An Optomechanical Cavity Oscillator as a Fifth-Coordinate Frequency Standard

Mechanical oscillators offer a route to frequency standards that are small, robust and integrable, but their stability is bounded by thermal noise. This paper computes that bound for a 5 MHz silicon optomechanical oscillator with quality factor 2.0e6 held at 4 K, intended to serve as the local oscillator disciplined by fifth-coordinate phase references. The computed Allan deviation is 2.64e-11 at one second and 2.64e-12 at one hundred seconds. The paper states plainly that this thermal floor falls short of the 1e-13 class stability that primary timing applications want, identifies the stored-energy and quality-factor changes that would close the gap, and thereby defines the development path rather than overselling the present design. The study is simulated; no oscillator has been measured.