1. Introduction. 2. New approaches

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1 New Approaches To An Indium Ion Optical Frequency Standard Kazuhiro HAYASAKA National Institute of Information and Communications Technology(NICT) ECTI200

2 . Introduction Outline 2. New approaches. Status of the project (0)In + -Ca + chain synthesis ()quantum logic spectroscopy (2)VUV excitation () S 0 - P excitation 4.Summary ECTI200 2

3 Motivation: smaller frequency uncertainty 40 Ca + optical clock at NICT st system: no magnetic shield 2 P /2 97nm 866nm 40 Ca + 2 D 5/ (7) Hz (2 0-4 ) Appl. Phys. Expr., 0670(2008) 2 D /2 729nm (4THz) (.0) Hz Innsbruck, PRL.02, (2009) 2 S /2 clock pulse duration 4ms 2 nd system: with magnetic shield However, fractional uncertainty is limited to in the order of 0-5 due to quadrupole shift, black body radiation(bbr) shift ECTI200 clock pulse duration 20ms need of IIIA ions (B +, Al +, Ga +, In +, Th + ) for smaller fractional uncertainty

4 Energy structure of IIIA ions Common feature of III A ions good clock transition ( S 0 - P 0 ) high Q value no quadrupole shift small BBR shift cooling/detection transition ( S 0 - P ) in VUV hard to access 27 Al + (NIST) 5 In + (MPQ, Erlangen) P I=7/2 P I=9/2 Quantum logic spectroscopy (QLS) recorded the smallest uncertainty of Phys. Rev. Lett. 04, (200) ECTI200 l= 67 nm G=.5 GHz cooling detection S 0 P 2 267nm 5Hz P clock l=267 nm t=2 s 8mHz l= 59nm G=. GHz cooling detection S 0 P 2 20nm 60kHz P P 0 clock l=27 nm t=0.20 s 0.8Hz S 0 - P transition can supply cooling and detection 4

5 Traditional In + optical clock (MPQ, Erlangen) P Single In + in a Paul-Straubel trap - bicromatic sideband cooling at 20nm S 0 P 2 20nm 60kHz P P 0 clock l=27 nm t=0.20 s 0.8Hz clock transition ( S 0 - P 0 ) - linewidth 0.8Hz - no quadrupole shift - small BBR shift estimated at 00K < Becker et.al. PRA 6,05802(200) Peik (2002) Wang et. al. (2006) Kajita (200) Fractional uncertainty in the order of 0-8 is expected However, reported numbers remain in the order of (0.2) khz ( ) von Zanthier et. al. Opt. Lett. 25, 526(2000) (0.256) khz ( ) Y.H Wang, et. al. Opt. Commun. 27, 526(2007) ECTI200 5

6 New approaches Basic configuration: In + in a linear trap with other ions ECTI200 Cooling is provided by sympathetic cooling (currently by 40 Ca +, in future by 5 Cd + ) Detection is provided by three methods. Quantum logic spectroscopy (QLS) 2. Vacuum ultraviolet (VUV) excitation at 59nm multimode pulses generated by high harmonic generation(hhg) of Ti:S laser (795nm) might be used.. S 0 - P excitation at 20nm slow detection is compensated by clock laser locked to Sr optical lattice clock. P l= 59nm G=. GHz cooling detection S 0 P 2 20nm 60kHz I=9/2 P P 0 clock l=27 nm t=0.20 s 0.8Hz 6

7 Procedure of building Ca + - In + chains. prepare a Ca + chain Target example: Ca+ In + Ca + 2. load In + by resonant photo-ionization. reduce number of In + by rf-kick 4. adjust position of In + by axial potential adjustment ECTI200 7

8 linear trap r 0 =.8mm 2 z 0 = 8mm W/2p = 2.6MHz, w/2p=0.82mhz DC -00V Experimental setup rf control DC control Ca oven In oven image-intensified CCD camera magnification ~20 z In + is NOT visible 00ms integration time ECTI200 8

9 Snapshot of Ca+-In+ chain synthesis Ca+ number adjustment by rf control In+ number adjustment by rf control wr = ev0 µ 2mr02 W 0 m w r (5 In + ) = 0.5 wr ( 40 Ca + ) rf voltage 40V->60V s V0=98V sec wr(ca+)/2p=77khz wr(in+)/2p=62khz Configuration control by DC control Loading of In+ by resonant photo-ionizaiton 2D (autoionizing) DC electrode voltage 0->22V 4nm 2S /2 4nm 2P ECTI 200 Ca+ /2 2P /2 In+ 9

10 Identification of In + vibrational frequencies depend on mass identification of the mass possible configuration w z ( mixed) / w ( Ca (of the lowest mode) 40 Ca In G. Morigi, et al, Euro. Phys. J. D, 26(200) z + ) frequency on DC electrode 2 40 Ca Ca X + excitation voltage 0.kHz 75.9kHz 77.8kHz ECTI 200 X + = 5 In + is identified 0

11 Quantum logic spectroscopy Collaboration with Prof. Urabe group at Osaka univ. 5 In + 40 Ca + P l= 59nm G=. GHz S 0 P 2 P P 0 clock 27nm 0.8Hz 2 P /2 detection 97nm 20MHz 2 S /2 2 D 5/2 mj=5/2 qubit 729nm 0.2Hz mj=/2 In + + Ca + chain is generated with high reproducibility 0 s 50mm sideband cooling (729nm) to the ground state is in progress ECTI200

12 Coherent VUV source for optical clocks P Common level structure of atomic clocks Strong transiton cooling & detection P 2 P P 0 Clock transition S 0 Clock scheme Sr Al + In + Th Lattice clock Quantum logic spectroscopy Single ion?? Clock transition S 0 - P 0 S 0 - P 0 S 0 - P 0 Nuclear transition l of clock transition (nm) ± l of S 0 - P transition (nm) All within 5 th harmonic of Ti:S! Our target

13 VUV generation Setup DPSS laser (7W, 52nm, CW) Mode-locked Ti:S oscillator (~700mW, 795nm, 65fs) Pulse compressor (SF0 prism pair) Feedback to PZT to lock frep (2MHz) Vacuum Chamber Hänsch-Couillaud locking 99.68% Input coupler Roundtrip length: 2.7m Vacuum: <e-5 torr Curvature mirror: 00mm average intracavity power: 250W peak intensity: 0 W/cm 2 Xe gas jet Fluorescent plate Grating mirror

14 Observation of the VUV output Xe gas jet Grating mirror 2nd order st order H H7 H5 Fluorescent plate stable output is maintained over minute even with manual adjustment of fceo power[mw] first measurement of 5th high harmonic (59nm) with a phototube:.5mw ( modes total) time[s]

15 Estimation of photon counting rate In + P F=7/2 F=9/2 F=/2 645MHz 759MHz items high harmonic average power Repetition rate value 00mW* 0MHz 59nm Three HFS levels are simultaneously excited by 5 th HH of the 0MHz comb Number of comb teeth S 0 - P linewidth 77MHz Focus diameter mm Detection solid angle Detector efficiency 40% S 0 HFS splitting calculated from P. Jonsson, Martin Andersson J. Phys. B: (2007) single In + photon counting rate: 2,000 cps *Fiber laser based system at JILA: 50uW at 5nm (7 th )!!

16 Stabilization of In + -Ca + configuration a (Ca +,In +,Ca + ) n 0 =00.5kHz AM applied to Ca + laser (97nm) 98.5kHz 00.5kHz b (In +,Ca +,Ca + ) n 0 =98.5kHz 20s c (Ca +,Ca +,In + ) n 0 =98.5kHz configuration-selective destabilization is possible 200s AM (98.5kHz) upon finding unwanted config. simple way to keep In + -Ca + configuration ECTI200 6

17 diode--laser based 20nm source diode 5In+ P l= 59nm G=. GHz S 0 ECTI200 20nm 60kHz P 2 P P 0 clock 27nm 0.8Hz 5mW is expected for 00mW input from MOPA at 922nm optical feedback ECDL (922nm) PPKTP cavity 46nm 40mW 922nm 80mW QPM (40.6±0. C) BBO cavity 20nm 2.0mW Critical phase matching (q=60,φ=0 ) 7

18 PD Clock laser under construction Vacuum Chamber ULE Cavity Servo λ/4 DBM PD 5MHz M Master ECDL 25 mw Toptica LD AR Isolator ~900mW After fiber ~00mW M2K Tapered Amp. PBS To optical comb EOM Single Mode Fiber (2m) PPKTP Ricol x x 0mm AR coating at 946nm+47nm M Super BBO Casix x x 0mm AR coating at 47nm+27nm To ion trap chamber >>mw Vibration-insensitive Cubic ULE cavity designed finesse 250,000 Relative stability of 0-5 at s is expected

19 Hybrid optical clock servo In + In+ clock laser optical comb Sr optical clock servo A clock with stability of optical lattice clock and accuracy of single ion clock ECTI200 9

20 Summary New approaches to In + an optical frequency standard Sympathetically cooled In + in a linear trap Detection by three methods Quantum logic spectroscopy Initialization of In + -Ca + is in progress VUV excitation.5mw at 59 nm was generated 2,000cps expected when 00mW is available S 0 - P excitation assisted by Sr optical clock all components are almost ready Clock operation will be reported in the 2 nd ECTI conference ECTI200 20