Compact Micro-fabricated Optomechanical Accelerometers

Abstract:

Miniaturized accelerometers are a promising technology with applications in geodesy as a compact, portable and cost-effective inertial sensing technology with observation continuity. The size, weight, and power (SWaP) characteristics are compatible with compact spacecraft platforms such as CubeSats. Using low loss materials, we are developing and improving the design of compact micro-fabricated quasi-monolithic optomechanical accelerometers for use in future GRACE-like mass change missions. These accelerometers aim for high sensitivities at low frequencies with an acceleration noise floor between 10^-10 m s^-2/√Hz and 10^-11 m s^-2/√Hz in the 10 mHz to 3 Hz range and a mechanical quality factor of Q_m = 200,000. An integral component of our optomechanical accelerometers is the test mass laser-interferometric displacement sensor. We are developing compact quasi-monolithic heterodyne laser interferometers that provide a high common-mode rejection ratio to environmental disturbances using highly common optical paths. This allows for long-term noise reduction, as well as high sensitivity and stability. Breadboard prototypes operating in our laboratory at a wavelength of 632.8 nm in air have demonstrated displacement sensitivities at the picometer level with frequencies above 100 mHz. In-vacuum performance is expected to be significantly higher and measurement runs are currently underway. In addition, we are redesigning these sensors to operate at near-infrared wavelengths of 1064 nm and 1550 nm where more stable and cost-effective laser units are available. We will be developing and testing packaging of these accelerometers for a space flight instrument prototype that preserves the high mechanical quality factor. In this presentation we will discuss our current designs and laboratory results.