Nonconservative dynamics of optically trapped high-aspect-ratio nanowires

Toe, Wen Jun; Ortega-Piwonka, Ignacio; Angstmann, Christopher N.; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati; Henry, Bryan R.; Reece, Peter J.

doi:10.1103/physreve.93.022137

Cited by 14 publications

(19 citation statements)

References 22 publications

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“…4) due to the optical torque and show small angular thermal fluctuations about their stability axis 510 that can be measured together with optical aligning torques [20,104]. Moreover, the translation-rotation coupling in non-spherical particles can yield regular biased orbital motion that has been the subject of recent experimental and theoretical investigations [107,113,114,115,116]. [118,119,120]:…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Optical tweezers and their applications

Polimeno

Magazzù

Iatí

et al. 2018

Journal of Quantitative Spectroscopy and Radiative Transfer

198

147

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Section: Accepted Manuscriptmentioning

confidence: 99%

Optical tweezers and their applications

Polimeno

Magazzù

Iatí

et al. 2018

Journal of Quantitative Spectroscopy and Radiative Transfer

198

147

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“…[5,6]. More recent work shows that the optical forces are locally conservative in this particular system, for reasons of symmetry rather than any more fundamental requirement [7][8][9][10][11][12] and, furthermore, that the nonconservative character of optical forces manifests itself whenever the symmetry of the system is lowered or when the particle roams widely in a weak trap [13,14]. In the overdamped regime, this results in persistent probability currents connected with a subtle, systematic bias in the Brownian motion of the trapped object [15].…”

Section: Introductionmentioning

confidence: 91%

“…As described previously [17], C can be evaluated directly from Eqs. ( 9) and (10). The process can be summarized as follows.…”

Section: A Linearized Forcesmentioning

confidence: 99%

Stochastic Hopf bifurcations in vacuum optical tweezers

et al. 2021

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The forces acting on an isotropic microsphere in optical tweezers are effectively conservative. However, reductions in the symmetry of the particle or trapping field can break this condition. Here we theoretically analyze the motion of a particle in a linearly nonconservative optical vacuum trap, concentrating on the case where symmetry is broken by optical birefringence, causing nonconservative coupling between rotational and translational degrees of freedom. Neglecting thermal fluctuations, we first show that the underlying deterministic motion can exhibit a Hopf bifurcation in which the trapping point destabilizes and limit cycles emerge whose amplitude grows with decreasing viscosity. When fluctuations are included, the bifurcation of the underlying deterministic system is expressed as a transition in the statistical description of the motion. For high viscosities, the probability distribution is normal, with a kurtosis of three, and persistent probability currents swirl around the stable trapping point. As the bifurcation is approached, the distribution and currents spread out in phase space. Following the bifurcation, the probability distribution function hollows out, reflecting the underlying limit cycle, and the kurtosis halves abruptly. The system is seen to be a noisy self-sustained oscillator featuring a highly uneven limit cycle. A variety of applications, from autonomous stochastic resonance to synchronization, is discussed.

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“…These effects have been described theoretically and measured experimentally. 6,9,10 In the underdamped regime linear non-conservatism has a more dramatic effect. 11 In particular, quasi-periodic paths that increase the energy of the particle accumulate momentum and grow in amplitude while ones that lose energy are suppressed.…”

Section: Introductionmentioning

confidence: 99%

Non-conservative instabilities in optical vacuum traps

Svak¹,

Arita

Simpson³

et al. 2020

Complex Light and Optical Forces XIV

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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.

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Nonconservative dynamics of optically trapped high-aspect-ratio nanowires

Cited by 14 publications

References 22 publications

Optical tweezers and their applications

Optical tweezers and their applications

Stochastic Hopf bifurcations in vacuum optical tweezers

Non-conservative instabilities in optical vacuum traps

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