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Optical trapping of the low index of refraction particles by focused vortex beams and two face-to-face focused beams

Duan Meiling, Zhang Hanghang, Li Jinhong

Optica Applicata

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2020

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Vol. 50, nr 3

447--461

EN

Using the extended Huygens–Fresnel principle and Rayleigh scattering theory, optical trapping of the low index of refraction particles using a focused Gaussian Schell-model (GSM) non-vortex beam, a focused GSM vortex beam, and two face-to-face focused GSM vortex beams have been studied. The results demonstrate that the focused GSM non-vortex beam cannot capture the low index of refraction particles, however, the focused GSM vortex beam can be a two-dimensional trap of particles in the z-axis, and the transverse gradient force Fgrad,x and the trapping equilibrium region increase as the topological charge m increases. As the focal length f or the refractive index of particles np decreases, the radiation forces increase and the trapping ability also enhances. To trap the low index particles in three-dimensional space, we adopt that the two face-to-face focused GSM vortex beams can be used to construct an optical potential well. The transverse gradient force of two face-to-face focused GSM vortex beams is twice that of a single GSM vortex beam. The limit of the radius for the low index of refraction particles that were stably captured has also been determined. The obtained results provide valuable information for trapping and manipulating the low index of refraction particles using GSM vortex beams, which may be applied in micromanipulation, biotechnology, nanotechnology and so on.

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Near-field multiple optical trapping using high order axially symmetric polarized beams

Zhou Z, Tan Q, Zhu L, Yang C

Optica Applicata

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2013

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Vol. 43, nr 2

s. 287--296

EN

The near-field multiple optical trapping using high order axially symmetric polarized beams (ASPBs) is studied for the first time. First, a near-field optical trapping scheme is proposed based on the Kretschmann–Raether configuration, and surface plasmon polaritons (SPPs) field distributions excited by incident ASPBs are calculated, which present a multi-focal-spot pattern and the size of spots is much smaller than that of the diffraction limitation. Then, the gradient forces on Rayleigh dielectric particles formed by the multi-focal-spot focused field are computed, which indicates that multiple ultra-small particles with the refractive index higher than that of the ambient medium can be trapped simultaneously on the metal surface. The number and size of trapped particles can be manipulated by flexibly modifying the polarization order of incident beams, which is expected to enhance the capability of traditional optical trapping systems and provide a solution for massively parallel optical trapping of nanometer-sized particles.

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Pęseta optyczna jako narzędzie współczesnej bioinżynierii

Bacia M., Drobczyński S., Masajada J., Kopaczyńska M.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2013

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Vol. 19, nr 3

114-122

PL

Pęseta optyczna jest dość nowym narzędziem pozwalającym na wszechstronną manipulację obiektami w mikro- i nanoskali. Manipulacja odbywa się wewnątrz odpowiednio ukształtowanej zogniskowanej wiązki laserowej. Wykorzystując technikę holograficzną, można za pomocą pęsety optycznej utworzyć kilkanaście niezależnych pułapek optycznych, zdolnych do chwytania mikroobiektów. Urządzenie to wykorzystuje się między innymi do pomiaru sił z rozdzielczością pojedynczych pikoniutonów, segregacji komórek, pomiaru właściwości mechanicznych błon komórkowych, nici DNA lub do badania procesów biochemicznych na poziomie komórkowym. W niniejszej pracy przedstawiano krótki opis techniczny zbudowanych w zespole układów, jak również omówiono przykładowe zastosowania pęsety optycznej.

EN

Optical tweezers are a quite new tool for versatile manipulation of objects in micro and nanoscale. Optical tweezers may be used in various fields, for example in microbiology. The observation and measurement take place inside the specially focused laser beam. The holographic methods enables generating several optical traps that can be driven, independently. The possible applications include the force measurement between molecules and cells (at the level of piconewtons), cells segregation and transport, cells activity analysis, DNA mechanical properties analysis and many others. In this paper, short technical data on the systems constructed in our group, along with the description of potential applications, are presented.