arXiv subjects

John R. Lawall

Publications and source records attributed to John R. Lawall.

3 recordsLinked to original sources

arXiv2026

Fast, optimal readout of a tethered optomechanical pressure sensor

We demonstrate a fast readout method for tethered optomechanical pressure sensors. The fast readout method allows mechanical ring-down measurement rates that exceed the total mechanical damping rate $Γ_t$. We model the uncertainty of our ring-down measurements with the Cramér-Rao bound, including the effect of thermomechanical noise. Both our data and the Cramér-Rao bound indicate that measurement rates on the order of the mechanical damping rate produce the lowest uncertainty. At low pressures, using the optimal measurement rate allows 10$\times$ faster measurements or 3$\times$ lower uncertainty compared to allowing our sensor to ring down to the thermomechanical noise floor. Our results allow tethered optomechanical pressure sensors to operate at rates comparable to commercially available pressure gauges, removing an obstacle to adoption of optomechanical pressure sensors in industrial settings.

physics.app-ph↗

arXiv2026

Molecularly Thin Polyaramid Nanomechanical Resonators

Two-dimensional polyaramids exhibit strong hydrogen bonding to create molecularly thin nanosheets analogous to graphene. Here, we report the first nanomechanical resonators made out of a two-dimensional polyaramid, 2DPA-1, with thicknesses as small as 8 nm. To fabricate these molecular-scale resonators, we transferred nanofilms of 2DPA-1 onto chips with previously etched arrays of circular microwells. We then characterized the thermal resonances of these resonators under different conditions. When there is no residual gas inside the 2DPA-1-covered microwells, the eigenfrequencies are well-described by a tensioned plate theory, providing the Young's modulus and tension of the 2DPA-1 nanofilms. With gas present, the nanofilms bulge up and mechanical resonances are modified due to the adhesion, bulging and slack present in the system. The fabrication and mechanical characterization of these first 2DPA-1 nanomechanical resonators represent a convincing path toward molecular-scale polymeric NEMS with high mechanical strength, low density, and synthetic processability.

cond-mat.mes-hall↗

arXiv2025

Accurate, precise pressure sensing with tethered optomechanics

We show that optomechanical pressure sensors with characterized density and thickness can achieve uncertainty as low as 1.1 % via comparison with a secondary pressure standard. The agreement between the secondary standard and our optomechanical sensors is a necessary step towards using optomechanical devices as primary pressure sensors. Our silicon nitride and silicon carbide sensors are short-term and long-term stable, displaying Allan deviations compatible with better than 1 % precision and baseline drift significantly lower than the secondary standard. Our measurements also yield the in situ thin-film density of our sensors with 1 % total uncertainty or lower, aiding development of other optomechanical sensors. Our results demonstrate that optomechanical pressure sensors can achieve accuracy, precision, and drift sufficient to replace high performance legacy pressure gauges.

physics.app-ph↗