Wavelength dependence of optical tweezer trapping forces on dye-doped polystyrene microspheres

Kendrick, M. J.; McIntyre, David; Ostroverkhova, Oksana

doi:10.1364/josab.26.002189

Cited by 22 publications

(27 citation statements)

References 35 publications

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“…Previously, optical forces and their relationship to optical resonances have been studied in an optical levitation scheme over short laser wavelength ranges 20 and for dye-loaded dielectric particles. 21 In the first case, since the particles were not actually optically trapped, only the scattering force and not the gradient force was considered. In the second case, the trap strength measurements were normalized by beads lacking dye, meaning that only the absorption resonance, and not the total extinction resonance, was considered.…”

Section: Introductionmentioning

confidence: 99%

Tunable optical tweezers for wavelength-dependent measurements

Hester

Campbell

López-Mariscal

et al. 2012

Review of Scientific Instruments

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Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them.

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Section: Introductionmentioning

confidence: 99%

Tunable optical tweezers for wavelength-dependent measurements

Hester

Campbell

López-Mariscal

et al. 2012

Review of Scientific Instruments

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“…Another possibility is to use a point-matching method to determine the expansion coefficients of the incident fields, e.g. Kendrick et al [166] and Section 6.6.…”

Section: Use Of Ebcm For Arbitrary Shaped Beamsmentioning

confidence: 99%

On the electromagnetic scattering of arbitrary shaped beams by arbitrary shaped particles: A review

Gouesbet

Lock

2015

Journal of Quantitative Spectroscopy and Radiative Transfer

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“…To this end, we assessed how the real and the imaginary parts of the polarizability vary with the optical frequency according to the classical model of electron oscillation in a way similar to that reported by Kendrick and coworkers. 18 As illustrated in Fig. 6, the imaginary part is a Lorentzian centered at the maximum of the absorption spectrum (black curve) whereas the real part exhibits a dispersive prole that crosses zero at the maximum of the absorption spectrum (red curve).…”

mentioning

confidence: 97%

“…Accordingly, the optical force exerting on the object at the laser focus should depend also on the frequency of the optical eld. 17,18 This spectral dependence of the optical force is …”

mentioning

confidence: 99%

“…As the polarizability of a sphere is proportional to the volume of the sphere (eqn (2)), the scattering force is small in comparison with the gradient force when considering small Rayleigh particles. 18 In general, the imaginary part of the polarizability might contribute additional terms to the scattering force. However, as the scattering force scales with the squared polarizability (and hence the squared volume), we argue that the contribution to the scattering force from the imaginary polarizability is also small relative to the gradient force as long as the particle is in the Rayleigh regime regardless Fig.…”

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Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

et al. 2017

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Despite a tremendous success in the optical manipulation of microscopic particles, it remains a challenge to manipulate nanoparticles especially as the polarizability of the particles is small. With a picosecond-pulsed near-infrared laser, we demonstrated recently that the confinement of dye-doped polystyrene nanobeads is significantly enhanced relative to bare nanobeads of the same dimension. We attributed the enhancement to an additional term of the refractive index, which results from two-photon resonance between the dopant and the optical field. The optical confinement is profoundly enhanced as the half-wavelength of the laser falls either on the red side, or slightly away from the blue side, of the absorption band of the dopant. In contrast, the ability to confine the nanobeads is significantly diminished as the half-wavelength of the laser locates either at the peak, or on the blue side, of the absorption band. We suggest that the dispersively shaped polarizability of the dopant near the resonance is responsible to the distinctive spectral dependence of the optical confinement of nanobeads. This work advances our understanding of the underlying mechanism of the enhanced optical confinement of doped nanoparticles with a nearinfrared pulsed laser, and might facilitate future research that benefits from effective sorting of selected nanoparticles beyond the limitations of previous approaches. IntroductionOptical trapping of microscopic objects with a focused continuous wave (cw) laser beam is a mainstream tool to manipulate microscopic particles in solutions. Despite its widespread applications in physical, 1,2 materials, 3 and life 4-6 sciences, effective trapping of particles in the nanometre scale has been demonstrated only with limited success. 7,8In comparison with metallic nanoparticles comprising gold 9,10 or silver 11,12 the polarizability of dielectric nanoparticles of a comparable dimension is much smaller. As a result, optical manipulation of dielectric nanoparticles remains challenging. 13Towards this end, numerous strategies have been attempted aiming either to decrease the pushing (scattering, absorption and temporal) force, or to increase the trapping (gradient) force.14-19 For instance, a near-infrared (NIR) pulsed laser was employed as a trapping laser to minimize the scattering and absorption forces; 14 the temporal force was further decreased with a laser of a long pulse-width.15 On the other hand, the trapping force can be increased by maximizing the gradient of the optical eld; this is achieved mainly by (i) using a high numerical-aperture (NA) objective lens, (ii) creating a large optical eld in the near eld, 14 or (iii) utilizing the intense optical eld associated with a ultrashort pulsed laser. 16Distinct from these approaches, it is possible to boost the gradient force by increasing the real part of the polarizability through optical resonance. This idea has been demonstrated on trapping doped dielectric nanoparticles, whose effective polarizability is increased as a result of opt...

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Wavelength dependence of optical tweezer trapping forces on dye-doped polystyrene microspheres

Cited by 22 publications

References 35 publications

Tunable optical tweezers for wavelength-dependent measurements

Tunable optical tweezers for wavelength-dependent measurements

On the electromagnetic scattering of arbitrary shaped beams by arbitrary shaped particles: A review

Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

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