Scattering from Model Nonspherical Particles

Borghese, Ferdinando; Denti, P.; Saija, Rosalba

doi:10.1007/978-3-662-05330-0

Cited by 85 publications

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“…Then we use an approach based on the Transition (T-)Matrix formalism [18], to calculate the optical force and torque applied to the trapped object, of arbitrary size and symmetry, which is being modelled as an aggregate of spheres with size below the radiation wavelength. In the specific case of polymer nanofibers we calculate the radiation force ( rad Dealing with quantitative comparisons between theory and experiments, a crucial issue to be addressed is the hydrodynamics of the trapped particle.…”

Section: Introductionmentioning

confidence: 99%

“…Our starting point is the calculation of the field configuration in the focal region of a high numerical aperture (NA) objective lens in absence of particles [15]. Once the field is known, the radiation force and torque exerted on a trapped particle is calculated by resorting to momentum conservation for the combined system of field and particle.Then we use an approach based on the Transition (T-)Matrix formalism [18], to calculate the optical force and torque applied to the trapped object, of arbitrary size and symmetry, which is being modelled as an aggregate of spheres with size below the radiation wavelength. In the specific case of polymer nanofibers we calculate the radiation force ( rad Dealing with quantitative comparisons between theory and experiments, a crucial issue to be addressed is the hydrodynamics of the trapped particle.…”

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Rotational dynamics of optically trapped nanofibers

et al. 2010

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The optical trapping of polymeric nanofibers and the characterization of the rotational dynamics are reported. A strategy to apply a torque to a polymer nanofiber, by tilting the trapped fibers using a symmetrical linear polarized Gaussian beam is demonstrated. Rotation frequencies up to 10 Hz are measured, depending on the trapping power, the fiber length and the tilt angle. A comparison of the experimental rotation frequencies in the different trapping configurations with calculations based on optical trapping and rotation of linear nanostructures through a T-Matrix formalism, accurately reproduce the measured data, providing a comprehensive description of the trapping and rotation dynamics.PACS numbers: 87.80.Cc; 45.20.da; 42.50.Wk; 07.10.Pz * Corresponding author: antonio.neves@unisalento.it † marago@its.me.cnr.it 2 Optical forces are currently employed to study a range of chemical, physical and biological problems, by trapping microscale objects and measuring sub pico-Newton forces [1,2]. In particular, optical trapping of elongated nanoparticles, including nanowires [3] and nanotubes [4], is gaining an increasing interest because of the high shape anisotropy and unique physical properties of these systems. Among linear nanostructures, polymeric nanofibers are novel nanomaterials with many strategic applications ranging from scaffolding for tissue-engineering to integrated photonics [5,6] and electronics [7,8]. However, optical trapping and manipulation of polymer nanofibers has never been reported, despite the understanding of the optical forces and torques acting on these objects as well as their trapping dynamics might open a new range of applications, exploiting the polymeric fibers as local probes or active elements in microrheology [9] and microfluidics [10], and in next generation Photonic Force Microscopy [3]. Furthermore, the nanofibers are characterized by subwavelength diameters and lengths in the range 10-100 m, therefore constituting ideal systems for studying effects occurring in the intermediate regime between the Rayleigh scattering and geometrical optics.A laser beam can carry intrinsic (spin) or extrinsic (orbital) angular momentum, associated to the polarization and to the light beam phase structure, respectively [11]. Either trapping beams with elliptical polarization or with a rotating linear polarization can be exploited to apply a torque to trapped objects. Rotation in trapped particles can also be induced by exploiting the phase structure or the astigmatism of the trapping laser beam [12 and references therein]. The rotatable object can be spherical, exhibiting a birefringence or a slight absorption, or it can have more complex shapes, as in microfabricated propellers by two-photon polymerization [13] or cylinders with inclined faces [14].In this work we trap polymeric nanofibers and characterize their rotational dynamics in different trapping configurations by a different method. We employ a strategy to rotate a dielectric cylinder with flat end faces, based on a non-rotat...

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Section: Introductionmentioning

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Rotational dynamics of optically trapped nanofibers

et al. 2010

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“…The problem of wave scattering by particles is one of the fundamental subjects in physics, with a very long history, and we can find quite a long list of articles dealing with it [1][2][3][4][5][6][7][8]. The articles can be divided by subject into two classes: single scattering and multiple scattering.…”

Section: Introductionmentioning

confidence: 99%

General Theory of Wave Scattering by Two Separated Particles

Park¹,

Myung-Whun²,

Kim³

2014

Journal of the Optical Society of Korea

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A general theory of scalar wave scattering by two separated particles is developed to give the coefficients of scattering and transmission in the form of recurrence formulae. Iterative applications of the formulae yield the coefficients in the form of power series of the coefficients obtained from single-particle scattering theories, and each term of the of power series can be interpreted as multiple scattering of the wave between the two particles in increasingly higher order.

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“…Due to this, the field of light scattering by cosmic dust has always been at the frontier of the study of interaction of electromagnetic waves with non-spherical and inhomogeneous particles. It has inspired publication of the scholarly books by van de Hulst (1957), Schuerman (1980), Kokhanovsky (2001), Hovenier et al (2004), Voshchinnikov (2004), Borghese et al (2010), and Mishchenko et al (2000Mishchenko et al ( , 2002Mishchenko et al ( , 2010 and numerous book chapters, e.g., Mukai (1989), Lien (1991), Gustafson (1999), Gustafson et al (2001), Kolokolova et al (2004a, b). To consider the scattering of electromagnetic waves by an object of complex structure, we will determine this object as a configuration of discrete finite constituents.…”

Section: Introductionmentioning

confidence: 99%