Shinya Yanagimachi, Senior Researcher at the National Institute of Advanced Industrial Science and Technology, has developed a compact atomic clock that is extremely stable over the long term in collaboration with Tokyo Metropolitan University and Ricoh Corporation.
In recent years, accurate time information is important for the arrival of the full-scale IoT (Internet of Things) era, but it has been pointed out that conventional global navigation satellite systems such as GPS are vulnerable to radio interference. .. If a small and stable atomic clock can be mounted on an IoT terminal, it will be possible to autonomously diagnose and correct the accuracy of the time, thus ensuring safety.
Currently, the mainstream of small atomic clocks is to use coherent population trapping resonance, a resonance phenomenon derived from the interaction between light and atoms, to acquire information on the natural frequency of an atom.However, long-term time and frequency stability was limited by frequency fluctuations due to fluctuations in the light shift (change in the energy level of the atom due to the interaction between the irradiated laser beam and the atom).
This time, it was quantitatively elucidated that the secular change of the surface emission laser (VCSEL) oscillation wavelength is involved in the fluctuation of the light shift.However, direct suppression of light shift fluctuations increases power consumption.Therefore, we devised a driving method called the zero-cross method in which the natural frequency of cesium (Cs) atoms does not change even if the VCSEL oscillation wavelength changes over time, and applied it to a small atomic clock.
The effect of applying the zero-cross method was carefully verified after a long-term evaluation period of 150 days or more.As a result, the fluctuation of the natural frequency of the Cs atom can be sufficiently suppressed, and when the average time is about 50 days, we succeeded in obtaining 100 times the stability of the conventional small atomic clock.
Highly stable atomic clocks are expected to contribute to seamless data collection through IoT networks.In the future, it is said that it will proceed with research and development aimed at further stabilizing small atomic clocks.
