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An on-chip fully electronic molecular clock based on sub-terahertz rotational spectroscopy

Nature Electronics volume 1, pages 421–427 (2018)Cite this article

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Abstract

Mobile electronic devices require stable, portable and energy-efficient frequency references (or clocks). However, current approaches using quartz-crystal and microelectromechanical oscillators suffer from frequency drift. Recent advances in chip-scale atomic clocks, which probe the hyperfine transitions of evaporated alkali atoms, have led to devices that can overcome this issue, but their complex construction, cost and power consumption limit their broader deployment. Here we show that sub-terahertz rotational transitions of polar gaseous molecules can be used as frequency bases to create low-cost, low-power miniaturized clocks. We report two molecular clocks probing carbonyl sulfide (16O12C32S), which are based on laboratory-scale instruments and complementary metal–oxide–semiconductor chips. Compared with chip-scale atomic clocks, our approach is less sensitive to external influences and offers faster frequency error compensation, and, by eliminating the need for alkali metal evaporation, it offers faster start-up times and lower power consumption. Our work demonstrates the feasibility of monolithic integration of atomic-clock-grade frequency references in mainstream silicon-chip systems.

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Fig. 1: Rotational spectrum of OCS in a WR-4.3 waveguide gas cell.
Fig. 2: Experimental results and analysis of the OCS spectral line at f0 = 267.530239 GHz.
Fig. 3: Laboratory-scale molecular clock.
Fig. 4: Measured stability of the laboratory-scale molecular clock.
Fig. 5: Chip-scale molecular clock on silicon and the measurement results.

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References

  1. Audoin, C. & Guinot, B. The Measurement of Time, Frequency and the Atomic Clock (Cambridge Univ. Press, Cambridge, 2001).

  2. Lombardi, M. A. in The Mechatronics Handbook (ed. Bishop, R. H.) Ch. 17 (CRC Press, New York, NY, 2001).

  3. Nguyen, C. T. C. MEMS technology for timing and frequency control. IEEE Trans. Ultrason. Ferroelectr. Freq. Control. 54, 251–270 (2007).

    Article  Google Scholar 

  4. Fifty years of atomic time-keeping: 1955 to 2005. Special Issue. Metrologia 42, S1–S156 (2005).

  5. Lombardi, M. A., Heavner, T. P. & Jefferts, S. R. NIST primary frequency standards and the realization of the SI second. NCSL Int. Meas. 2, 74–89 (2007).

    Article  Google Scholar 

  6. Lutwak, R. Principles of atomic clocks. In IEEE Int. Frequency Control Symp. (IEEE, 2011).

  7. Alzetta, G., Gozzini, A., Moi, L. & Orriols, G. An experimental method for the observation of R.F. transitions and laser beat resonances in oriented Na vapour. Nuovo Cim. B 36, 5–20 (1976).

    Article  Google Scholar 

  8. Arimondo, E. & Orriols, G. Nonabsorbing atomic coherences by coherent two-photon transitions in a three-level optical pumping. Lett. Al Nuovo Cim. 17, 333–338 (1976).

    Article  Google Scholar 

  9. Cyr, N., Tetu, M. & Breton, M. All-optical microwave frequency standard: a proposal. IEEE Trans. Instrum. Meas. 42, 640–649 (1993).

    Article  Google Scholar 

  10. Vanier, J. Atomic clocks based on coherent population trapping: a review. Appl. Phys. B 81, 421–442 (2005).

    Article  Google Scholar 

  11. Knappe, S. et al. A microfabricated atomic clock. Appl. Phys. Lett. 85, 1460–1462 (2004).

    Article  Google Scholar 

  12. Lutwak, R. et al. The chip-scale atomic clock—prototype evaluation. In 39th Ann. Precise Time and Time Interval Meeting 269–290 (ION, 2007).

  13. Youngner, D. et al. A manufacturable chip-scale atomic clock. In Solid-State Sensors, Actuators and Microsystems Conference 2007, 39–44 (IEEE, 2007).

  14. DeNatale, J. et al. Compact, low-power chip-scale atomic clock. In Position, Location and Navigation Symposium 2008, 67–70 (IEEE, 2008).

  15. Haesler, J. et al. The integrated Swiss miniature atomic clock. In Joint European Frequency and Time Forum & International Frequency Control Symposium (EFTF/IFC) 2013, 579–581 (IEEE, 2013).

  16. Quantum SA.45s chip scale atomic clock (Microsemi, 2017); https://www.microsemi.com/document-portal/doc_download/133305-sa-45s-csac-datasheet

  17. Riley, W. Handbook of Frequency Stability Analysis (NIST, Gaithersburg, MD, 2008).

  18. Shock and vibration testing of the SA.45s chip scale atomic clock (CSAC) validation build units (Microsemi, 2014); https://www.microsemi.com/document-portal/doc_download/133153-shock-and-vibration-testing-of-the-sa-45s-chip-scale-atomic-clock-csac-validation-build-units

  19. Good, W. E. The inversion spectrum of ammonia. Phys. Rev. 70, 213–218 (1946).

    Article  Google Scholar 

  20. Smith, W. V., Quevedo, J. L. G. D., Carter, R. L. & Bennett, W. S. Frequency stabilization of microwave oscillators by spectrum lines. J. Appl. Phys. 18, 1112–1115 (1947).

    Article  Google Scholar 

  21. Hershberger, W. D. & Norton, L. E. Frequency stabilization with microwave spectral lines. RCA Rev. 9, 38–49 (1948).

    Google Scholar 

  22. Townes, C. H. Atomic clocks and frequency stabilization on microwave spectral lines. J. Appl. Phys. 22, 1365–1372 (1951).

    Article  Google Scholar 

  23. Gordon, J. P., Zeiger, H. J. & Townes, C. H. Molecular microwave oscillator and new hyperfine structure in the microwave spectrum of NH3. Phys. Rev. 95, 282–284 (1954).

    Article  Google Scholar 

  24. Wineland, H. D. A., David, J. & Hellwig, H. Special purpose atomic (molecular) standard. In Proc. Eighth Annual Precise Time and Material Interval Applications and Planning Meeting 429–448 (IEEE, 1977).

  25. Townes, C. H. & Schawlow, A. L. Microwave Spectroscopy (Courier Corporation, Chelmsford, MA, 2013).

  26. Wineland, D. J., Howe, D. A. & Mohler, M. B. Results with the special-purpose ammonia frequency standard. In 31st Ann. Symp. on Frequency Control 1977, 562–573 (IEEE, 1977).

  27. Wang, C. & Han, R. Rapid and energy-efficient molecular sensing using dual mm-wave combs in 65 nm CMOS: a 220-to-320 GHz spectrometer with 5.2 mW radiated power and 14.6-to-19.5 dB noise figure. In International Solid-State Circuit Conference (ISSCC), 18–20 (IEEE, 2017).

  28. Ferm, R. J. The chemistry of carbonyl sulfide. Chem. Rev. 57, 621–640 (1957).

    Article  Google Scholar 

  29. Cox, J. T. & Gordy, W. Zeeman effect of some linear and symmetric-top molecules. Phys. Rev. 101, 1298–1304 (1956).

    Article  Google Scholar 

  30. Vanier, J. & Bernier, L.-G. On the signal-to-noise ratio and short-term stability of passive rubidium frequency standards. IEEE Trans. Instrum. Meas. 1001, 277–282 (1981).

    Article  Google Scholar 

  31. Karplus, R. & Schwinger, J. A note on saturation in microwave spectroscopy. Phys. Rev. 73, 1020–1026 (1948).

    Article  MATH  Google Scholar 

  32. Supplee, J. M., Whittaker, E. A. & Lenth, W. Theoretical description of frequency modulation and wavelength modulation spectroscopy. Appl. Opt. 33, 6294–6302 (1994).

    Article  Google Scholar 

  33. Wang, C. et al. CMOA molecular clock probing 231.061-GHz rotational line of OCS with sub-ppb long-term stability and 66-mW dc power. In 2018 Symp. on VLSI Technology and Circuits (IEEE, 2018).

  34. Wang, C. et al. Robust sub-harmonic mixer at 340 GHz using intrinsic resonances of hammer-head filter and improved diode model. J. Infrared Millim. Terahertz Waves 38, 1397–1415 (2017).

    Article  Google Scholar 

  35. Jet Propulsion Laboratory molecular spectroscopy catalog; https://spec.jpl.nasa.gov/

  36. Hati, A., Nelson, C. & Howe, D. in Aerial Vehicles 259–286 (In-Tech, Vienna, 2009).

  37. Koshelev, M. A., Tretyakov, M. Y., Rohart, F. & Bouanich, J.-P. Speed dependence of collisional relaxation in ground vibrational state of OCS: rotational behaviour. J. Chem. Phys. 136, 124316 (2012).

    Article  Google Scholar 

  38. Yang, S. H., Baek, K. J., Kwon, T. Y., Kim, Y. B. & Lee, H. S. Second-order Zeeman frequency shift in the optically pumped cesium beam frequency standard with a dual servo system. Jpn J. Appl. Phys. 38, 6174–6177 (1999).

    Article  Google Scholar 

  39. GATS, I. Spectral Calculator; http://www.spectralcalc.com

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Acknowledgements

The authors thank S. Coy (MIT, Department of Chemistry), R. Field (MIT, Department of Chemistry), D. Buss (Texas Instruments and MIT, Department of Electrical Engineering and Computer Science), B. Perkins (MIT Lincoln Labs), J. Muenter (University of Rochester, Department of Chemistry) and P. Nadeau (MIT, Department of Electrical Engineering and Computer Science) for helpful technical discussions. The authors also thank Y. Zhang and K. Nelson (MIT, Department of Chemistry) for help with OCS preparation and other technical support. This work was supported by an NSF CAREER award (ECCS-1653100), MIT Lincoln Laboratory, MIT Center of Integrated Circuits and Systems, and a Texas Instrument Fellowship.

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  1. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA

    Cheng Wang, Xiang Yi, James Mawdsley, Mina Kim, Zihan Wang & Ruonan Han

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  1. Cheng Wang
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  2. Xiang Yi
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Contributions

C.W. and R.H. conceived and designed the research. C.W. constructed the two prototypes (including the laboratory-scale and chip-scale molecular clocks). X.Y. conducted the design of the VCXO and analysis of the clock-loop dynamics. C.W., M.K. and Z.W. conducted spectroscopy experiments. C.W. and J.M. conducted clock stability characterization. C.W. and R.H. analysed the data and wrote the manuscript. All authors reviewed the manuscript.

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Correspondence to Ruonan Han.

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Wang, C., Yi, X., Mawdsley, J. et al. An on-chip fully electronic molecular clock based on sub-terahertz rotational spectroscopy. Nat Electron 1, 421–427 (2018). https://doi.org/10.1038/s41928-018-0102-4

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