A research group that includes Motoaki Hara, Senior Researcher at the National Institute of Information and Communications Technology (NICT, President: Hideyuki Tokuda, Ph.D.), developed a simple miniaturized atomic clock1 system, which does not require a complicated frequency multiplication2, as an outcome of a collaboration with Professor Takahito Ono of Tohoku University (President: Susumu Satomi) and Associate Professor Hiroyuki Ito of Tokyo Institute of Technology (President: Yoshinao Mishima).
We propose a new microwave generator that exploits thickness extensional (TE) vibration in a piezoelectric thin film3 to miniaturize an atomic clock. The TE mode is suitable for mechanical resonance at GHz frequencies, and can be synchronized directly to atomic resonance. Frequency multipliers and off-chip quartz oscillators, which are space- and power-hungry circuit blocks, are no longer necessary in the system. Furthermore, we originally developed a micro machined cell for alkali metal atoms to reduce the size and cost using a batch photo-fabrication. Consequently, we achieved a remarkable improvement in frequency stability. By transferring this technology into practical products, atomic clocks, which are deployed in high-end systems such as satellites or base stations, can be incorporated on smart phones.