arXiv subjects

Jon R. Pratt

Publications and source records attributed to Jon R. Pratt.

5 recordsLinked to original sources

arXiv2026

Dual mass milligram-scale torsion oscillator for vibration-free optomechanical sensing

Chip-scale optomechanical devices are driving the miniaturization of inertial sensors and next generation fundamental physics experiments. However, precision at the theoretical limit is often unattainable due to extraneous vibrations. One solution is tailoring the device to isolate a degree of freedom from the environment while maintaining coupling to the signal of interest. To this end, we introduce a dual milligram-mass torsion oscillator, formed by mass loading a strained silicon nitride nanoribbon. The antisymmetric torsion mode suppresses vibrations by over an order of magnitude to achieve a thermally limited torque sensitivity of $10^{-18}$ Nm/$\sqrt{\rm Hz}$ while maintaining ultralow loss. We demonstrate the sensing ability by detecting an optical radiation pressure torque of $10^{-16}$ Nm over a 30 Hz bandwidth. We also characterize the device for frequency-based gravimetry, demonstrating $10^{-6}g_0$ ($g_0=9.8$ $\rm m s^{-2}$) precision in 30 seconds with an oscillation amplitude of only 100 $\mu$rad. This device demonstrates a technique for overcoming vibration noise, with broad implications for optomechanical sensing from commercial applications to fundamental physics experiments.

physics.app-ph↗

arXiv2026

Nanofabricated torsion pendulums for tabletop gravity experiments

Measurement of mutual gravitation on laboratory scales is an outstanding challenge and a prerequisite to probing theories of quantum gravity. A leading technology in tabletop gravity experiments is the torsion balance, with limitations due to thermal decoherence. Recent demonstrations of lithographically defined suspensions in thin-film silicon nitride with macroscale test masses suggest a path forward, as torsion pendulums dominated by gravitational stiffness may achieve higher mechanical quality factors through dilution of material losses. Here we demonstrate a 250 micron by 5 mm by 1.8 micron torsion fiber supporting 87 grams and forming a Cavendish-style torsion pendulum with tungsten test masses that -- to our knowledge -- is the largest thin-film silicon-nitride-based oscillator to date. Torsion pendulums with thin-film, nanofabricated suspensions provide a test bed for near-term tabletop experiments probing classical and quantum gravitational interaction between oscillators.

physics.ins-det↗

arXiv2021

Nanoscale torsional dissipation dilution for quantum experiments and precision measurement

We show that torsion resonators can experience massive dissipation dilution due to nanoscale strain, and draw a connection to a century-old theory from the torsion balance community which suggests that a simple torsion ribbon is naturally soft-clamped. By disrupting a commonly held belief in the nanomechanics community, our findings invite a rethinking of strategies towards quantum experiments and precision measurement with nanomechanical resonators. For example, we revisit the optical lever technique for monitoring displacement, and find that the rotation of a strained nanobeam can be resolved with an imprecision smaller than the zero-point motion of its fundamental torsional mode, without the use of a cavity or interferometric stability. We also find that a strained torsion ribbon can be mass-loaded without changing its $Q$ factor. We use this strategy to engineer a chip-scale torsion balance whose resonance frequency is sensitive to micro-$g$ fluctuations of the local gravitational field. Enabling both these advances is the fabrication of high-stress Si$_3$N$_4$ nanobeams with width-to-thickness ratios of $10^4$ and the recognition that their torsional modes have $Q$ factors scaling as their width-to-thickness ratio squared, yielding $Q$ factors as high as $10^8$ and $Q$-frequency products as high as $10^{13}$ Hz.

cond-mat.mes-hall↗

arXiv2015

Optomechanical reference accelerometer

We present an optomechanical accelerometer with high dynamic range, high bandwidth and read-out noise levels below 8 $μ$g/$\sqrt{\mathrm{Hz}}$. The straightforward assembly and low cost of our device make it a prime candidate for on-site reference calibrations and autonomous navigation. We present experimental data taken with a vacuum sealed, portable prototype and deduce the achieved bias stability and scale factor accuracy. Additionally, we present a comprehensive model of the device physics that we use to analyze the fundamental noise sources and accuracy limitations of such devices.

physics.optics↗

arXiv2014

A self-calibrating optomechanical force sensor with femtonewton resolution

We report the development of an ultrasensitive optomechanical sensor designed to improve the accuracy and precision of force measurements with atomic force microscopy. The sensors reach quality factors of 4.3x10^6 and force resolution on the femtonewton scale at room temperature. Self-calibration of the sensor is accomplished using radiation pressure to create a reference force. Self-calibration enables in situ calibration of the sensor in extreme environments, such as cryogenic ultra-high vacuum. The senor technology presents a viable route to force measurements at the atomic scale with uncertainties below the percent level.

cond-mat.mes-hall↗