scholarly journals Quantitative Study of Conservative Gradient Force and Non-conservative Scattering Force in Optical Tweezers

2021 ◽  
Author(s):  
Xiao Li ◽  
Hongxia Zheng ◽  
Chi Hong Yuen ◽  
Junjie Du ◽  
Jun Chen ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Quantitative Study ◽  
Gradient Force ◽  
Scattering Force

Optical Tweezers: A Practical Guide

1995 ◽  
Vol 1 (2) ◽  
pp. 65-74
Author(s):  
Scot C. Kuo
Keyword(s):  
Optical Tweezers ◽  
Optical Microscope ◽  
Gradient Force ◽  
Biological Applications ◽  
Single Beam ◽  
Practical Guide ◽  
Microscopy Techniques ◽  
Displacement Measurements

Optical tweezers, or the single-beam optical gradient force trap, is becoming a major tool in biology for noninvasive micromanipulation on an optical microscope. The principles and practical aspects that influence construction are presented in an introductory primer. Quantitative theories are also reviewed but have yet to supplant user calibration. Various biological applications are summarized, including recent quantitative force and displacement measurements. Finally, tantalizing developments for new, nonimaging microscopy techniques based on optical tweezers are included.

TRAPPING OF GOLD NANOPARTICLE AND POLYSTYRENE BEADS BY DYNAMIC OPTICAL TWEEZERS

2015 ◽  
Vol 74 (8) ◽  
Author(s):  
M. S. Aziz ◽  
K. Tufail ◽  
N. E. Khamsan ◽  
S. Affandi ◽  
S. Daud ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Dark Soliton ◽  
Input Power ◽  
Optical Force ◽  
Gradient Force ◽  
Polystyrene Beads ◽  
Multiple Trapping ◽  
Different Diameters ◽  
20 Nm ◽  
Good Agreement

Gold nanoparticles and polystyrene beads are very important to use in advanced nanoscopic optical trapping techniques to probe any biological system of interest. Multiple trapping of these particles with different diameters can be performed by an optical tweezers system employing dark soliton controlled by Gaussian pulse within a particular configuration of microring resonators. By controlling some parameters and input power of the system, dynamics of the tweezers can be tuned. Radiation pressure acting on the particles including gradient and scattering forces were theoretically measured as a function of normalized position from the center of the laser beam. In this work, the highest output signal in the form of potential well is recorded at 112.80 W corresponding to 1.6 mm wavelength. Sizes of the tweezers are found within the range of 20 nm and the highest value of the optical force is recorded at 895.70 pN. We have demonstrated that the gradient force component is dominant over particle size within Rayleigh regime, thus a good agreement with theory is found.

scholarly journals Laser Self-Trapping in Optical Tweezers for Nonlinear Particles

2021 ◽  
Author(s):  
Quy Quang Ho ◽  
Thanh Doan Thai ◽  
Kien Xuan Bui ◽  
Thang Manh Nguyen
Keyword(s):  
Laser Beam ◽  
Optical Tweezers ◽  
Kerr Effect ◽  
Mass Density ◽  
The Self ◽  
Kerr Medium ◽  
Gradient Force ◽  
Trapping Region ◽  
Self Trapping ◽  
Particle Solution

Abstract The optical tweezers are used to trap the particles embedded in a suitable fluid. The optical trap efficiency is significantly enhanced for nonlinear particleswhich response to the Kerr effect. The optical transverse gradient force makes these particles’ mass density in trapping region increasing, and the Kerr medium can be created. When the laser Gaussian beam propagates through it, the self-focusing, and consequentlyself-trappingcan appear. In this paper, a model describing the laser self-trapping in nonlinear particle solution of optical tweezers is proposed. The expressions for the Kerr effect, effective refractive index of nonlinear particle solution and the intensity distribution of reshaped Gaussian laser beam are derived, and the self-trapping of laser beam is numerically investigated. Finally, the guide properties of nonlinear particles-filled trapping region and guiding condition are analysed and discussed.

Optical tweezers as a tool to study cellular function

1992 ◽  
Vol 50 (1) ◽  
pp. 424-425
Author(s):  
Steven M. Block
Keyword(s):  
Optical Tweezers ◽  
Optical Trap ◽  
Three Dimensional ◽  
Characteristic Size ◽  
Gradient Force ◽  
Single Beam ◽  
Temporal Precision ◽  
Dielectric Particles ◽  
Ligand Interactions ◽  
20 Nm

A single beam gradient force optical trap1-3, or “optical tweezers”, exerts forces on microscopic dielectric particles using a highly focused beam of laser light, and can achieve stable, three-dimensional trapping of such particles (for a review, see ref. 4). Using an infrared laser, calibratable forces in the piconewton (pN) range can be easily generated without causing significant damage to living biological specimens. Optical tweezers work through the microscope, without mechanical intrusion within sealed preparations, and can even reach directly inside transparent cells or organelles. Because it is formed by light, an optical trap can be controlled with very high spatial and temporal precision. Its characteristic size (i.e., its “grasp”) is approximately equal to the wavelength of light, but it can be used to capture and/or manipulate objects ranging in size from ∼20 nm to ∼100 mm. Biological preparations (e.g., cells, vesicles, organelles) or small particles (e.g., latex or silica microspheres, perhaps carrying reagents coupled to their surfaces) can be held, maneuvered, or released at will. Already, researchers have begun to contemplate experiments that were practically impossible just a few years ago. Some possibilities include: (1) the sorting and isolation of cells, vesicles, organelles, chromosomes, etc.; (2) the direct measurement of the mechanical properties of cytoskeletal assemblies, membranes, or membrane-bound elements; (3) measurement of the tiny forces produced by mechanoenzymes; (4) establishing cell-cell contacts, or measuring receptor-ligand interactions; (5) studying cellular rheology on the micrometer scale; (6) doing cellular microsurgery, membrane fusion, and building novel cellular (or noncellular) structures; (7) capturing and maintaining fragile biological structures away from vessel surfaces, in order to study them in isolation under optimal viewing conditions; (8) and much more! The principles by which optical tweezers work will be explained, and a videotape illustrating a number of experimental uses will be shown.

scholarly journals Formation of the reverse flow of energy in a sharp focus

2019 ◽  
Vol 43 (5) ◽  
pp. 714-722
Author(s):  
V.V. Kotlyar ◽  
S.S. Stafeev ◽  
A.G. Nalimov ◽  
A.A. Kovalev
Keyword(s):  
Interference Pattern ◽  
Opposite Direction ◽  
Wave Vector ◽  
Optical Axis ◽  
Reverse Flow ◽  
Plane Waves ◽  
Gradient Force ◽  
Sharp Focusing ◽  
Scattering Force ◽  
The Right

It was theoretically shown that in the interference pattern of four plane waves with specially selected directions of linear polarization it is formed a reverse flow of energy. The areas of direct and reverse flow alternate in a staggered order in the cross section of the interference pattern. The absolute value of the reverse flow directly depends on the angle of convergence of the plane waves (on the angle between the wave vector and the optical axis) and reach the maximum at an angle of convergence close to 90 degrees. The right-handed triples of the vectors of four plane waves (the wave vector with positive values of projection to optical axis and the vector of electric and magnetic fields) when added in certain areas of the interference pattern form an electromagnetic field described by the left-handed triple of vectors; however, the projection of wave vector to optical axis has negative values. In these areas, the light propagates in the opposite direction. A similar explanation of the mechanism of the formation of a reverse flow can be applied to the case of a sharp focusing of a laser beam with a second-order polarization singularity. It is also shown that if a spherical dielectric Rayleigh nanoparticle is placed in the backflow region, then a force directed in the opposite direction will act on it (the scattering force will be more than the gradient force).

Trapping of resonant metallic nanoparticles with engineered vectorial optical field

Nanophotonics ◽  
2014 ◽  
Vol 3 (6) ◽  
pp. 351-361 ◽  
Author(s):  
Guanghao Rui ◽  
Qiwen Zhan
Keyword(s):  
Optical Tweezers ◽  
Metallic Nanoparticles ◽  
Three Dimensional ◽  
Optical Field ◽  
Physical Sciences ◽  
Resonant Condition ◽  
Optical Heating ◽  
Scattering Force ◽  
Novel Strategy ◽  
Strong Scattering

AbstractOptical trapping and manipulation using focused laser beams has emerged as a powerful tool in the biological and physical sciences. However, scaling this technique to metallic nanoparticles remains challenging due to the strong scattering force and optical heating effect. In this work, we propose a novel strategy to optically trap metallic nanoparticles even under the resonant condition using engineered optical field. The distribution of the optical forces can be tailored through optimizing the spatial distribution of a vectorial optical illumination to favour the stable trapping of a variety of metallic nanoparticles under various conditions. It is shown that this optical tweezers has the ability of generating negative scattering force and supporting stable three-dimensional trapping for gold nanoparticles at resonance while avoiding trap destabilization due to optical overheating. The technique presented in this work offers a versatile solution for trapping metallic nanoparticles and may open up new avenues for optical manipulation.

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