Non-conservative instabilities in optical vacuum traps

V. Svak, Y. Arita, S. H. Simpson, O. Brzobohatý, M. Šiler, P. Jákl, J. Kanka, P. Zemánek, K. Dholakia

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Particles held in optical tweezers are commonly thought to be at thermodynamic equilibrium with their environment. Under this assumption the elastic energy of the trap is equal to the thermal energy. As a result the variance of the particle position is completely independent of viscosity and inversely proportional to the optical power in the trap. Here we show that these conditions only hold for very high symmetry cases e.g. perfectly spherical particles in unaberrated, linearly polarized Gaussian traps. Here we show that any reduction in symmetry leads to asymmetrically coupled degrees of freedom. The associated force field is linearly non-conservative and the tweezer is no longer at equilibrium. In overdamped systems the effect is a underlying systematic bias to the Brownian motion. In underdamped systems, this systematic component can accumulate momentum, eventually destabilizing the trap. We illustrate this latter effect with reference to two systems, (i) an isotropic sphere in a circularly polarized trap, and (ii) a birefringent sphere in a linearly polarized trap. In both cases the instability can be approached either by decreasing air pressure or by increasing optical power. Close to instability, the trapped particle executes increasingly coherent motion that is highly sensitive to external perturbations. Potential applications to weak force sensing are discussed.

Original languageEnglish
Title of host publicationComplex Light and Optical Forces XIV
EditorsDavid L. Andrews, Enrique J. Galvez, Halina Rubinsztein-Dunlop
PublisherSPIE
ISBN (Electronic)9781510633575
DOIs
Publication statusPublished - 2020 Jan 1
EventComplex Light and Optical Forces XIV 2020 - San Francisco, United States
Duration: 2020 Feb 42020 Feb 5

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11297
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceComplex Light and Optical Forces XIV 2020
CountryUnited States
CitySan Francisco
Period20/2/420/2/5

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

Fingerprint Dive into the research topics of 'Non-conservative instabilities in optical vacuum traps'. Together they form a unique fingerprint.

  • Cite this

    Svak, V., Arita, Y., Simpson, S. H., Brzobohatý, O., Šiler, M., Jákl, P., Kanka, J., Zemánek, P., & Dholakia, K. (2020). Non-conservative instabilities in optical vacuum traps. In D. L. Andrews, E. J. Galvez, & H. Rubinsztein-Dunlop (Eds.), Complex Light and Optical Forces XIV [112970F] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 11297). SPIE. https://doi.org/10.1117/12.2545948