1. The Performance of Chip-Scale Atomic Clocks V. Gerginov 1, S. Knappe 2, P.D.D. Schwindt 3, V. Shah 2, J. Kitching 3, L. Hollberg 3 In collaboration with: J. Moreland 4, L. Liew 4, S. Song 4 Z. Popovic 2, A. Brannon 2 1 Also with University of Notre Dame, Notre Dame, IN 46556 2 Also with University of Colorado, Boulder, CO 80309 3 National Institute of Standards and Technology, Boulder, CO 80305 4 Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305

2. Primary Standard Compact Atomic Clock Loses 1 sec. in: 10 8 years 1000 years Size: 10 7 cm 3 100 cm 3 Power: kW 5 W Cost: $1 M $1,000 Higher Precision Smaller Size ??? CSAC 1000 years 1cm 3 30 mW $100 Wristwatch Quartz Crystal Precision Quartz Crystal 1 year 1 day 1 cm 3 10 -3 cm 3 30 mW 10  W $100 $1 Types of clocks

3. CPT-Based Chip-Scale Atomic Clock Arimondo et al., Lett. Nuovo Cim., 17, 333, 1976 Alzetta et al., Il Nuovo Cim. 36B, 5, 1976 Bell et al., Phys. Rev. Lett. 6, 280, 1961 11 22 11 22 2  RF =  1 -  2 =  12  12  RF

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

5. CSAC V

6. Local Oscillator Allan deviation Power Consumption 5 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 º C to 50 º C the range Tuning Range 3 MHz Size 0.49 cm 2 LO locked to table-top experiment LO locked to CSAC V A. Brannon et al., 2005 IEEE MTT-S Int. Microwave Symp Dig.

7. Clock Performance ParameterPowerComment Laser electrical2.5mWCurrent 1.8mA Laser heating55mW (45mW 1 )Temp. 80 o C Cell heating68mW (24mW 1 )Temp 85 o C Magn. field<0.1mW RF modulation0.6mW-2.5dBm Total126mW (72mW) 1 in vacuum Limitations on long-term stability: - environment temp. changes - laser parameter changes - CPT resonance drift

8. Components Optimization Cell performance (table top experiment) Cell dimensions 1x1x1mm Buffer gas Ar-Ne mixture CPT linewidth 1.2kHz @ 3% contrast (ratio CPT amplitude to optical absorption) S. Knappe et al., submitted to Optics Letters

9. Laser Performance (table top experiment) Local Oscillator Performance (table top experiment)

10. Conclusions 1.Atomic clock (physics package <1cm 3 ) operating below 100 mW 2.Local oscillator consuming 5mW locked to the physics package 3.Demonstrated 1mm 3 87 Rb vapor cell with reduced clock frequency drifts 4.Reduced clock sensitivity to laser temperature and LO power changes