Vinoth Balasubramani; Anand Vijayakumar; Mani Ratnam Rai; Joseph Rosen; Chau-Jern Cheng; Oleg V. Minin; Igor V. Minin
We introduce a novel phase-only diffractive optical element called chiral binary square axicon (CBSA). The CBSA is designed by linearly rotating the square half-period zones of the binary square axicon with respect to one another. A quadratic phase mask (QPM) is combined with the CBSA using modulo-2π phase addition technique to bring the far-field intensity pattern of CBSA at the focal plane of the QPM and to introduce quasiachromatic effects. The periodically rotated zones of CBSA produce a whirlpool phase profile and twisted intensity patterns at the focal plane of QPM. The degree of twisting seen in the intensity patterns is dependent upon the angular step size of rotation of the zones. The intensity pattern was found to rotate around the optical axis along the direction of propagation. The phase patterns of CBSA with different angles of zone rotation are displayed on a phase-only spatial light modulator, and the experimental results were found to match with the simulation results. To evaluate the optical trapping capabilities of CBSA, an optical trapping experiment was carried out and the optical fields generated by CBSA were used for trapping and rotating yeast cells.
DOI
Showing posts with label Optical Engineering. Show all posts
Showing posts with label Optical Engineering. Show all posts
Wednesday, December 11, 2019
Tuesday, May 21, 2019
Designing the measurement of the atomic mass density wave of a Gaussian mass-polariton pulse in optical fibers
Mikko Partanen, Jukka Tulkki
We have recently introduced the mass-polariton (MP) theory of light to describe the coupled dynamics of the field and matter when a light pulse propagates in a transparent medium. The theory is based on combining the electrodynamics of continuous media and continuum mechanics, which are both widely used standard theories in their fields of physics. The MP theory shows that a light pulse propagating in a transparent medium is accompanied by a mass density wave (MDW) of atoms set in motion by the optical force density of the light pulse. In the corresponding quantum picture, the covariant coupled state of the field and matter is described as the MP quasiparticle, which has coupled field and medium components. We study a schematic experimental setup that would enable measurements of the atomic displacements and the excess mass density related to the MDW of a Gaussian MP pulse propagating in an optical fiber made of fused silica.
DOI
We have recently introduced the mass-polariton (MP) theory of light to describe the coupled dynamics of the field and matter when a light pulse propagates in a transparent medium. The theory is based on combining the electrodynamics of continuous media and continuum mechanics, which are both widely used standard theories in their fields of physics. The MP theory shows that a light pulse propagating in a transparent medium is accompanied by a mass density wave (MDW) of atoms set in motion by the optical force density of the light pulse. In the corresponding quantum picture, the covariant coupled state of the field and matter is described as the MP quasiparticle, which has coupled field and medium components. We study a schematic experimental setup that would enable measurements of the atomic displacements and the excess mass density related to the MDW of a Gaussian MP pulse propagating in an optical fiber made of fused silica.
DOI
Monday, August 27, 2018
Plasmonic response of graphene-like metallic-molecular nanocluster for optical applications
Aydin Amini; Saeed Golmohammadi; Sina Aghili
Three periodic structures based on arrays of graphene-like nanocluster have been proposed and their plasmonic response has been investigated. In the first step, plasmonic response of each periodic structure has been investigated using the hybridization diagram for a proposed single unit cell. In the second step, according to obtained results, appropriate applications for each structure have been introduced. The study is divided into three sections. In the first section, we have considered a periodic array of triangular-shaped nanoparticles to form a graphene-like nanocluster. This configuration shows considerable capabilities to act as a nanoscale waveguide. Alternatively, in the second section, we have replaced triangular nanoparticles with nanospheres. Results of this configuration show considerable enhancements in optical forces and hence, represent it as an acceptable candidate for tweezing and optical manipulations. Finally, we have replaced nanospheres with ring nanoparticles in each node of such a similar nanocluster. This change leads to create states of plasmonic resonances in spectral response, which is sensitive to surrounding medium and can be used as a sensing tool to detect medium perturbations.
DOI
Three periodic structures based on arrays of graphene-like nanocluster have been proposed and their plasmonic response has been investigated. In the first step, plasmonic response of each periodic structure has been investigated using the hybridization diagram for a proposed single unit cell. In the second step, according to obtained results, appropriate applications for each structure have been introduced. The study is divided into three sections. In the first section, we have considered a periodic array of triangular-shaped nanoparticles to form a graphene-like nanocluster. This configuration shows considerable capabilities to act as a nanoscale waveguide. Alternatively, in the second section, we have replaced triangular nanoparticles with nanospheres. Results of this configuration show considerable enhancements in optical forces and hence, represent it as an acceptable candidate for tweezing and optical manipulations. Finally, we have replaced nanospheres with ring nanoparticles in each node of such a similar nanocluster. This change leads to create states of plasmonic resonances in spectral response, which is sensitive to surrounding medium and can be used as a sensing tool to detect medium perturbations.
DOI
Friday, July 27, 2018
Estimation of thermocapillary force during laser trapping of confined microbubbles in a liquid
Ujitha Abeywickrema; Chenglong Zhao; Partha Banerjee
A theoretical model is introduced to determine the thermocapillary force acting on a microbubble, which adheres to the wall of a container filled with a liquid, during trapping using a focused continuous-wave (CW) laser beam. The model is developed by considering all possible forces acting on the microbubble, which also includes the optical force, the viscous force, and the friction force. The thermocapillary force, estimated from the relative velocity of the trapped microbubble with respect to the container, compares favorably with theoretical predictions based on the temperature gradient induced by the focused laser beam. The proposed experiment can be also used to determine the contact angle and/or the coefficient of friction of the microbubble at the microbubble–container interface. Our results should be useful in the design of efficient systems using microbubbles for drug delivery and water treatment systems.
DOI
A theoretical model is introduced to determine the thermocapillary force acting on a microbubble, which adheres to the wall of a container filled with a liquid, during trapping using a focused continuous-wave (CW) laser beam. The model is developed by considering all possible forces acting on the microbubble, which also includes the optical force, the viscous force, and the friction force. The thermocapillary force, estimated from the relative velocity of the trapped microbubble with respect to the container, compares favorably with theoretical predictions based on the temperature gradient induced by the focused laser beam. The proposed experiment can be also used to determine the contact angle and/or the coefficient of friction of the microbubble at the microbubble–container interface. Our results should be useful in the design of efficient systems using microbubbles for drug delivery and water treatment systems.
DOI
Friday, April 27, 2018
Rotation of an optically trapped vaterite microsphere measured using rotational Doppler effect
Xinlin Chen; Guangzong Xiao; Wei Xiong; Kaiyong Yang; Hui Luo; Baoli Yao
The angular velocity of a vaterite microsphere spinning in the optical trap is measured using rotational Doppler effect. The perfectly spherical vaterite microspheres are synthesized via coprecipitation in the presence of silk fibroin nanospheres. When trapped by a circularly polarized beam, the vaterite microsphere is uniformly rotated in the trap center. The probe beams containing two Laguerre–Gaussian beams of opposite topological charge l = ± 7, l = ± 8, and l = ± 9 are illuminated on the spinning vaterite. By analyzing the backscattered light, a frequency shift is observed scaling with the rotation rate of the vaterite microsphere. The multiplicative enhancement of the frequency shift proportion to the topological charge has greatly improved the measurement precision. The reliability and practicability of this approach are verified through varying the topological charge of the probe beam and the trapping laser power. In consideration of the excellent measurement precision of the rotation frequency, this technique might be generally applicable in studying the torsional properties of micro-objects.
DOI
The angular velocity of a vaterite microsphere spinning in the optical trap is measured using rotational Doppler effect. The perfectly spherical vaterite microspheres are synthesized via coprecipitation in the presence of silk fibroin nanospheres. When trapped by a circularly polarized beam, the vaterite microsphere is uniformly rotated in the trap center. The probe beams containing two Laguerre–Gaussian beams of opposite topological charge l = ± 7, l = ± 8, and l = ± 9 are illuminated on the spinning vaterite. By analyzing the backscattered light, a frequency shift is observed scaling with the rotation rate of the vaterite microsphere. The multiplicative enhancement of the frequency shift proportion to the topological charge has greatly improved the measurement precision. The reliability and practicability of this approach are verified through varying the topological charge of the probe beam and the trapping laser power. In consideration of the excellent measurement precision of the rotation frequency, this technique might be generally applicable in studying the torsional properties of micro-objects.
DOI
Friday, February 2, 2018
Geometrical effect characterization of femtosecond-laser manufactured glass microfluidic chips based on optical manipulation of submicroparticles
Domna G. Kotsifaki; Mark D. Mackenzie; Georgia Polydefki; Ajoy K. Kar; Mersini Makropoulou; Alexandros A. Serafetinides
Microfluidic devices provide a platform with wide ranging applications from environmental monitoring to disease diagnosis. They offer substantive advantages but are often not optimized or designed to be used by nonexpert researchers. Microchannels of a microanalysis platform and their geometrical characterization are of eminent importance when designing such devices. We present a method that is used to optimize each microchannel within a device using high-throughput particle manipulation. For this purpose, glass-based microfluidic devices, with three-dimensional channel networks of several geometrical sizes, were fabricated by employing laser fabrication techniques. The effect of channel geometry was investigated by employing an optical tweezer. The optical trapping force depends on the flow velocity that is associated with the dimensions of the microchannel. We observe a linear dependence of the trapping efficiency and of the fluid flow velocity, with the channel dimensions. We determined that the highest trapping efficiency was achieved for microchannels with aspect ratio equal to one. Numerical simulation validated the impact of the device design dimensions on the trapping efficiency. This investigation indicates that the geometrical characteristics, the flow velocity, and trapping efficiency are crucial and should be considered when fabricating microfluidic devices for cell studies.
DOI
Microfluidic devices provide a platform with wide ranging applications from environmental monitoring to disease diagnosis. They offer substantive advantages but are often not optimized or designed to be used by nonexpert researchers. Microchannels of a microanalysis platform and their geometrical characterization are of eminent importance when designing such devices. We present a method that is used to optimize each microchannel within a device using high-throughput particle manipulation. For this purpose, glass-based microfluidic devices, with three-dimensional channel networks of several geometrical sizes, were fabricated by employing laser fabrication techniques. The effect of channel geometry was investigated by employing an optical tweezer. The optical trapping force depends on the flow velocity that is associated with the dimensions of the microchannel. We observe a linear dependence of the trapping efficiency and of the fluid flow velocity, with the channel dimensions. We determined that the highest trapping efficiency was achieved for microchannels with aspect ratio equal to one. Numerical simulation validated the impact of the device design dimensions on the trapping efficiency. This investigation indicates that the geometrical characteristics, the flow velocity, and trapping efficiency are crucial and should be considered when fabricating microfluidic devices for cell studies.
DOI
Thursday, December 7, 2017
Optical assembly of microsnap-fits fabricated by two-photon polymerization
Jannis Köhler; Yunus Kutlu; Gordon Zyla; Sarah I. Ksouri; Cemal Esen; Evgeny L. Gurevich; Andreas Ostendorf
To respond to current demands of nano- and microtechnologies, e.g., miniaturization and integration, different bottom-up strategies have been developed. These strategies are based on picking, placing, and assembly of multiple components to produce microsystems with desired features. This paper covers the fabrication of arbitrary-shaped microcomponents by two-photon polymerization and the trapping, moving, and aligning of these structures by the use of a holographic optical tweezer. The main focus is on the assembly technique based on a cantilever microsnap-fit. More precisely, mechanical properties are characterized by optical forces and a suitable geometry of the snap-fit is designed. As a result of these investigations, a fast and simple assembly technique is developed. Furthermore, disassembly is provided by an optimized design. These findings suggest that the microsnap-fit is suitable for the assembly of miniaturized systems and could broaden the application opportunities of bottom-up strategies.
DOI
To respond to current demands of nano- and microtechnologies, e.g., miniaturization and integration, different bottom-up strategies have been developed. These strategies are based on picking, placing, and assembly of multiple components to produce microsystems with desired features. This paper covers the fabrication of arbitrary-shaped microcomponents by two-photon polymerization and the trapping, moving, and aligning of these structures by the use of a holographic optical tweezer. The main focus is on the assembly technique based on a cantilever microsnap-fit. More precisely, mechanical properties are characterized by optical forces and a suitable geometry of the snap-fit is designed. As a result of these investigations, a fast and simple assembly technique is developed. Furthermore, disassembly is provided by an optimized design. These findings suggest that the microsnap-fit is suitable for the assembly of miniaturized systems and could broaden the application opportunities of bottom-up strategies.
DOI
Wednesday, November 8, 2017
Improved generation of periodic optical trap arrays using noniterative algorithm
Anita Dalal; Aniket Chowdhury; Raktim Dasgupta; Shovan Kumar Majumder
In a holographic optical tweezers setup, although the use of noniterative algorithms can result in the fast generation of multiple traps array, the performance of these algorithms is often inferior compared to iterative types of algorithms. Particularly in the case of symmetric trap arrays, the performance of noniterative algorithms is very poor. Suitability of the use of a noniterative superposition algorithm for generating symmetric trap arrays has been investigated after introducing small position disorders for the individual traps. It could be seen that the introduction of small disorders in the positions of the individual traps can significantly improve the quality of the generated trap array pattern over the case when an ideal symmetric pattern is targeted.
DOI
In a holographic optical tweezers setup, although the use of noniterative algorithms can result in the fast generation of multiple traps array, the performance of these algorithms is often inferior compared to iterative types of algorithms. Particularly in the case of symmetric trap arrays, the performance of noniterative algorithms is very poor. Suitability of the use of a noniterative superposition algorithm for generating symmetric trap arrays has been investigated after introducing small position disorders for the individual traps. It could be seen that the introduction of small disorders in the positions of the individual traps can significantly improve the quality of the generated trap array pattern over the case when an ideal symmetric pattern is targeted.
DOI
Wednesday, August 16, 2017
Scanning dimensional measurement using laser-trapped microsphere with optical standing-wave scale
Masaki Michihata; Shin-ichi Ueda; Satoru Takahashi; Kiyoshi Takamasu; Yasuhiro Takaya
We propose a laser trapping-based scanning dimensional measurement method for free-form surfaces. We previously developed a laser trapping-based microprobe for three-dimensional coordinate metrology. This probe performs two types of measurements: a tactile coordinate and a scanning measurement in the same coordinate system. The proposed scanning measurement exploits optical interference. A standing-wave field is generated between the laser-trapped microsphere and the measured surface because of the interference from the retroreflected light. The standing-wave field produces an effective length scale, and the trapped microsphere acts as a sensor to read this scale. A horizontal scan of the trapped microsphere produces a phase shift of the standing wave according to the surface topography. This shift can be measured from the change in the microsphere position. The dynamics of the trapped microsphere within the standing-wave field was estimated using a harmonic model, from which the measured surface can be reconstructed. A spherical lens was measured experimentally, yielding a radius of curvature of 2.59 mm, in agreement with the nominal specification (2.60 mm). The difference between the measured points and a spherical fitted curve was 96 nm, which demonstrates the scanning function of the laser trapping-based microprobe for free-form surfaces.
DOI
We propose a laser trapping-based scanning dimensional measurement method for free-form surfaces. We previously developed a laser trapping-based microprobe for three-dimensional coordinate metrology. This probe performs two types of measurements: a tactile coordinate and a scanning measurement in the same coordinate system. The proposed scanning measurement exploits optical interference. A standing-wave field is generated between the laser-trapped microsphere and the measured surface because of the interference from the retroreflected light. The standing-wave field produces an effective length scale, and the trapped microsphere acts as a sensor to read this scale. A horizontal scan of the trapped microsphere produces a phase shift of the standing wave according to the surface topography. This shift can be measured from the change in the microsphere position. The dynamics of the trapped microsphere within the standing-wave field was estimated using a harmonic model, from which the measured surface can be reconstructed. A spherical lens was measured experimentally, yielding a radius of curvature of 2.59 mm, in agreement with the nominal specification (2.60 mm). The difference between the measured points and a spherical fitted curve was 96 nm, which demonstrates the scanning function of the laser trapping-based microprobe for free-form surfaces.
DOI
Monday, January 23, 2017
Photothermal heating of nanoribbons
Bennett E. Smith ; Xuezhe Zhou ; E. James Davis ; Peter J. Pauzauskie
Nanoscale optical materials are of great interest for building future optoelectronic devices for information processing and sensing applications. Although heat transfer ultimately limits the maximum power at which nanoscale devices may operate, gaining a quantitative experimental measurement of photothermal heating within single nanostructures remains a challenge. Here, we measure the nonlinear optical absorption coefficient of optically trapped cadmium-sulfide nanoribbons at the level of single nanostructures through observations of their Brownian dynamics during single-beam laser trapping experiments. A general solution to the heat transfer partial differential equation is derived for nanostructures having rectilinear morphology including nanocubes and nanoribbons. Numerical electromagnetic calculations using the discrete-dipole approximation enable the simulation of the photothermal heating source function and the extraction of nonlinear optical absorption coefficients from experimental observations of single nanoribbon dynamics.
DOI
Nanoscale optical materials are of great interest for building future optoelectronic devices for information processing and sensing applications. Although heat transfer ultimately limits the maximum power at which nanoscale devices may operate, gaining a quantitative experimental measurement of photothermal heating within single nanostructures remains a challenge. Here, we measure the nonlinear optical absorption coefficient of optically trapped cadmium-sulfide nanoribbons at the level of single nanostructures through observations of their Brownian dynamics during single-beam laser trapping experiments. A general solution to the heat transfer partial differential equation is derived for nanostructures having rectilinear morphology including nanocubes and nanoribbons. Numerical electromagnetic calculations using the discrete-dipole approximation enable the simulation of the photothermal heating source function and the extraction of nonlinear optical absorption coefficients from experimental observations of single nanoribbon dynamics.
DOI
Monday, December 19, 2016
Dynamic analysis of hyperbolic waveguide resonator driven by optical gradient force
Zuo-Yang Zhong ; Hai-Lian Zhang ; Wen-Ming Zhang ; Yan Liu
As a unique type of driving force, the transverse optical gradient force has been extensively studied and applied in the nanowaveguides resonator. Recently, it is demonstrated that the optical forces in slot waveguides of hyperbolic metamaterials can be over two orders of magnitude stronger than that in conventional dielectric slot waveguides. To investigate the nonlinear dynamic characteristic of hyperbolic waveguide resonator driven by optical gradient force, a continuum elastic model of the optoresonator is presented and analytically solved using the methods of Rayleigh–Ritz and multiple scales. The results show that the optical force is strengthened with the increase of the filling ratio of silver in the hyperbolic waveguide. The resonance frequency becomes greater with the increase of the filling ratio of silver no matter what the geometric parameters and physical property parameters are. However, the steady maximum vibration amplitude becomes smaller, and the degree of system stiffness softening also reduces.
DOI
As a unique type of driving force, the transverse optical gradient force has been extensively studied and applied in the nanowaveguides resonator. Recently, it is demonstrated that the optical forces in slot waveguides of hyperbolic metamaterials can be over two orders of magnitude stronger than that in conventional dielectric slot waveguides. To investigate the nonlinear dynamic characteristic of hyperbolic waveguide resonator driven by optical gradient force, a continuum elastic model of the optoresonator is presented and analytically solved using the methods of Rayleigh–Ritz and multiple scales. The results show that the optical force is strengthened with the increase of the filling ratio of silver in the hyperbolic waveguide. The resonance frequency becomes greater with the increase of the filling ratio of silver no matter what the geometric parameters and physical property parameters are. However, the steady maximum vibration amplitude becomes smaller, and the degree of system stiffness softening also reduces.
DOI
Tuesday, February 2, 2016
Optical pulling force on a particle near the surface of a dielectric slab waveguide
Nayan Kumar Paul ; Brandon A. Kemp
Optical forces on a Rayleigh particle near the surface of a dielectric slab waveguide are considered. A light wave of the lowest-order TE0TE0 mode is used to excite the particle. The transverse and longitudinal forces acting on the particle are studied. The particle is always trapped near the surface of the slab, where the electric field intensity is high. The particle can be pushed away from or pulled toward the light source along the surface of the slab by tuning the frequency around a switching frequency. This phenomenon switches between scattering and gradient forces near the switching frequency of the dielectric slab waveguide.
DOI
Optical forces on a Rayleigh particle near the surface of a dielectric slab waveguide are considered. A light wave of the lowest-order TE0TE0 mode is used to excite the particle. The transverse and longitudinal forces acting on the particle are studied. The particle is always trapped near the surface of the slab, where the electric field intensity is high. The particle can be pushed away from or pulled toward the light source along the surface of the slab by tuning the frequency around a switching frequency. This phenomenon switches between scattering and gradient forces near the switching frequency of the dielectric slab waveguide.
DOI
Tuesday, August 18, 2015
Generalized phase contrast-enhanced diffractive coupling to light-driven microtools
Mark Villangca ; Andrew Bañas ; Darwin Palima ; Jesper Glückstad
We have previously demonstrated on-demand dynamic coupling to optically manipulated microtools coined as wave-guided optical waveguides using diffractive techniques on a “point and shoot” approach. These microtools are extended microstructures fabricated using two-photon photopolymerization and function as free-floating optically trapped waveguides. Dynamic coupling of focused light via these structures being moved in three-dimensional space is done holographically. However, calculating the necessary holograms is not straightforward when using counter-propagating trapping geometry. The generation of the coupling spots is done in real time following the position of each microtool with the aid of an object tracking routine. This approach allows continuous coupling of light through the microtools which can be useful in a variety of biophotonics applications. To complement the targeted-light delivery capability of the microtools, the applied spatial light modulator has been illuminated with a properly matched input beam cross section based on the generalized phase contrast method. Our results show a significant gain in the output at the tip of each microtool as measured from the fluorescence signal of the trapping medium. The ability to switch from on-demand to continuous addressing with efficient illumination leverages our microtools for potential applications in stimulation and near-field-based biophotonics on cellular scales.
DOI
We have previously demonstrated on-demand dynamic coupling to optically manipulated microtools coined as wave-guided optical waveguides using diffractive techniques on a “point and shoot” approach. These microtools are extended microstructures fabricated using two-photon photopolymerization and function as free-floating optically trapped waveguides. Dynamic coupling of focused light via these structures being moved in three-dimensional space is done holographically. However, calculating the necessary holograms is not straightforward when using counter-propagating trapping geometry. The generation of the coupling spots is done in real time following the position of each microtool with the aid of an object tracking routine. This approach allows continuous coupling of light through the microtools which can be useful in a variety of biophotonics applications. To complement the targeted-light delivery capability of the microtools, the applied spatial light modulator has been illuminated with a properly matched input beam cross section based on the generalized phase contrast method. Our results show a significant gain in the output at the tip of each microtool as measured from the fluorescence signal of the trapping medium. The ability to switch from on-demand to continuous addressing with efficient illumination leverages our microtools for potential applications in stimulation and near-field-based biophotonics on cellular scales.
DOI
Friday, September 19, 2014
Single-beam three-dimensional optical trapping at extremely low insertion angles via optical fiber optimization
Steven Ross; Mark F. Murphy; Francis Lilley; Michael J. Lalor; David R. Burton
Employing optical fiber to deliver the trapping laser to the sample chamber significantly reduces the size and costs of optical tweezers (OT). The utilization of fiber decouples the OT from the microscope, providing scope for system portability, and the potential for uncomplicated integration with other advanced microscopy systems. For use with an atomic force microscope, the fiber must be inserted at an angle of 10 deg to the plane of the sample chamber floor. However, the literature states that optical trapping with a single fiber inserted at an angle ≤20 deg is not possible. This paper investigates this limitation and proposes a hypothesis that explains it. Based on this explanation, a tapered-fiber optical tweezer system is developed. This system demonstrates that such traps can indeed be made to function in three-dimensions (3-D) at insertion angles of ≤10 deg using relatively low optical powers, provided the fiber taper is optimized. Three such optimized tapered fiber tips are presented, and their ability to optically trap both organic and inanimate material in 3-D is demonstrated. The near-horizontal insertion angle introduced a maximum trapping range (MTR). The MTR of the three tips is determined empirically, evaluated against simulated data, and found to be tunable through taper optimization.
DOI
Employing optical fiber to deliver the trapping laser to the sample chamber significantly reduces the size and costs of optical tweezers (OT). The utilization of fiber decouples the OT from the microscope, providing scope for system portability, and the potential for uncomplicated integration with other advanced microscopy systems. For use with an atomic force microscope, the fiber must be inserted at an angle of 10 deg to the plane of the sample chamber floor. However, the literature states that optical trapping with a single fiber inserted at an angle ≤20 deg is not possible. This paper investigates this limitation and proposes a hypothesis that explains it. Based on this explanation, a tapered-fiber optical tweezer system is developed. This system demonstrates that such traps can indeed be made to function in three-dimensions (3-D) at insertion angles of ≤10 deg using relatively low optical powers, provided the fiber taper is optimized. Three such optimized tapered fiber tips are presented, and their ability to optically trap both organic and inanimate material in 3-D is demonstrated. The near-horizontal insertion angle introduced a maximum trapping range (MTR). The MTR of the three tips is determined empirically, evaluated against simulated data, and found to be tunable through taper optimization.
DOI
Friday, August 1, 2014
Near real-time measurement of forces applied by an optical trap to a rigid cylindrical object
Joseph Glaser; David Hoeprich; Andrew Resnick
An automated data acquisition and processing system is established to measure the force applied by an optical trap to an object of unknown composition in real time. Optical traps have been in use for the past 40 years to manipulate microscopic particles, but the magnitude of applied force is often unknown and requires extensive instrument characterization. Measuring or calculating the force applied by an optical trap to nonspherical particles presents additional difficulties which are also overcome with our system. Extensive experiments and measurements using well-characterized objects were performed to verify the system performance.
DOI
DOI
Friday, July 4, 2014
To construct a stable and tunable optical trap in the focal region of a high numerical aperture lens
Gokulakrishnan Kandasamy; Suresh Ponnan; T. V. Sivasubramonia Pillai; Rajesh K. Balasundaram
Based on the diffraction theory, the focusing properties of a radially polarized quadratic Bessel–Gaussian beam (QBG) with on-axis radial phase variance wavefront are investigated theoretically in the focal region of a high numerical aperture (NA) objective lens. The phase wavefront C and pupil beam parameter μ of QBG are the functions of the radial coordinate. The detailed numerical calculation of the focusing property of a QBG beam is presented. The numerical calculation shows that the beam parameter μ and phase parameter C have greater effect on the total electric field intensity distribution. It is observed that under the condition of different μ, evolution principle of focal pattern differs very remarkably on increasing C. Also, some different focal shapes may appear, including rhombic shape, quadrangular shape, two-spherical crust focus shape, two-peak shape, one dark hollow focus, two dark hollow focuses pattern, and triangle dark hollow focus, which find wide optical applications such as optical trapping and nanopatterning.
DOI
Based on the diffraction theory, the focusing properties of a radially polarized quadratic Bessel–Gaussian beam (QBG) with on-axis radial phase variance wavefront are investigated theoretically in the focal region of a high numerical aperture (NA) objective lens. The phase wavefront C and pupil beam parameter μ of QBG are the functions of the radial coordinate. The detailed numerical calculation of the focusing property of a QBG beam is presented. The numerical calculation shows that the beam parameter μ and phase parameter C have greater effect on the total electric field intensity distribution. It is observed that under the condition of different μ, evolution principle of focal pattern differs very remarkably on increasing C. Also, some different focal shapes may appear, including rhombic shape, quadrangular shape, two-spherical crust focus shape, two-peak shape, one dark hollow focus, two dark hollow focuses pattern, and triangle dark hollow focus, which find wide optical applications such as optical trapping and nanopatterning.
DOI
Tuesday, April 30, 2013
Design of hybrid optical tweezers system for controlled three-dimensional micromanipulation
Yoshio Tanaka; Shogo Tsutsui; Hiroyuki Kitajima
Three-dimensional (3D) micro/nano-manipulation using optical tweezers is a significant technique for various scientific fields ranging from biology to nanotechnology. For the dynamic handling of multiple/individual micro-objects in a true 3D working space, we present an improved hybrid optical tweezers system consisting of two multibeam techniques. These two techniques include the generalized phase contrast method with a spatial light modulator and the time-shared scanning method with a two-axis steering mirror and an electrically focus-tunable lens. Unlike our previously reported system that could only handle micro-objects in a two and half dimensional working space, the present system has high versatility for controlled manipulation of multiple micro-objects in a true 3D working space. The controlled rotation of five beads forming a pentagon, that of four beads forming a tetrahedron about arbitrary axes, and the fully automated assembly and subsequent 3D translation of micro-bead arrays are successfully demonstrated as part of the 3D manipulation experiment.
DOI
Three-dimensional (3D) micro/nano-manipulation using optical tweezers is a significant technique for various scientific fields ranging from biology to nanotechnology. For the dynamic handling of multiple/individual micro-objects in a true 3D working space, we present an improved hybrid optical tweezers system consisting of two multibeam techniques. These two techniques include the generalized phase contrast method with a spatial light modulator and the time-shared scanning method with a two-axis steering mirror and an electrically focus-tunable lens. Unlike our previously reported system that could only handle micro-objects in a two and half dimensional working space, the present system has high versatility for controlled manipulation of multiple micro-objects in a true 3D working space. The controlled rotation of five beads forming a pentagon, that of four beads forming a tetrahedron about arbitrary axes, and the fully automated assembly and subsequent 3D translation of micro-bead arrays are successfully demonstrated as part of the 3D manipulation experiment.
DOI
Tuesday, February 14, 2012
Improved direct binary search-based algorithm for generating holograms for the application of holographic optical tweezers
XuDong Zhao, Jing Li, Tao Tao, Qian Long, and Xiaoping Wu
This paper presents an improved direct binary search (DBS)-based algorithm for generating holograms to holographic optical tweezers. The simulations show that the improved algorithm greatly enhances computation speed while maintaining high hologram efficiency and high-intensity homogeneous target spots. The improved algorithm was applied to generate holographic optical tweezers in several experiments. The experiments demonstrate that real-time trap and manipulation can be realized with the improved algorithm if the number of trapped microparticles is small.
DOI
This paper presents an improved direct binary search (DBS)-based algorithm for generating holograms to holographic optical tweezers. The simulations show that the improved algorithm greatly enhances computation speed while maintaining high hologram efficiency and high-intensity homogeneous target spots. The improved algorithm was applied to generate holographic optical tweezers in several experiments. The experiments demonstrate that real-time trap and manipulation can be realized with the improved algorithm if the number of trapped microparticles is small.
DOI
Monday, August 16, 2010
Holographic optical manipulation of motor-driven membranous structures in living NG-108 cells
Arnau Farré, Carol López-Quesada, Jordi Andilla, Estela Martín-Badosa, and Mario Montes-Usategui
Optical tweezer experiments have partially unveiled the mechanical properties of processive motor proteins while driving polystyrene or silica microbeads in vitro. However, the set of forces underlying the more complex transport mechanisms in living samples remains poorly understood. Several studies have shown that optical tweezers are capable of trapping vesicles and organelles in the cytoplasm of living cells, which can be used as handles to mechanically interact with engaged (active) motors, or other components regulating transport. This may ultimately enable the exploration of the mechanics of this trafficking mechanism in vivo. These cell manipulation experiments have been carried out using different strategies to achieve dynamic beam steering capable of trapping thesesubcellular structures. We report here the first trapping and manipulation, to our knowledge, of such small motor-propelled cargos in living cells using holographic technology.
DOI
Optical tweezer experiments have partially unveiled the mechanical properties of processive motor proteins while driving polystyrene or silica microbeads in vitro. However, the set of forces underlying the more complex transport mechanisms in living samples remains poorly understood. Several studies have shown that optical tweezers are capable of trapping vesicles and organelles in the cytoplasm of living cells, which can be used as handles to mechanically interact with engaged (active) motors, or other components regulating transport. This may ultimately enable the exploration of the mechanics of this trafficking mechanism in vivo. These cell manipulation experiments have been carried out using different strategies to achieve dynamic beam steering capable of trapping thesesubcellular structures. We report here the first trapping and manipulation, to our knowledge, of such small motor-propelled cargos in living cells using holographic technology.
DOI
Monday, November 30, 2009
Design and realization of a high-stability optical tweezer
Slawomir Drobczynski, Pascal Hébraud, Jean Pierre Munch, and Sébastien Harlepp
We present a method in which we stabilize mechanically an optical tweezer setup over a period ranging up to 30 min. A feedback loop is used to correct the mechanical and thermal drifts. The position of a fixed object on the sample surface is measured with a CCD device and its fluctuations analyzed and used to maintain its position fixed with threepiezoelectric devices. With this setup, we obtain a spatial stability of 1.5 nm in the radial direction and 5 nm in the axial direction. This method opens the route for real-time measurements of kinetics of macromolecules association, at a single molecule level, on very long time scales.
We present a method in which we stabilize mechanically an optical tweezer setup over a period ranging up to 30 min. A feedback loop is used to correct the mechanical and thermal drifts. The position of a fixed object on the sample surface is measured with a CCD device and its fluctuations analyzed and used to maintain its position fixed with threepiezoelectric devices. With this setup, we obtain a spatial stability of 1.5 nm in the radial direction and 5 nm in the axial direction. This method opens the route for real-time measurements of kinetics of macromolecules association, at a single molecule level, on very long time scales.
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