Calibration and temperature measurement of levitated optomechanical sensors

TL;DR

This paper introduces calibration protocols for levitated nanoparticle sensors, addressing anharmonicities and unknown bath temperatures, enabling accurate displacement and temperature measurements for enhanced precision sensing.

Contribution

The paper presents novel calibration methods for levitated nanoparticles, including anharmonicity correction and a harmonic driving protocol for unknown heat bath conditions.

Findings

Calibration protocols improve measurement accuracy

Temperature of levitated particles can be precisely determined

Protocols are applicable under various thermal conditions

Abstract

Optically levitated nanoparticles offer enormous potential for precision sensing. However, as for any other metrology device, the absolute measurement performance of a levitated-particle sensor is limited by the accuracy of the calibration relating the measured signal to an absolute displacement of the particle. Here, we suggest and demonstrate calibration protocols for levitated-nanoparticle sensors. Our calibration procedures include the treatment of anharmonicities in the trapping potential, as well as a protocol using a harmonic driving force, which is applicable if the sensor is coupled to a heat bath of unknown temperature. Finally, using the calibration, we determine the center-of-mass temperature of an optically levitated particle in thermal equilibrium from its motion, and discuss the optimal measurement time required to determine said temperature.