Compact Optical Frequency Synthesizer

ABSTRACT: AOSense proposes to design a compact and robust optical frequency synthesizer with a volume of<2 liters that will be capable of producing a stable microwave frequency of ~100 MHz, as well as an optical output. The system is based on the integration of a narrow-linewidth laser stabilized to a high-finesse optical cavity and a fiber-based optical frequency comb, which transfers the frequency stability of the laser to the microwave output. We anticipate the frequency stability of the laser will be limited to 1E-14 at 1 second of integration time by the optical cavity. The corresponding phase noise performance of the microwave output exceeds the performance of commercial quartz and sapphire oscillators and will enable improved capability for a variety of applications such as radar, communication, and high-speed electronics. The optical output of the system can be stabilized to an atomic transition to provide long-term stability, as well as serve as a readout of the transition frequency. Such a readout system is an integral part of next generation optical atomic clocks that will provide improvements in timing and synchronization, as well as navigation in GPS limited or denied environments. BENEFIT: The proposed device will benefit a number of DoD and commercial applications listed below. Low phase noise microwave generator: The frequency comb system can generate microwave signals with better phase noise performance than commercial quartz and sapphire oscillators by utilizing optical frequency division. The improved phase noise performance directly leads to improved capability for radar, communication and high-speed electronics vital to DoD applications. Optical atomic clock readout: The frequency comb system can be integrated with an optical atomic clock to discipline the clock laser and serve as a readout system for the clock. Such an integrated system will provide improved timing and synchronization to increase robustness of the GPS system, as well as provide accurate timing in GPS denied environments. Optical frequency synthesizer: There is a small, but growing market for frequency combs for laboratory use beyond metrology labs at government institutes. As the system cost comes down, optical synthesizers that can output requested optical frequency with Hz precision will become commonplace in most military, commercial R & D, and academic labs utilizing laser light.