Demonstration of a stable ultrafast laser based on a nonlinear microcavity

Transcription

1 Reeive 9 Sep Aepte 8 Fe Pulishe 3 Apr DOI:.38/nomms76 Demonstrtion o stle ultrst lser se on nonliner mirovity M. Peinti,, A. Psquzi, Y. Prk, B.E. Little 3, S.T. Chu 3,4, D.J. Moss,5 & R. Mornotti Ultrshort pulse lsers, operting through the phenomenon o moe-loking, hve h signiint role in mny ets o our soiety or 5 yers, or exmple, in the wy we exhnge inormtion, mesure n ignose iseses, proess mterils, n in mny other pplitions. Reently, high-qulity resontors hve een exploite to emonstrte optil oms. The ility to phse-lok their moes woul llow moe-loke lsers to eneit rom their high optil spetrl qulity, helping to relize novel soures suh s preision optil loks or pplitions in metrology, teleommunition, mirohip-omputing, n mny other res. Here we emonstrte the irst moe-loke lser se on mirovity resontor. It opertes vi new moe-loking metho, whih we term ilter-riven our-wve mixing, n is se on CMOS-omptile high qulity tor miroring resontor. It hieves stle sel-strting osilltion with negligile mplitue noise t ultrhigh repetition rtes, n spetrl linewiths well elow 3 khz. INRS-EMT, 65 Blv. Lionel Boulet, Vrennes Quée, J3X S Cn. IPCF-CNR, UOS Rom n ISC-CNR UOS Monteliretti, Vi ei Turini 9, 85 Rom, Itly. 3 Ininer Lt, 69 Jv Drive, Sunnyvle, Cliorni 9489, USA. 4 Deprtment o Physis n Mterils Siene, City University o Hong Kong. 5 CUDOS n the Institute o Photonis n Optil Siene (IPOS), Shool o Physis, University o Syney, Syney, New South Wles 6, Austrli. Corresponene n requests or mterils shoul e resse to A.P. (emil: lessi.psquzi@gmil.om). nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.

2 nture ommunitions DOI:.38/nomms76 Pssively moe-loke lsers hve generte the shortest optil pulses to te. Sel-supporting ultrshort optil pulses n e proue nturlly in these lsers, y the omplex nonliner intertions etween hromti ispersion, the Kerr nonlinerity n sturle gin 3,4. There is onsierle interest in hieving oth very high n lexile repetition rtes 5,6 t requenies well eyon the rnge o tive moe-loking, where the use o eletronis poses intrinsi limittions. Mny ierent pprohes hve een propose to hieve this, rnging rom very short lser vities with lrge moe requeny spings (or exmple, lrge ree spetrl rnge (FSR),7,8, where very high repetition rte is hieve y simply reuing the pulse roun-trip time, t the expense o line qulity), to shemes where multiple pulses re proue in eh roun trip 3,9,, pplie primrily to ire lsers. A pioneering pproh to the ltter ws introue in 997 y Yoshi et l., where Fry-Pérot ilter inserte in the min vity suppresses ll ut ew moes tht re perioilly spe, leing to trin o pulses with ontrolle repetition rte. This pproh ws susequently reinterprete in terms o the issiptive ourwve-mixing (FWM) prigm,, n sine then, high repetitionrte pulse trins hve een emonstrte y opting vritions o this metho 5. Although, in priniple, issiptive FWM shemes llow or trnsorm-limite pulses to e generte t repetition rtes not limite y the min lser vity, their stility still remins severe issue ommon prolem when multiple pulses irulte in vity. This is onsequene o the t tht the gin n nonlinerity require to sustin proper lsing tion neessitte the use o very long ire vity lengths. This, in turn, proues smller vity moe requeny spings o (typilly) ew meghertz or less, whih llows mny moes to osillte within the Fry Pérot ilter nwith. Beuse these moes hve rnom phses, their eting results in severe low-requeny noise tht proues extremely unstle opertion 4. In this pper, we report the irst moe-loke lser se on nonliner monolithi high-q (qulity) tor resontor. Our lser hieves extremely stle opertion t high repetition rtes while mintining very nrrow linewiths, thus leing to high-qulity pulse emission. The key point is tht this resontor is not simply use s ilter ut ts s the nonliner element s well 6, similr in spirit to optilly pumpe multiple wvelength osilltors se on high Q-tor resontors 6. Beuse o this twool entrl role o the nonliner ilter, we term this new moe-loking sheme ilter-riven our-wve mixing (FD-FWM). It opertes in wy tht is in strk ontrst to tritionl issiptive FWM shemes, where the nonliner intertion ours in the ire n is then iltere seprtely y liner Fry Pérot ilter. Results Generl etures o ilter-riven our-wve mixing lser. Our metho hs two immeite vntges. First, it is intrinsilly more eiient; in the lternte pproh, the nonliner mixing is usully perorme right ter the mpliition stge, in the point o the loop where the pulse energy is mximum. The liner iltering ollows the nonliner step, utting prt o the spetrl roening. In our esign, the iltering nnot e onsiere to e seprte rom the nonliner proess. As some requeny omponents simply o not survive in the ilter owing to estrutive intererene, they re not le to see the energy trnser proess towrs orien ns in the spetrum, onsequently reuing the generl power loss. Seon, it rstilly reues the min vity length, whih sustntilly inreses the min vity moe requeny sping, thus rmtilly inresing the lser stility, s, ielly, only one vity moe is now llowe to osillte within the ring resonne. The omintion o these tors enles our sheme to hieve stle opertion t high repetition rtes over lrge rnge o operting onitions, without ny extr stiliztion system. In ition, our FD-FWM sheme n intrinsilly proue muh nrrower linewiths thn ultrshort vity moe-loke lsers (tht osillte t similr repetition rtes), euse the long min vity results in muh smller Shwlow- Townes phse noise limit 3,4. Therml stility o ilter-riven our-wve mixing sheme. A urther key vntge o our pproh lies in the t tht the stle lsing regime is highly roust to externl (or exmple, therml) perturtions, tht re well-known prolem in resontor-se optil prmetri osilltors (OPOs) 7,. In OPOs, temperture vritions ue to the irulting power nturlly etune ilter resonnes with respet to n externl pumping soure. Although stiliztion mehnisms suh s therml loking hve een exploite to solve this prolem, they re ineetive ginst slow temperture rits, t whih oten les to the sitution where the OPO shuts own 5. Our pproh oes not suer rom this prolem s ll the osillting lines re tully moes o the min vity tht lse within the resontor resonnes. As the nonliner resontor is prt o the min vity, the hnges in the resontor optil pth inue y heting lso ontriute to hnge in the min vity length, whih in turn moertes the requeny mislignment etween ring n min vity moes. Moreover, the stle osilltion is sustine primrily y externl gin n it is otine t resontor input power levels in the mw rnge, out n orer o mgnitue lower thn the vlues normlly use to pump OPOs. The ring resontor heting issues re thereore reue. However, we oun tht the entrl lsing requeny ws epenent on the energy ouple in the ring, whih yiele vrition o the entrl requeny over the power t the input o the ring o pproximtely.67 pm mw. Lser set-up n opertion. The key omponent o the lser, the ring resontor, shown in Fig., is n integrte miroring resontor with Q tor o. million (res, 6) (estimte rom mesure linewith o 6 MHz), rite in CMOS-omptile hip pltorm 7,8 se on high-inex, ope-sili glss wveguie. The experimentl set-up is shown in Fig. (see Methos or etils). The miroring resontor is simply emee in stnr erium ope-ire loop vity (ting s the gin meium) ontining pssn ilter with nwith lrge enough to pss ll o the osillting lines, with the min purpose o ontrolling the entrl wvelength λ. A ely line is employe to ontrol the phse o the min vity moes with respet to the ring moes. To investigte the epenene o the lser perormne on the min vity length, we onute experiments with two lsers, one se on short-length erium-ope ire mpliier (EDFA) n the other se on long high-power erium ytterium ire mpliier (EYDFA), the ltter hving similr operting regime to issiptive FWM lsers, where long ire-se vities re neessry to ssure the Kerr nonlinerity require or moe-loke lser opertion. The two onigurtions thereore h signiintly ierent min vity lengths (3 n 33 m), tht is, ierent FSRs (68.5 n 6 MHz, respetively) s well s ierent sturtion powers. Figure shows the experimentl optil spetr o the pulse output (Fig.,) long with the temporl tres otine y seon-orer nonolliner utoorreltor (Fig.,) or the two systems (EYDFA in Fig., n EDFA in Fig.,) t our input powers to the ring resontor. The pulses visile in the utoorreltion trins hve temporl urtion tht ereses notiely s the input power inreses, s expete or typil pssive moeloking sheme. From these plots, it woul pper tht the lser se on the high-power EYDFA h superior overll perormne euse its pulsewith ws onsierly shorter. However, this ignores the t tht the utoorreltion mesurements verge over ny long-time sle lututions o the lser, without requiring stle pulse output. The key issue o lser stility or line oherene is etter illustrte nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.

3 nture ommunitions DOI:.38/nomms76 ARTICLE Cling Ring Bus Through A Dely line EDFA Isoltor Autoorreltor 7µm Input Drop Bn-pss Pol. ontroller OSA Ring OSA Osillosope Bus Ring-resontor Figure Filter-riven our-wve mixing esign. () Shemti o the entrl omponent monolithilly integrte 4-port high-q (Q =. million) miroring resontor (ire pigtils not shown) () High repetition rte lser se on ilter-riven FWM: the miroring resontor in () is emee in loop vity ontining gin ire (EDFA), n-pss ilter with the min purpose o ontrolling the entrl wvelength λ, ely line to ontrol the phse o the min vity moes with respet to the ring moes, n isoltor to ore the pulse-irulting iretion, n polriztion ontroller to t on the pulse polriztion, s the ring resontor is ireringent. The wveorm t the output o the mpliier is monitore with n utoorreltor to mesure the pulse urtion, n n optil spetrum nlyser (OSA) n photoioe onnete to n osillosope to respetively mesure the optil n rio requeny spetrum o the wveorm. An OSA is lso employe to monitor the optil spetrum t the output o the ring resontor. () SEM piture o the ring ross-setion eore epositing the upper ling o SiO. The wveguie ore is me o high inex (n =.7) ope sili glss. The sle r represents µm. () Eletri iel mol istriution or TM polrize em lulte through vetoril moe-solving. The sle r represents µm. y omprison etween the experimentl utoorreltion tres with the lulte tres (Fig.,, green plots) or ully stle n oherent system possessing the optil spetr in Fig.,. Wheres peret mth is oun or the short-length EDFA se, the long vity esign shows onsierly higher kgroun, thus lerly istinguishing unstle rom stle lser opertion. By hnging the mpliier riving urrent, we oserve minimum lsing threshol o 5 n 65 ma or the unstle n stle esigns, respetively (Fig. e,) tht orrespone to gin o ~ B or oth the ses. For the stle se, the input power in the ring versus the riving urrent is plotte in Fig.. To preserve the stle opertion, the ely line ws pte t the moe-loking threshol. This yiele slight hnge in totl losses tht inue kink in the plot roun urrent o 85 ma. The mximum input power in the ring ws 5.4 mw or the stle se, limite y the perormne o the EDFA. Disussion To etter quntiy the pulse-to-pulse mplitue stility o the two lsers we reore the eletril rio-requeny (RF) spetrum o the envelope signl, ollete t the output, using st photoetetor. Unstle osilltion (in the pulse mplitue) ws lwys oserve or the long vity esign or the EYDFA (Fig. 3,) or oth ontinuous wve (CW) n pulse regimes, owing to the presene o lrge numer o vity moes osillting in the ring resonne. In omplete ontrst to this, the short-vity onigurtion or the EDFA (Fig. 3 ) oul esily e stilize to give the very len result o Fig. 3e,, y simply justing the min vity length to entre n, ielly, single vity moe with respet to the ring resonne, therey ompletely eliminting ny min vity low-requeny eting. Severl stle osilltion onitions were oun through tuning the ely y over m. For the sme gin, the optil nwith (insets in Fig. 3,) or unstle lser opertion ws wier (tht is, leing to shorter output pulses) euse the instility resulte in strong mplitue moultion o the optil pulse trin in the min vity, thus inresing the sttistil pek power n enhning the nonliner intertions. This is ommon ourrene in moeloke lsers 9. Although we expet tht signiint externl temperture hnges woul eventully etune the externl vity length, one the therml stility ws rehe, stnr environmentl onitioning ( C) ws suiient to mintin peretly stle opertion within the time-rmework o our experimentl sessions (severl hours), highlighting the roustness o the stility onition. We onirme, y numeril simultions (Methos), the epenene o the stility on the reltive phse etween the min vity moes n the ring resontor moes (Fig. 4). We oun tht instility oul inee e either inue or suppresse simply y optimizing the phse o the min vity moes, tht is, the spetrl position o the min vity moes reltive to the ring resonnes. We onlue our experiments y hrterizing the phse noise 7,4,3 3. We oun tht ll o the emitte lines h nwith well elow 3 khz (ull-with t hl-mximum (FWHM)). This nwith hs een oun to e rmtilly inrese y the ontriution o the environmentl ousti noise tht we oul minimize ut not ully eliminte. Following the pproh o re. 4, we isriminte the linewith ssoite with the inherent nwith-quntum-limit, estimte to e elow 3 khz, whih suggests tht, ultimtely, proper pkging n ousti isoltion woul reue the optil spetrl linewith even urther. We lso investigte the soure timing jitter, tht is, the stohsti evition o the temporl pulse position in the trin. Following res. 7,3 3, we estimte rom the phse noise tht the jitter ontriution to the RF spetrl lines is < KHz. This is remrkle result or GHz moe-loke soure tht oes not use ny uxiliry stiliztion mehnisms. Our ultimte ojetive is verstile, ully monolithilly integrte lser soure. Beuse wveguie mpliiers hve een emonstrte in sili glss pltorms, we o not envisge ny unmentl issues preventing the ull integrtion o our sheme. This proo-o-onept evie represents key step in relizing ully integrte, stle, high perormne, lser soure operting t lexile n very high repetition rtes. In summry, we propose n emonstrte novel moe-loke lser se on monolithi high-q resontor, ple o generting nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.

4 nture ommunitions DOI:.38/nomms76 Power (B) e Power (mw) Wvelength (nm) 5 5,, 3, Current (ma) Autoorreltion (.u.) Power (B) , Current (ma) oth pioseon n su-pioseon trnsorm-limite pulses t repetition rte o.8 GHz n eyon. Our evie opertes vi new mehnism tht enles stle moe-loke lsing with negligile mplitue noise, n extrinsilly limite phse noise, not onstrine y the repetition rte. We elieve this work represents key milestone in the genertion o ultr-stle, high repetition rte, optil pulse soures, prtiulrly euse o its CMOS-omptile monolithi pltorm. Power (mw) Wvelength (nm) Figure Experimentl optil spetr n utoorreltion tres o the lser output or ierent FSRs o the min vity. (,) Long vity (FSR = 6. MHz) lser emission or inresing (top to ottom) pump powers, hieve through the use o long EYDFA, or 5.5 (lue), 8 (ornge), 4 (re) n 68 mw (lk) verge ring input powers. () shows the optil power spetrum mesure with the OSA n () gives the temporl wveorm o the lser mesure with the utoorreltor. Autoorreltion tres lulte strting rom the experimentl optil spetr or ully oherent n trnsorm-limite system re shown in green. These proiles re lulte y onsiering eh line o the experimentl optil spetr s eing peretly monohromti n inphse with the others, yieling n output pulse with FWHM o 73 s (uty yle ρ =.5) or the highest exittion power onition. The mesure utoorreltion shows onsierly higher kgroun (the pek-to-kgroun rtio is.5: or the 68 mw se) thn the expete utoorreltion (5:). (,) Short-vity lser emission using shortlength, low-power EDFA. () shows the optil power spetrum n () is the temporl wveorm o the lser output. Averge powers in the ring were s low s 8. (lue),.4 (ornge), 3. (re) n 5.4 mw (lk), with the min vity FSR = 68.5 MHz. Beuse o the lower vity energy hievle using the short-length EDFA, we show here mximum spetrl nwith limite to seven or eight lsing moes ssoite with the GHz FSR o the ring resontor. The utoorreltion tres expete rom the optil spetr or ully oherent trnsorm-limite system, shown in green, peretly mth the mesure tres, orresponing to trnsorm-limite pulse with (FWHM) o.3 ps (uty yle ρ =.46), with pek to kgroun rtio o 5: or the 5.4 mw se. In ll ses, the osilltion onition ws sel-strting n i not ritilly epen on the initil onitions. (e,) Averge input power in the ring versus the riving urrent or the EYDFA n the EDFA, respetively. Re irles inite multiwvelength osilltion. In the EDFA se, the ely line ws juste to keep the system in stle opertion or riving urrents >85 ma. Autoorreltion (.u.) Power (.u.) e ( B per iv) ( B per iv) (B per iv) Wvelength (nm) Wvelength (nm) Wvelength (nm).. Time (µs) Methos Simultions. The numeril simultions were perorme y solving the ouple equtions o the iel evolution (z,t) in the mpliying ire n o the iel (z,t) evolution in the nonliner ring nf F + + = tt z ( z, t) t ( z, t) i tt ( z, t) g( ) ( z, t) ( z, t) W nr R z( z, t) + t( z, t) + i tt( z, t) + ig ( z, t) ( z, t) = Here is the spee o light, n F, n R n β F, β R re the group inies n seonorer ispersion in the ire (F) n in the ring (R), respetively. Also, γ is the Kerr nonliner oeiient in the ring, wheres or the ire, α is the liner sorption n g( ) is the sturle gin expresse s L z g( ) = G exp ( z, t) P L with G n P representing the ire low-signl gin n the mpliier sturtion power, whih ontrols the energy in the lser vity, n L is the min vity length. We lso note tht Ω regultes the ire gin nwith. The equtions re solve in time with pseuo-spetrl metho n re ouple t the ring ports Frequeny (MHz) Figure 3 Lser RF noise. (,) Unstle osilltion onition or min vity FSR = 6 MHz, otine using the EYDFA (verge ring input power 68 mw). The inset in () shows the optil spetrum, s mesure with the OSA. In (), the RF signl lerly shows n irregulr pulstion. This is relete in the pperne o hrmonis in the RF spetrum () t 6 MHz intervls. The limite nwith o the RF spetrum is onsistent with the linewith (6 MHz) o eh ring resontor line. (,) Unstle osilltion onition or FSR = 68.5 MHz otine using the EDFA (multiple vity moes osillting per ilter resonne). In this onigurtion, the long timesle output shows omplex temporl ehviour, with the RF spetrum ontining peks orresponing to 68.5 MHz-spe hrmonis. The inset in () shows the optil spetrum, s mesure with the OSA. (e,) Stle osilltion onition or FSR = 67 MHz, orresponing to the se o one vity moe osillting per ilter resonne. The verge power in the ring ws 5.4 mw. The inset in (e) shows the optil spetrum. This regime is otine y justing the phse o the vity moes reltive to the ring resontor moes vi ree spe ely line. Power spetrl ensity (B per iv) () () nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.

5 nture ommunitions DOI:.38/nomms76 ARTICLE oring to the reltion out t out = r i r e RC F in t if ine MC where t n r re the trnsmission n reletion oeiients tht regulte the ring nwith, Φ MC ittes the position o the min vity moes with respet to the ring moes, n Φ RC ixes the position o the ring moes with respet to the entre o the gin nwith. The simultions were perorme or GHz repetition rte system, strting rom noise n letting the system reh the sttionry stte. The min vity is shorter when ompre with the experiment, to it the prolem within the 3 Gyte memory o our multiproessor system. The opertion is investigte or ring line FWHM RC = 3 GHz n min vity FSR MC = GHz. The rtio FWHM RC / FSR MC =.5 hs een hosen to mth the experimentl onitions. The ispersion is sle oringly to otin totl ispersion orresponing to the experiments. In Fig. 4-, the simultion results (output spetrum n mplitue) re plotte or growing mpliier sturtion energy (rom lue to lk), or Φ MC = (Fig. 4 ) n Φ MC =.875π (Fig. 4 ). The vity energy ets the stility s it regultes the numer o min vity moes tht osillte (Fig. 4,e). Conigurtions with lower energy n moes entre extly on ring resontor resonne (Φ MC = r) re typilly stle. The prmeter use in the experiments to istinguish the stle n unstle regimes is the nwith o the RF spetrum. In the numeris, it orrespons to the low-requeny omponents ( < GHz in the simultions) o the spetrum o the temporl power wveorm out (t). In Fig. 4g the FWHM o the RF spetrum versus Φ MC is shown or ierent mpliier sturtion powers. This quntity is expresse in units o min vity moes (opertively, the FWHM is ivie y the FSR o the min vity), tht is, FWHM RF = MC moes represents nwith s lrge s the FSR, n it orrespons to moerte unstle ehviour, or exmple, the re line in Fig. 4. As it is visile, in Fig. 4g, the stle operting rnge in terms o phse ely Φ MC shrinks with the vity energy. Devie. The wveguies use to rite the high-q ring resontors in our experiment possess high eetive nonlinerity ( W km ) ue to omintion o tight moe oninement n high intrinsi Kerr oeiient (n is ive times tht o sili glss). The ispersion is optimize or FWM in the C-n s it is smll n nomlous (~ ps m ) ner λ = 55 nm (re. 6), gurnteeing lrge FWM gin when pumpe in the C-Bn. Most signiintly, the wveguies exhiit very low liner ( <.4 B m ) n negligile nonliner optil loss (or exmple, two photon sorption) up to 5 GW m. All o these tors mke this pltorm prtiulrly ttrtive or low-power nonliner optis in the C-n,6 8. The input n output us wveguies o the resontor re pigtile to stnr single moe ire (SMF) using integrte moe onverters n V-groove tehnology, resulting in oupling losses o <.5 B per et. Set-up n experiments. The miroring resontor is emee in lrger ire loop vity, ontining n optil mpliier to provie gin, Fry isoltor, polriztion ontroller n ree spe ely line. A pssn ilter, with nwith lrge enough to pss ll o the osillting lines, is use to ontrol the entrl wvelength λ. The optil mpliiers use to perorm the experiments reporte here were either short-length EDFA, rom PriTel, or more onventionl (longer length) high-power erium-ytterium ope ire mpliier (EYDFA). The EYDFA h mximum sturtion output power o ~3 W, n proue min vity FSR o 6. MHz, orresponing to min vity ire length o 33 m, wheres the shortlength EDFA h sturtion output power o ~35 mw n resulte in vity length elow 3 m, orresponing to very lrge min vity FSR o 68.5 MHz. For the EYDFA-se lser, the npss ilter in the ire loop use to ontrol the entrl osillting wvelength ws 5-nm wie ilter with ~4 B loss. The ilter imposes gin ierene o ~.5 B etween the entrl n the irst sie moes. For the short-length lser, 5-nm wie ilter ws use inste, hrterize y loss o.5 B. We veriie tht the use o ierent ilters or eh lser h no impt on the perormnes in terms o overll stility or linewith the ilter nwith ws hosen to optimize the perormne o eh lser. For the EYDFA-se lser, muh higher pump powers were ville, so eresing the loss ws not s importnt s proviing wie-enough nwith to hieve the shortest possile pulsewith. For the short lser, limite gin ws ville n hene the low-loss, nrrow nwith ilter ws hosen; lso euse the overll output nwith ws muh smller thn the EYDFA lser owing to the lower ville vity energy. The entrl lsing wvelengths o the two lsers were juste to otin the mximum hievle nwith. The ierent optiml operting wvelength is minly relte to the ierent min vity ispersion (nomlous in oth ses) n ierent mpliier gin proiles. Amplitue noise hrteriztion. The lser mplitue noise ws etermine y mesuring the eletril RF spetrum o the lser using st photoetetor onnete to n mpliier (nwith, ~ MHz). (3) Spetrum (B per iv) Spetrum (B per iv) g FWHM RF (MC moes).. 5 Frequeny (THz) e Frequeny (THz) MC (r/π) Figure 4 Theoretil epenene o lser stility on mpliier sturtion energy n phse Φ MC o the min vity moes. In ll the plots, Φ RC = π (even numer o osillting ring resonnes). The lue, ornge, re n lk plots re or growing vity energy, respetively,,, 3 n 4 times the mpliier sturtion energy ssoite with the lue line. ( ) Lsing onition or Φ MC =. (,) Optil spetrum. () Temporl evolution, showing moulte peks in the unstle ses. ( ) Lsing onition or Φ MC =.875π. The plots (,e) show zoom on the entrl ring lines in (,), where the min vity moes re lerly istint (orresponing to only one line in the stle se). For lrger exittions, the numer o osillting min vity moes inreses. (g) RF nwith (FWHM) s untion o the min vity moes phse Φ MC, expresse in units o numer o min vity moes (or exmple, s the rtio etween the RF nwith n the min vity FSR). For the stle se (Fig. 3e), the RF signl exhiite ominnt omponent entre t the zero requeny (nmely iret urrent (DC) omponent), with nwith <.5 Hz (the resolution o our mesurement system) s well s n outo-n noise 55 B lower thn the DC pek. We estimte the rtio etween the power o the DC omponent n spetrl noise (within the MHz nwith) to e >4 B, gin limite y the sensitivity o the mesurement, whih in our se is itte y etetion n smpling noise. For the unstle se (Fig. 3), the RF nwith is very lrge n the DC omponent rings tully quite wek spetrl ontriution, the rtio lwys eing B. We estimte this to e ~ 3 B or the 6 MHz FSR min vity. Phse-noise hrteriztion. To hrterize the phse noise, we mesure the linewith o the osillting lines y irst seleting eh o them with nrrown ilter n then y nlysing the output using re-irulting elye sel-heteroyne intererometer (RDSHI) with ely line o 5.8 km, n moultion requeny o 6.5 MHz (res 7,4,3 3). As reporte in Fig. 5, we oun tht ll o the oservle emitte lines h nwith well elow 3 khz (FWHM), only limite y the environmentl ousti noise, tor tht we oul minimize ut not ompletely eliminte. This is onsistent with our est-it estimtion o the intrinsi Lorentzin ontriution to the linewith eing < 3 khz, tht is, the quntum limit or the linewith 4, n implies tht, ultimtely, proper pkging n ousti isoltion woul signiintly reue the RF spetrl linewiths. Notie tht the withs o the emission lines o the unstle esign were extly mthing the ring nwith, s lso onirme y the output mplitue spetrum. Although it is not possile to otin the pulse-jitter mplitue iretly rom the RF spetrum 3 owing to the extremely high repetition rte, the pulse jitter n e estimte rom the the optil spetrl roening w n o the RF lser lines 7,3 3. Uner the ssumption tht the phse n time jitter noises re white Power (.u.) Power (.u.) nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.

6 Power (B) Linewith FWHM (khz) Frequeny (MHz) Orer n unorrelte 3 the spetrl roening w jitter ue to the timing jitter is known to e proli oeiient o w n with respet to the entrl line: w n = w + w jitter (N N ) where N is generi moe numer, N is the moe numer orresponing to the minimum linewith, n w ounts or other phse noise ontriutions 7,3. As the resolution o our RDSHI mesurements ws < khz, we estimte pulse-jitter nwith w jitter < khz. Reerenes. Keller, U. Reent evelopments in ompt ultrst lsers. Nture 4, (3).. Hus, H. Moe-loking o lsers. IEEE J. Sel. Top. Qunt. 6, (). 3. Akhmeiev, N. N., Ankiewiz, A. & Soto-Crespo, J. Multisoliton solutions o the omplex Ginzurg-Lnu eqution. Phys. Rev. Lett. 79, (997). 4. Bulent, O. et l. Soliton similriton ire lser. Nture Photon. 4, 37 3 (). 5. Essimre, R. J., Krmer, G. & Winzer, P. J. Cpity limits o optil ire networks. J. Lightw. Tehnol. 8, 66 7 (). 6. Cotter, D. et l. Nonliner optis or high-spee igitl inormtion proessing. Siene 86, (999). 7. Hrusev, T. et l. Optil linewith o pssively moe-loke semionutor lser. Opt. Lett. 34, (9). 8. Jio, Z. J. et l. C-n InAs/InP quntum ot semionutor moe-loke lser emitting 43-GHz repetition rte pulses. IEEE Photon. Tehnol. Lett. 3, (). 9. Frno, P. et l. Sel-inue moultionl-instility lser. Opt. Lett., 9 (995).. Yoshi, E. & Nkzw, M. Low-threshol 5-GHz ontinuous-wve moultionl-instility erium-ope ire lser. Opt. Lett., 49 4 (997).. Quirog-Teixeiro, M. et l. Pssive moe loking y issiptive our-wve mixing. J. Opt. So. Am. B 5, 35 3 (998). Power (.u.) e Frequeny (khz) Figure 5 Phse noise mesurement perorme using re-irulting elye sel-heteroyne intererometer. Mesurements were perorme with ely line o 5.8 km, n moultion requeny o 6.5 MHz (res 7,4,3 3). The set-up mesurement is esrie in re. 3. () Bron view o the RDSHI photourrent power spetrum. The reirulting et notes re seprte y the moultion requeny o 6.5 MHz. ( e) RDSHI photourrent power spetr o the irst, seon, sixth n tenth et notes (lk), respetively, long with est it to the Voigt untion (re). The Voigt untion is eine s the onvolution o Gussin n Lorentzin untion (representing the extrinsi n intrinsi ontriution to the noise, respetively), s in re. 4. () Linewith FWHM (lk ots), Lorentzin (green ots) n Gussin (re ots) ontriutions o the Voigt est it untion versus the orer o the et note. From this mesurement, it is ler tht the Lorentzin ontriution (tht is, the quntum limit or the linewith) sturtes to vlue well elow 3 khz, wheres the Gussin ontriution is ominnt or the lrgest orer, initing tht the noise is ominte y extrinsi/environmentl ontriutions nture ommunitions DOI:.38/nomms76. Sylvestre, T. et l. Sel-inue moultionl instility lser revisite: norml ispersion n rk-pulse trin genertion. Opt. Lett. 7, (). 3. Shröer, J., Vo, T. D. & Eggleton, B. Repetition-rte-seletive, wvelengthtunle moe-loke lser t up to 64 GHz. Opt. Lett. 34, (9). 4. Shröer, J. et l. Dynmis o n ultrhigh-repetition-rte pssively moeloke Rmn ire lser. J. Opt. So. Am. B 5, (8). 5. Zhng, S. et l. Pssive moe loking t hrmonis o the ree spetrl rnge o the intrvity ilter in ire ring lser. Opt. Lett. 3, (5). 6. Kippenerg, T. J., Holzwrth, R. & Dims, S. A. Miroresontor-se optil requeny oms. Siene 33, (). 7. Del Hye, P., Arizet, O., Shliesser, A., Holzwrth, R. & Kippenerg, T. J. Full stiliztion o miroresontor-se optil requeny om. Phys. Rev. Lett., 5393 (8). 8. Del Hye, P. et l. Optil requeny om genertion rom monolithi miroresontor. Nture 45, 4 7 (7). 9. Gruinin, I. S., Yu, N. & Mleki, L. Genertion o optil requeny oms with CF resontor. Opt. Lett. 34, (9).. Levy, J. S. et l. CMOS-omptile multiple-wvelength osilltor or on-hip optil interonnets. Nture Photon. 4, 37 4 ().. Rzzri, L. et l. CMOS-omptile integrte optil hyper-prmetri osilltor. Nture Photon. 4, 4 45 ().. Ferous, F. et l. Spetrl line-y-line pulse shping o on-hip miroresontor requeny oms. Nture Photon. 5, (). 3. Shwlow, A. L. & Townes, C. H. Inrre n optil msers. Phys. Rev., (958). 4. Yoshi, M., Ono, A. & Nkzw, M. GHz regenertively moeloke semionutor optil mpliier ire ring lser n its linewith hrteristis. Opt. Lett. 3, (7). 5. Crmon, T., Yng, L. & Vhl, K. Dynmil therml ehvior n therml sel-stility o mirovities. Opt. Express, (4). 6. Ferrer, M. et l. Low power our wve mixing in n integrte, miro-ring resontor with Q=. million. Opt. Express 7, (9). 7. Ferrer, M. et l. Low-power ontinuous-wve nonliner optis in ope sili glss integrte wveguie strutures. Nture Photon., (8). 8. Psquzi, A. et l. Su-pioseon phse-sensitive optil pulse hrteriztion on hip. Nture Photon. 5, (). 9. Houh, A., Lelon, H., Slhi, M., Komrov, A. & Snhez, F. Anlysis o soliton pttern ormtion in pssively moe-loke ire lsers. Phys. Rev. A 78, 4386 (8). 3. Dwson, J. W., Prk, N. & Vhl, K. J. An improve elye sel-heteroyne intererometer or linewith mesurements. IEEE Photon. Tehnol. Lett. 4, (99). 3. Line, D. Chrteriztion o the noise in ontinuously operting moe-loke lsers. Appl. Phys. B 39, 7 (986). 3. Hus, H. A. & Meozzi, A. Noise o moe-loke lsers. IEEE J. Quntum Eletron. 9, (993). Aknowlegements This work ws supporte y the Cnin FQRNT n NSERC, n the Austrlin Reserh Counil (ARC) Centres o Exellene n Disovery Projets progrms. M.P. knowleges the support o the Mrie Curie People projet TOBIAS PIOF- GA-8-6. We lso knowlege support rom QPS Photonis, Enlne n MPB Communitions. Finlly, we thnk Steno Trillo or the isussions on the theoretil sis o nonliner issiptive systems n Tuor Johnston or ritil revision o the mnusript. Author ontriutions M.P. n A.P. esigne the lser operting sheme n priniple o opertion. M.P. n A.P. esigne the short-length mpliier use in the stle lser esign. M.P., A.P. n Y.P. uilt the lser prototype use in the pper s proo o onept. A.P. evelope the theoretil n numeril nlyses. S.T.C. n B.E.L. esigne n rite the resontor exploite in the lser esign. D.J.M. n R.M. supervise the projet. M.P., A.P., D.M. n R.M. wrote the mnusript. Aitionl inormtion Competing innil interests: The uthors elre no ompeting innil interests. Reprints n permission inormtion is ville online t reprintsnpermissions/ How to ite this rtile: Peinti, M. et l. Demonstrtion o stle ultrst lser se on nonliner mirovity. Nt. Commun. 3:765 oi:.38/nomms76 (). Liense: This work is liense uner Cretive Commons Attriution-NonCommeril- Shre Alike 3. Unporte Liense. To view opy o this liense, visit retiveommons.org/lienses/y-n-s/3./ nture ommunitions 3:765 DOI:.38/nomms76 Mmilln Pulishers Limite. All rights reserve.