Progress towards laser cooling strontium atoms on the intercombination transition

Progress towards laser cooling strontium atoms on the

intercombination transition

Danielle BoddyDurham University – Atomic & Molecular Physics group

The team

Progress towards laser cooling strontium atoms on the intercombination transition - May 2011

Motivation: Rydberg physics Ionization

threshold

States of high principal quantum number n.

Exaggerated size and lifetimes.

Can be prepared through laser excitation.

Greatly enhanced inter-atomic interactions.

Strong, tunable, long-range dipole-dipole

interactions among the atoms.

Applications include quantum computation. M. Saffman et. al., Rev. Mod. Phys. 82, 2313 (2010)

Motivation: Dipole blockade

Y Miroshnychenko et al., Nat. Phys. 5, 115-118 (2009)E Urban et al., Nat. Phys. 5, 110-114 (2009)

Sr88 is an alkaline earth metal with no hyperfinestructure.

Two valence electrons permits two electron excitation.

Motivation: An introduction to strontium

Ground state

Rydberg state

Doubly excited state

Two-electron excitation of an interacting cold Rydberg gas J. Millen, G. Lochead and M. P. A. Jones Phys. Rev. Lett. 105, 213004 (2010)

Spectroscopy of strontium Rydberg states using electromagnetically induced transparency S. Mauger, J. Millen and M. P. A. Jones J. Phys. B: At. Mol. Opt Phys. 40, F319 (2007)

At present, we’re investigating the spatial excited state distribution.

Motivation: Dipole blockade regime

T ~ 5 mKDensity ~ 1 x 109 cm-3

T ~ 400 nKDensity ~ 1 x 1012 cm-3

No blockade

How do we enter the dipole blockade regime?

Blockaded

Motivation: Laser cooling of strontium

λ = 689 nmΓ = 2π x 7.5 kHz2nd stage cooling

λ = 461 nmΓ = 2π x 32

MHz1st stage cooling

1S0 → 3P1 intercombination transition → TD ≈ 180 nK.

Photon recoil limits TD → Tmin ≈ 460 nK.

Introduce two stages of cooling:

First cool on the (5s2) 1S0 → (5s5p) 1P1.

Second cool on the narrow-line (5s2) 1S0 → (5s5p) 3P1 .

Outline

Simple laser stabilization set-up

Laser system

Pound-Drever-Hall (PDH)

Locking to an atomic transition

Fluorescence

Electron shelving

Summary

Laser system

Fabry-Perot

cavity

Atomic signal

Red MOT

Laser system

Fabry-Perot

cavity

Atomic signal

Red MOT

Laser system

Compared old and new designs.

Laser system

frequency

NEW2 Wavemeter

Wavemeter1

frequency2

Laser system

Old New

New design fluctuates more in the short term.Little difference between the long term stability.

Laser system

Fabry-Perot

cavity

Atomic signal

Red MOT

Fabry-Perot

cavity

Pound-Drever-Hall (PDH) technique

Require the laser linewidth < 7.5 kHz.

Noise broadens the linewidth to the MHz regime.

Uses Fabry-Perot cavity as a frequency reference.

Cavity peaks are spaced by the free spectral range :

Phase modulator adds sidebands to the laser.

High-finesse Fabry-Perot cavity measures the time-varying frequency of the laser input.

An electronic feedback loop works to correct the frequency error and maintain constant optical power.

Phase modulato

Lock Box

Etalon4

PiezoCurrent

modulation

Theory: See E. Black., Am. J. Phys. 69 (1) 79 (2001)

Slow feedback to

Fast feedback to

Feedback to cavity piezo

Atomic signal

Lock Box

A crystal oscillator phase modulates the 689 nm beam at a frequency of 10 MHz.

Laser locks to the central feature of the PDH error signal

Increasing the gradient of the error signal strengthens the lock and reduces the linewidth.

(a) (b) (c) (d)

Gradient depends on sideband power: carrier power ratio.

Gradient steepest when Ps = 0.42 Pc

Theory: See E. Black., Am. J. Phys. 69 (1) 79 (2001)

Pound-Drever-Hall (PDH) summary

Generate PDH signal

Gradient of error signal → strength of lock and laser linewidth

NEXT STEP: Finish high bandwidth servo

IMPROVEMENTS: Build high-finesse cavity

Laser system

Fabry-Perot

cavity

Atomic signal

Red MOT

Atomic signal

Locking to an atomic transition

CHALLENGE: Detecting the transition.

Two detection methods:

1. Electron Shelving

2. Fluorescence

Electron shelving

Excite atoms to the 3P1 and measure the rate at which these atoms decay out of the state.

Photon scattering rate is proportional to the linewidth of the transition.

λ = 689 nm

λ = 461 nm

Electron shelving

λ = 461 nm

atomic beam

photodiode

The amount of scattered light is proportional to the

number of atoms initially in the 1S0 ground state.

Electron shelving

λ = 689 nm

λ = 461 nm

atomic beam

photodiode

Electron shelving: Experiment

atomic beam

photodiode

atomic beam

photodiode

atomic beam

photodiode

≈ 32 MHz

Electron shelving: Lifetime measurement

Using a velocity of 500 ms-1

Lifetime of 3P1 is (23 ± 1) μs

Gradient: (8.9 ± 0.2) x 10-2 mm-1

Electron shelving: Crossed beams

atomic beam

photodiode

FWHM crossed beams is ≈ 20 MHz.Linewidth has reduced by 1/3.

This is not narrow enough for the Fabry-Perot to lock to!

Electron shelving: Summary

Detected the transition indirectly via electron shelving.

Determined the lifetime of the 3P1 state.

And the lineshape?

Tried crossing the beams:

Did the linewidth reduce? Is this narrow enough for the laser to lock to?

Work in progress

Try a direct method of detection.

Fluorescence: The experiment

Strontium has negligible vapour pressure at room temperature → heated to 900 K.

atomic beam

CCD camera takes spatially resolved images of the fluorescence.

Exposure length set to 65.5 ms.

(a) Slice along direction of laser beam → absorption and decay.

(b) Slice along direction of atomic

beam → transverse velocity distribution.

(b)(a)

Gradient: (9.0 ± 0.3) x 10-2 mm-1

Using a velocity of 500 ms-1

Lifetime of 3P1 is (22.2 ± 0.7) μs

Other time resolved fluorescence detection: τ = (21.3 ± 0.5) μs See R Drozdowski., Phys. D. 41:125 (1997)

BUT what about the absorption?

Fluorescence: The model

Solves optical bloch equations (OBEs) for a two level atom as a function of

distance.

Velocity distribution of atoms α Tk

Bev 23

Randomly selects a value of and .

If the value of is kept.

)(vf 'v

)'()( vfvf 'v

Assuming the laser is on resonance the only other unknown in the OBEs is

the Rabi frequency.

Top hat pulse: Ed.

Gaussian pulse: 2

2)(2. waistwaistx

0 .0 002 0 .0 004 0 .0 006 0 .00 08 0 .0 010 0 .00 12D istan cem0 .2

E xci ted po pu lat io n state 22

Top hat pulse Gaussian pulse

Velocity of 500 ms-1

0 .00 1 0 .00 2 0 .0 03 0 .00 4 0 .00 5 0 .0 06D is tancem0 .1

E xcited pop u lat ion state 22

0 .001 0 .0 02 0 .003 0 .00 4 0 .00 5 0 .00 6D is tancem0 .2

E xcited po pu latio n state 22

2 x waist

Fluorescence: Summary

Detected the transition directly.

Determined the lifetime of the 3P1 state.

Written code to model absorption and decay.

Data and theory don’t quite agree.

NEXT: Try locking to this fluorescence signal.

Need to find source of problem.

Summary

689 nm laser built and tested.

Need to finish PDH high bandwidth servo circuit.

Build high-finesse cavity.

Tested an indirect and direct method to detect the transition.

Measured lifetime of 3P1 state from both methods.

Try locking to fluorescence signal.

If this works….GREAT!

If it doesn’t work….try pump-probe spectroscopy

Red MOT → colder atoms

Questions?

Thanks for listening Any questions?

Progress towards laser cooling strontium atoms on the intercombination transition

Documents

Winter 2015 | jila.colorado.edu Winter 2015 …...Atomic & Molecular Physics Strontium atoms in a quantum simulator display SU(N ≤ 10) symmetry because of having 10 different nuclear

Spectroscopic analysis of solid oxide fuel cell material with XPS · 2018. 12. 28. · of strontium carbonate relative to the concentration of lattice- bound strontium atoms. These

Laser cooling and trapping of atoms: beyond the limits › giamarchi › local › cuso › Aspect › ... · Laser cooling and trapping of atoms: beyond the limits 1.A breakthrough

Laser Cooling/Trapping of atoms

Narrow-Line Cooling Light for a Magneto-Optical Trap of Erbium Atoms

8. LASER COOLING AND TRAPPING OF NEUTRAL ATOMSatomcool.rice.edu/static/bradley_hulet_1996.pdf · 130 LASER COOLING AND TRAPPING OF NEUTRAL ATOMS methods discussed in other chapters

Laser cooling and trapping of atoms - Universiteit Utrechtstrat102/preprint/handpubl.pdfLaser cooling and trapping of atoms H.J. Metcalf and P. van der Straten Department of Physics,

Strontium Isotopes

Cooling effects in the Stark deceleration of Rydberg atoms

Strontium Dog

Laser cooling of atoms : Monte-Carlo wavefunction simulations · 2017-07-06 · Faculté des Sciences Appliquées Université de Liège Laser cooling of atoms : Monte-Carlo wavefunction

STRONTIUM TITANIUM DOUBLE METAL ALKOXIDE Safety Data …EU_English.pdf · DSRTI50 - STRONTIUM TITANIUM DOUBLE METAL ALKOXIDE STRONTIUM TITANIUM DOUBLE METAL ALKOXIDE Safety Data Sheet

DETERMINATION OF BARIUM AND STRONTIUM PEROXIDES … · DETERMINATION OF BARIUM AND STRONTIUM PEROXIDES ... A method is proposed for the determination of barium and strontium ... involve

A high-flux source of laser-cooled strontium atoms · 2019. 10. 1. · Strontium atom source (Singapore) –Multiple stages: atomic oven, transverse collimator, Zeeman slower, and

Trapping and cooling rubidium atoms for quantum information...Trapping and cooling rubidium atoms for quantum information dissertation by Herbert Crepaz submitted to the Faculty of

Laser-cooling and trapping (some history) › phys598aqg › fa... · Laser-cooling and trapping (some history) Theory (neutral atoms) Hansch & Schawlow, 1975 (trapped ions) Wineland&

Water quality — Strontium 90 and strontium 89 — Test

Atom Cooling Recycling Light · Atom Cooling Recycling Light A new theoretical analysis shows that laser photons used for cooling atoms have a unique thermal distribution that could

Creating Strontium Rydberg Atoms

Laser cooling of antihydrogen atoms