Development of a compact Yb optical lattice clock

Development of a compact Yb optical lattice clock A. A. Görlitz, C. Abou-Jaoudeh, C. Bruni, B. I. Ernsting, A. Nevsky, S. Schiller C. ESA Workshop on Optical Atomic Clocks D. Frascati, 14 th 16 th of October 2009 Space Optical Clocks (SOC)

Ytterbium Bosons: 168 Yb, 170 Yb, 172 Yb, 174 Yb, 176 Yb Fermions: 171 Yb, 173 Yb blue MOT (399 nm) green MOT (556 nm)

Content Laser cooling of Yb Compact source of ultracold Yb Setup for a 3D optical lattice Compact clock laser for Yb Outlook

Laser cooling of Yb Standard cooling scheme Zeeman slower

Laser cooling of Yb Standard cooling scheme Zeeman slower Precooling MOT

Laser cooling of Yb Standard cooling scheme Zeeman slower Precooling MOT Postcooling MOT required: ~ 10 7 atoms ~ 10 11 cm -3 < 50 µk

Laser cooling of Yb Standard cooling scheme Zeeman slower Precooling MOT Postcooling MOT Optical trap/lattice

Laser cooling of Yb Standard (pre/post)cooling scheme Direct loading of postcooling MOT

Laser cooling of Yb Standard (pre/post)cooling scheme Direct loading of postcooling MOT Atom number: ~ 3-4x10 7 Atom number: ~ 2-3x10 7 Density: ~ 10 9 cm -3 Loading time: ~ 50 300 ms Temperature: 1 5 mk (lower for fermions at low atom number) Density: ~ 10 11 cm -3 Loading time: ~ 3-10 s Temperature: ~ 500 µk ( 174 Yb), 100 µk ( 171 Yb) µk postcooling necessary

Laser cooling of Yb Standard (pre/post)cooling scheme Direct loading of postcooling MOT Atom number: ~ 2-3x10 7 Atom number: ~ 2-3x10 7 Density: ~ 10 11 cm -3 Loading time: ~ 100 350 ms Temperature: ~ 50 µk Density: ~ 10 11 cm -3 Loading time: ~ 3-10 s Temperature: ~ 500 µk ( 174 Yb), 100 µk ( 171 Yb) µk parameter change (detuning, intensity)

Laser cooling of Yb Old stationary apparatus on 2 optical tables blue MOT: frequency-doubled Ti:Sapphire green green MOT: dye Laser pump laser

Compact source of ultracold Yb New compact apparatus 1 movable optical table (~ 2 m 2 ) compactified vacuum system optimized for optical access and implementation of optical lattice all laser systems diode based Green laser (556 nm) Blue laser system (399 nm) Lattice laser (759 nm) Vacuum chamber

Compact source of ultracold Yb spectroscopy beam Yb oven Zeeman slower Main chamber

Compact source of ultracold Yb Blue diode-laser system @ 399 nm Master: ECDL (12 mw) Slave: injection-seeded (> 30 mw) usable power: slower: ~ 5 mw MOT: > 15 mw

Compact source of ultracold Yb Blue diode-laser system @ 399 nm laser diode Master: ECDL (12 mw) collimating lens diffraction grating

Compact source of ultracold Yb Blue Yb MOT up to 10 7 atoms 171 Yb, 172 Yb, 173 Yb, 174 Yb, 176 Yb trapped loading time: < 300 ms MOT beams (399 nm) Zeeman slower beam (399 nm)

Compact source of ultracold Yb Green laser system @ 556 nm: diode laser at 1112 nm (> 100 mw in grating setup), prestabilized to Fabry-Perot single-pass frequency doubling in PPLN waveguide ( up to 11 mw @ 556 nm)

Compact source of ultracold Yb Frequency doubling in PPLN waveguide: 556 nm 1112 nm diode laser collimating lense temperature-stabilized oven PPLN crystal with 21 waveguides (L = 2 cm)

Compact source of ultracold Yb Frequency doubling in PPLN waveguide: 0.5 mm ~2 µm ~3-5 µm 20 mm Total: 3 mm HCPhotonics HCPhotonics

Compact source of ultracold Yb Frequency doubling in PPLN waveguide: 75 mw @ 1112 nm before crystal 30 mw inside crystal (37% coupling efficiency) 11 mw @ 556 nm (efficiency~ 300%/(W cm 2 )) Specified efficiency: > 150%/(W cm 2 )

Compact source of ultracold Yb Green MOT: First green MOT in transportable chamber realized this week!

Compact source of ultracold Yb Green laser alternative: frequency-doubled fiber laser: 1 W @ 1112 nm ~ 10 khz linewidth 30 mw @ 556 nm 30 mw @ 556 nm (single-pass in PPLN crystal)

Setup for a 3D optical lattice magic wavelength for Yb: 759 nm 3D for bosonic Yb (i.e. 174 Yb) 1D for all isotopes

Setup for a 3D optical lattice Laser system @ 759 nm: self-injected tapered laser morethan 500 mw tapered laser optical grating

Setup for a 3D optical lattice Laser system @ 760 nm: self-injected tapered laser morethan 500 mw

Setup for a 3D optical lattice Laser system @ 760 nm: self-injected tapered laser morethan 500 mw linewidth < 3 MHz

Setup for a 3D optical lattice Design criteria: compact setup large volume ( > 100 µm) sufficient trap depth (U ~ 100 µk)

Setup for a 3D optical lattice Solution: linear resonator insideid vacuum apparatus beam waist: 150 µm finesse ~ 300 P in x 100 ~ 30 W trap depth ~ 80 µk

Setup for a 3D optical lattice Solution: folded linear resonator insideid vacuum apparatus beam waist: 150 µm finesse ~ 300 P in x 100 ~ 30 W trap depth ~ 80 µk

Compact clock laser for Yb A diode-laser based source @ 578 nm Motivation: Development of a simple and compact clock laser for Yb Novel laser (InAs/GaAs/InGaAs) diodes manufactured by Innolume (Dortumund, D) Frequency range: 1.064 132µm 1.32 µm, in quantum-dot and quantum-well technology Laser chips operated in ECDL configuration Output power: up to 80 mw, Tunable over many tens of nm Problem for high-bandwidth frequency locking: current modulation exhibits a large phase shift Our solution at present: intra-cavity EOM InAs quantum dots (AFM image)

Compact clock laser for Yb First demonstration of a narrow-linewidth QD-ECDL Diffraction grating Aspheric lens Aspheric lens Aspheric lens Aspheric lens QD laser Diffraction grating QD laser A. Nevsky et al., Appl. Phys. B 92, 501-507 (2008). SHG: PPLN waveguide, 200 µw @ 578 nm for 12 mw @ 1156 nm

Compact clock laser for Yb Goal: 1 Hz clock laser linewidth & 10-15 frequency instability ULE-Cavity: finesse 330 000, 4.5 khz linewidth zero thermal expansion coefficient at 20 C dual layer temperature stabilization T = 2 x 10-4 K @ 1min 5 x 10-5 K @ 10 h active vibration stabilization

Compact clock laser for Yb AOM EOM Fiber for 1156 nm (frequency measurement) Fiber for 578 nm (spectroscopy) Fiber incoupler for PPLN waveguide ULE cavity IR camera Place for 578 nm fiber stabilization SHG in PPLN waveguide ECDL1156nm 90 cm

Compact clock laser for Yb Overview Lock ECQDL 1156 nm Breadboard 1 O I PPLN waveguide 578 nm ULE high-finesse cavity AOM + - EOM-1 f m =10.2 MHz Optical fiber 5 m AVI-1 Breadboard 2 FFT analyzer Frequency counter RF signal from the AOM + - Lock ULE high-finesse cavity EOM-2 f m =12.3 MHz AOM AVI-2

Compact clock laser for Yb ULE 2 ULE 1 AVI

Compact clock laser for Yb Beat linewidths 1.0 Averaging 1 s FFT resolution 1 Hz 1.0 Averaging 100 s FFT resolution 1 Hz itude (a.u.) 0.5 FWHM 2.8 Hz itude (a.u.) 0.5 FWHM 40 Hz ampli ampli 00 0.0 00 0.0 0 100 200 300 400 0 100 200 300 400 frequency [Hz] frequency [Hz] No drift subtraction

Compact clock laser for Yb Frequency stability RAV of the beat signal between two ULE resonators (drift removed) Absolute frequency measurement of the ULE resonator (using frequency comb and GPS/H-maser) RAV 10-14 - f 0 [khz] Frequency - 200 150 100 50 [Hz] [Hz] Linear Fit of data_freq1 Linear drift 56 mhz/s 10-15 0 f 0 = 259.147.918.727.124 Hz 1 10 100 integration time [s] 0 7 14 21 28 35 time [d] Light will be transported over 350 m Light will be transported over 350 m fiber to Yb apparatus Fiber stabilization already tested

Compact clock laser for Yb Complete system Frequency metrology laboratory (HHUD-I) ECDL locked to ULE cavity Trapped cold Ytterbium lab SHG 350 m intra-building optical fiber GPS Ti:Sapphire Frequency comb Active hydrogen maser

Tools: frequency metrology Frequency measurements w.r.t. GPS-delivered time, via H-maser Performance of comb was tested using a cryogenic optical resonator GPS σ rel (τ) 10-12 10-13 Cryogenic sapphire-resonator demo demo demo demo demo H-maser (specification) demo demo demo demo demo demo demo demo demo demo demo demo demo demo demo Laser stabilized to 3 K resonator Ti:Sa comb Mas- er 10-14 demo demo demo demo demo demo demo demo demo demo mean optical frequency f cw = 281 623 818 264 252 Hz 1 10 100 1000 Averaging time [s] Next generation of cryogenic optical resonators, might be useful for stability evaluation Need to eventually move optical clock system to a national metrology institute!

Tools: laser comparison Virtual beat method: I(f) 1 G. Grosche et al., Eur. Phys. J. D 48,, 27 (2008) 2 f ceo f rep m 1 m 2 f Laser 1 DDS Synthesizer Laser 2 m virtual beat = ( 1 + f ceo ) 1 ( 2 + f ceo ) f Laser1 = m 1 f rep + f ceo - m 2 1 m 1 m 2 f Laser2 = m 2 f rep + f ceo - 2 virtual beat = f laser1 - f laser2

Tools: laser comparison Test measurement of virtual beat [dbm] n 1 Hz BW Power i -20-30 -40-50 -60-70 -80-90 -100 Virtual beat between fundamental @ 1064 nm and 2 nd harmonic @ 532 nm Averaging: 20 span: 100 Hz, RBW = 1 Hz span: 1 khz, RBW = 9,1 Hz span: 10 khz, RBW = 91 Hz span: 100 khz, RBW = 910 Hz span: 1 MHz, RBW = 9100 Hz span: 10 MHz, RBW = 91000 khz -30-40 -50-60 -70-80 -90 FWHM = 2 Hz -5-4 -3-2 -1 0 1 2 3 4 5 Frequency - x c [khz] -110 f -120 c = 38,1749463 MHz -5-4 -3-2 -1 0 1 2 3 4 5 Frequency - x c [MHz]

Summary MOTs realized in compact clock apparatus Optical lattice setup developed Narrow linewidth clock laser developed Tools for frequency measurement ready Thanks for their help to: F. Baumer, N. Nemitz, R. Stephan, U. Bressel, A. Wicht, M. Okhapkin, D. Iwaschko!

Atomic mixtures with Yb Hybrid trap for Yb-Rb mixtures Yb: E dipole trap for Yb magnetic trap for Rb Rb: offset coil T Yb = TRb rf for evaporative cooling of Rb pinch coil clover leaves evaporate Rb sympathetically cool Yb two-component quantum gas starting point for molecules

Sympathetic cooling 172 Yb Thermalization rate strongly isotope-dependent

Phase separation of Yb and Rb T~ 2 µk increasing Rb density

Thanks for your attention!