NASA’s Jet Propulsion Laboratory has developed a neutral mounting scheme that eliminates the acceleration sensitivity of whispering gallery mode resonators (WGMRs), making them suitable for use in high-precision portable instruments such as optical atomic clocks and high-resolution laser ranging systems. With state-of-the-art WGMR mounting schemes, accelerations induce deformations in the resonator structure, changing its resonant frequency and limiting their usefulness in precision devices. JPL’s novel coaxial mounting scheme is capable of reducing and even eliminating these vibration- and acceleration-induced frequency fluctuations, yielding a WGMR with superior frequency stability that can be used for creating ultra-compact, highly stabilized lasers that are ideally suited for use in spectroscopy, sensing, and frequency metrology applications.

The finite element numerical results show the disc-resonator deformed from the neutral coaxial mounting scheme. Colors represent the magnitude of radial deformation, and a band where this deformation is zero can be seen along the perimeter of the disc.

With a neutral mounting architecture, the mounting forces are distributed such that the deformation of the optical cavity is null in a given direction, regardless of their amplitudes. This can guarantee that mechanical fluctuations are not transferred to a cavity-length deformation (i.e., to the resonance frequency). Whispering gallery mode disc resonators can only be loaded through normal stresses exerted on the top and bottom surfaces of the disc by clamping the disc between two cylinders with different radii. This neutral mounting scheme creates a radial displacement field that is null at the rim of the disc, regardless of the mounting force intensity.

Finite element method simulations of a coaxially clamped WGMR have been performed using the following disc dimensions and geometries: inner radius a = 2 mm, outer radius b = 5 mm, thickness = 0.5 mm, and disc symmetry plane aligned on the z axis. The material properties of the disc were based on those of calcium fluoride. The simulations show that optimal mounting configurations are quite robust and can significantly improve frequency stability under a wide range of loading forces.

Potential applications include a small and robust frequency reference for portable and practical devices, laser devices, chemical sensing, navigation, aerospace, frequency metrology, data transfer, and scientific instrumentation.

NASA is actively seeking licensees to commercialize this technology. Please contact Mark W. Homer at Mark.W.Homer@ jpl.nasa.gov to initiate licensing discussions. Follow this link for more information: http://technology.nasa.gov/patent/TB2016/NPO-TOPS-23 .

Refer to NPO-48539-1.


NASA Tech Briefs Magazine

This article first appeared in the October, 2016 issue of NASA Tech Briefs Magazine.

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