RF Oscillators Based on Piezoelectrically Driven Optical Modulation

This paper investigates the use of piezoelectrically actuated acousto-optic modulators as a building block for generating electronic frequency references at radio frequencies (RFs). Similar to the concept of an optoelectronic oscillator, this approach leverages the strengths of multiple domains such as strong photonic confinement with optical resonances and the inherent compact RF filtering capabilities of piezoelectric resonators. An initial oscillator demonstration is constructed around an integrated aluminum nitride acousto-optic modulator, with a center frequency of 653 MHz. Phase noise of this device is analyzed and matched with the measured results, including the various contributors to input noise power density. This model allows us to determine anticipated figures for phase noise performance on par with the state of the art based on future improvements to the acousto-optic modulator.