Mechanical quality factor estimation from a nonlinear optical cavity response
Abstract
Intrinsic damping rate and quality factor (Q) are key parameters in optomechanical systems. However, in high-Q devices, their measurement is often challenging because probe-induced dynamical backaction (DBA) and the need to resolve and accurately track the mechanical resonance limit the performance of state-of-the-art techniques. Here, we introduce an all-optical ringdown method in the unresolved-sideband regime that exploits the nonlinear, time-averaged optical response induced by strong mechanical motion. We derive an analytical model of the time-averaged optical cavity response probed by a weak frequency-scanning laser. During the evolution of the mechanical oscillator, the excited motion modulates the Lorentzian lineshape into a double-horned profile whose peak separation enables an accurate estimation of the modulation amplitude. Tracking this response during the mechanical ringdown allows the intrinsic damping rate to be determined without resolving the mechanical oscillation. We apply the method to a density-modulated phononic crystal membrane placed inside a high-finesse cavity and obtain mechanical quality factors consistent with independent measurements on the same platform. Our method requires a minimal optical setup, while offering an in situ diagnostic and reduced impact from probe-induced DBA and robustness against measurement noise. Finally, the model can describe other resonant systems dispersively coupled to coherent frequency modulations, providing new insights and measurement strategies that expand beyond the optomechanical platform.
Related
- Parameter Estimation for Eccentric Supermassive Black Hole Binaries with Pulsar Timing Arrays
- Fractal Colonization of Prebiotic Niches: Mechanical Budding of Nano-vesicles and Kinetic Resource Depletion as an Oncological Atavism
- A deep learning algorithm for black hole spin estimation using hot spot secondary images
- Probabilistic redshift estimation of undetected galaxies from multi-band background light maps
- CosmoForge. I. A unified framework for quadratic maximum likelihood power spectrum estimation and pixel-based likelihood analysis
BibTeX
@misc{ali2026mechanical,
title = {{Mechanical quality factor estimation from a nonlinear optical cavity response}},
author = {Zohran Ali and Davide Tomasella and Daniel Allepuz-Requena and Alexander Huck and Ulrik Lund Andersen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.07393},
eprint = {2609.07393},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07393},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Mechanical quality factor estimation from a nonlinear optical cavity response
AU - Zohran Ali
AU - Davide Tomasella
AU - Daniel Allepuz-Requena
AU - Alexander Huck
AU - Ulrik Lund Andersen
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2609.07393
UR - https://arxiv.org/abs/2609.07393
AB - Intrinsic damping rate and quality factor (Q) are key parameters in optomechanical systems. However, in high-Q devices, their measurement is often challenging because probe-induced dynamical backaction (DBA) and the need to resolve and accurately track the mechanical resonance limit the performance of state-of-the-art techniques. Here, we introduce an all-optical ringdown method in the unresolved-sideband regime that exploits the nonlinear, time-averaged optical response induced by strong mechanical motion. We derive an analytical model of the time-averaged optical cavity response probed by a weak frequency-scanning laser. During the evolution of the mechanical oscillator, the excited motion modulates the Lorentzian lineshape into a double-horned profile whose peak separation enables an accurate estimation of the modulation amplitude. Tracking this response during the mechanical ringdown allows the intrinsic damping rate to be determined without resolving the mechanical oscillation. We apply the method to a density-modulated phononic crystal membrane placed inside a high-finesse cavity and obtain mechanical quality factors consistent with independent measurements on the same platform. Our method requires a minimal optical setup, while offering an in situ diagnostic and reduced impact from probe-induced DBA and robustness against measurement noise. Finally, the model can describe other resonant systems dispersively coupled to coherent frequency modulations, providing new insights and measurement strategies that expand beyond the optomechanical platform.
ER -