Precision Mass and Density Measurement of Individual Optically Levitated Microspheres

Abstract

We report an $\text{in situ}$ mass measurement of approximately-$4.7\text{-}\mu$m-diameter, optically levitated microspheres with an electrostatic co-levitation technique. The mass of a trapped, charged microsphere is measured by holding its axial (vertical) position fixed with an optical feedback force, under the influence of a known electrostatic force. A mass measurement with $1.8\%$ systematic uncertainty is obtained by extrapolating to the electrostatic force required to support the microsphere against gravity in the absence of optical power. In three cases, the microspheres are recovered from the trap on a polymer-coated silicon beam and imaged with an electron microscope to measure their radii. The simultaneous precision characterization of the mass and radius of individual microspheres implies a density of $1.55\pm 0.08$g/cm${}^3$. The ability to recover individual microspheres from an optical trap opens the door to further diagnostics.

arXiv comment7 pages, 5 figures

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Cited by in corpus (14)

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• Robust optical-levitation-based metrology of nanoparticle's position and mass
• Search for non-Newtonian interactions at micrometer scale with a levitated test mass
• High sensitivity, levitated microsphere apparatus for short-distance force measurements
• Probing the screening of the Casimir interaction with optical tweezers
• Measurement of single nanoparticle anisotropy by laser induced optical alignment and Rayleigh scattering for determining particle morphology
• Absolute pressure and gas species identification with an optically levitated rotor
• Mechanical detection of nuclear decays
• Technique for rapid mass determination of airborne micro-particles based on release and recapture from an optical dipole force trap
• Librational Feedback Cooling
• Collision-resolved pressure sensing
• A nano vacuum gauge based on second-order coherence in optical levitation
• Optomechanical vector sensing of new forces at 6 micron separation