001; Trnsducers 01 Eurosensors XV, pp. 662 665. 40. Hopcrt, M.; Nix, W.; Kenny, T. Wht Young s modulus silicon? J. Microelectromech. Syst. 2010, 19, 229 238. [CrossRef] 2017 by uthors. Licensee MDPI, Bsel, Switzerl. Th rticle n open ccess rticle dtributed under terms conditions Cretive Commons Attribution (CC BY) license (http://cretivecommons.org/licenses/by/4.0/).