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Chip-Scale Atomic Clock Program (CSAC)
Program Manager: Dr. Amit Lal
The goal of the Chip-Scale Atomic Clock program is to create ultra-miniaturized, low-power, atomic time and frequency reference units that will achieve, relative to present approaches:
- >200X reduction in size (from 230 cm3 to <1 cm3),
- >300X reduction in power consumption (from 10 W to <30 mW), and
- Matching performance (1 X 10-11 accuracy ⇒ 1 µ/day). Example of future payoff is wristwatch size high-security UHF communicator / jam-resistant GPS receiver.
The development of Chip-Scale Atomic Clock will enable ultra-miniaturized (wristwatch in size) and ultra low power time and frequency references for high-security UHF communication and jam-resistant GPS receivers. The use of these ultra-miniature time reference units can greatly improve the mobility and robustness of any military systems and platforms with sophisticated UHF communication and/or navigation requirements. The ultra-stable frequency reference from atomic source will drastically improve channel selectivity and density for all military communications. It will also enable ultra-fast frequency hopping in synchronized spread-spectrum communication for improved security and jam resistance and strong-encryption in data communication. When used in military GPS receivers, it will greatly improve the jamming margin in a high-jamming environment, reacquisition capability, and position identification accuracy. In surveillance applications, chip-scale atomic clocks can be used to improve resolution in Doppler radars and to enhance accuracy of location identification of radio emitters. Other important uses include missile and munitions guidance, robust electronic and information defense networks, and high-confidence identification of friends and foes. All of these applications will be characterized by significant power reduction and/or ultra miniaturization while meeting or exceeding the performance levels of the state-of-practice approaches.
The key focus of this program is on optimized combinations of innovative solutions in micro or nano-fabrication, materials processing, device design, transduction mechanism, interconnects, and other relevant engineering approaches that directly address the performance issues in atomic frequency and time referencing. The most essential research elements include confinement and stabilization of cesium, rubidium, or other suitable species, excitation and detection of the hyperfine-transition resonance of the chosen species, and phase locking or direct coupling with micromechanical resonators. Research issues include, among others: (1) temperature stability, magnetic shielding, hermetic encapsulation, and means to maintain atomic ground-state coherence within the confinement cell; (2) integration with vertical cavity surface emitting laser (VSCEL) or other photon and/or microwave sources and photo detector with the confinement cell; and (3) integration, phase locking, and/or direct coupling with micromechanical resonators.
Phased technology development approaches are planned. The first phase focuses on establishing theoretical limits of chip-scale atomic clocks and demonstrating practical design and fabrication feasibilities. Several alternatives design and fabrication techniques will be explored, and the most promising ones will be down selected. Phase 2 aims at demonstrating individual components of ultra-miniaturized atomic confinement cells, GHz nano resonators, atomic-resonance-coupled resonators, and phase-locked and interface circuits. Each component will be based on robust design for temperature stability and magnetic shielding. Phase 3 will be the final chip-level integration, focusing on demonstrating operational chip-scale atomic clock and integration with CMOS circuits (Si, Si-Ge, or III-V electronics). Throughout the entire three phases, potential DOD users will be engaged to identify DOD operational requirements and to set the stage for DOD transition. Implementing chip-scale atomic clocks for high-security UHF communication and jam-resistant GPS receivers will be potential transition activities within DOD.