Optimal displacement detection of arbitrarily-shaped levitated dielectric objects using optical radiation

TL;DR

This paper introduces a Fisher information-based method for optimal displacement detection of arbitrarily-shaped levitated dielectric objects, enhancing precision in optomechanical sensing regardless of particle geometry.

Contribution

It develops a numerically implementable approach for optimal detection applicable to any particle shape, validated against existing methods for spherical particles and analyzed for practical non-spherical geometries.

Findings

Method agrees with prior spherical particle detection techniques.

Demonstrates detection limits for high-aspect-ratio disc-like particles.

Analyzes detection limits for rod-shaped particles in experimental configurations.

Abstract

Optically-levitated dielectric objects are promising for precision force, acceleration, torque, and rotation sensing due to their extreme environmental decoupling. While many levitated opto-mechanics experiments employ spherical objects, for some applications non-spherical geometries offer advantages. For example, rod-shaped or dumbbell shaped particles have been demonstrated for torque and rotation sensing and high aspect ratio plate-like particles can exhibit reduced photon recoil heating and may be useful for high-frequency gravitational wave detection or as high bandwidth accelerometers. To achieve optimal sensitivity, cooling, and quantum control in these systems, it is beneficial to achieve optimal displacement detection using scattered light. We describe and numerically implement a method based on Fisher information that is applicable to suspended particles of arbitrary geometry. We demonstrate the agreement between our method and prior methods employed for spherical particles, both in the Rayleigh and Lorentz-Mie regimes. As practical examples we analyze the optical detection limits of an optically-levitated high-aspect-ratio disc-like dielectric object and a rod-shaped object for configurations recently realized in experimental work.