The Performance of Chip-Scale Atomic Clocks

V. Gerginov1, S. Knappe2, P.D.D. Schwindt3, V. Shah2, J. Kitching3, L. Hollberg3

In collaboration with:

J. Moreland4, L. Liew4, S. Song4

Z. Popovic2, A. Brannon2

1Also with University of Notre Dame, Notre Dame, IN 465562Also with University of Colorado, Boulder, CO 80309

3National Institute of Standards and Technology, Boulder, CO 80305

4Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305

PrimaryStandard

CompactAtomic Clock

Loses 1 sec. in: 108 years 1000 years Size: 107 cm3 100 cm3 Power: kW 5 W Cost: $1 M $1,000

Higher Precision

Smaller Size

???

CSAC

1000 years 1cm3

30 mW$100

WristwatchQuartz Crystal

PrecisionQuartz Crystal

1 year 1 day1 cm3 10-3 cm3

30 mW 10 W$100 $1

Types of clocks

CPT-Based Chip-Scale Atomic Clock

Arimondo et al., Lett. Nuovo Cim., 17, 333, 1976 Alzetta et al., Il Nuovo Cim. 36B, 5, 1976Bell et al., Phys. Rev. Lett. 6, 280, 1961

1 2

12

2RF= 1- 2= 12

12

RF

Clock Assembly

Micromachined Vapor Cell Atomic ClockJ. Kitching, S. Knappe and L. Hollberg, Appl. Phys. Lett., 81, 553, 2002S. Knappe, L. Liew, V. Shah, P. Schwindt, J. Moreland, L. Hollberg and J. Kitching, Appl. Phys. Lett. 85, 1460, 2004

CSAC V

Local Oscillator

Alla

n de

viat

ion

Power Consumption5 mW DC at 1.6V

Phase Noise -92dBc / Hz @ 10kHz offset -33dBc / Hz @ 100Hz offset

RF Output Power -6dBm to -9dBm @ 3.417 GHz

Thermal drift 0ppm / K at room temperature -17ppm / K avg. over 0 ºC to 50 ºC the range

Tuning Range3 MHz

Size0.49 cm2

LO locked to table-top experiment

LO locked to CSAC V

A. Brannon et al., 2005 IEEE MTT-S Int. Microwave Symp Dig.

Clock PerformanceParameter Power Comment

Laser electrical

2.5mW Current 1.8mA

Laser heating 55mW (45mW1) Temp. 80oC

Cell heating 68mW (24mW1) Temp 85oC

Magn. field <0.1mW

RF modulation 0.6mW -2.5dBm

Total 126mW (72mW)

1in vacuum

Limitations on long-term stability:- environment temp. changes- laser parameter changes - CPT resonance drift

Components OptimizationCell performance (table top experiment)

Cell dimensions 1x1x1mmBuffer gas Ar-Ne mixtureCPT linewidth 1.2kHz @ 3% contrast (ratio CPT amplitude to optical absorption)

S. Knappe et al., submitted to Optics Letters

Laser Performance (table top experiment)

Local Oscillator Performance (table top experiment)

Conclusions

1. Atomic clock (physics package <1cm3 ) operating below 100 mW

2. Local oscillator consuming 5mW locked to the physics package

3. Demonstrated 1mm3 87Rb vapor cell with reduced clock frequency drifts

4. Reduced clock sensitivity to laser temperature and LO power changes