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Journal ArticleDOI

Scanning-force microscope based on an optical trap

01 Oct 1993-Optics Letters (Optical Society of America)-Vol. 18, Iss: 19, pp 1678-1680
TL;DR: This gentler technique should improve the sensitivity of scanning-force microscopy for the imaging of soft samples in aqueous media.
Abstract: An optically trapped prolate glass stylus is the force-sensing element of a novel scanning-force microscope. Stylus displacement is detected with the use of the forward scatter of the trapping laser beam. Radiation forces owing to the three-dimensional intensity distribution near the focus permit the stylus to be both positioned with fine control and oriented along the z (optic) axis. Details of 20-nm size appear in traces recorded with a crude stylus in a trap formed with 1064-nm radiation. The spring constant of the optical-force transducer is below 10−4 N/m, which is to be compared with ∼0.1 N/m for typical mechanical cantilevers used in atomic-force microscopy. This gentler technique should improve the sensitivity of scanning-force microscopy for the imaging of soft samples in aqueous media.
Citations
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Journal ArticleDOI
TL;DR: The usefulness of the proposed method for three-dimensional microfabrication with photopolymerization stimulated by two-photon absorption with a pulsed infrared laser has been verified by fabrication of several kinds of microstructure by use of a resin consisting of photoinitiators, urethane acrylate monomers, and urethanacrylate oligomers.
Abstract: We propose a method for three-dimensional microfabrication with photopolymerization stimulated by two-photon absorption with a pulsed infrared laser An experimental system for the microfabrication has been developed with a Ti:sapphire laser whose oscillating wavelength and pulse width are 790 nm and 200 fs, respectively The usefulness of the proposed method has been verified by fabrication of several kinds of microstructure by use of a resin consisting of photoinitiators, urethane acrylate monomers, and urethane acrylate oligomers

1,660 citations

Journal ArticleDOI
Arthur Ashkin1
TL;DR: Early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology are reviewed.
Abstract: The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary role in areas of the physical and biological sciences. This paper reviews the early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology. Some further major achievements of these rapidly developing methods also are considered.

1,346 citations

Journal ArticleDOI
TL;DR: The state-of-the-art in optical trapping at the nanoscale is reviewed, with an emphasis on some of the most promising advances, such as controlled manipulation and assembly of individual and multiple nanostructures, force measurement with femtonewton resolution, and biosensors.
Abstract: Optical trapping and manipulation of micrometre-sized particles was first reported in 1970. Since then, it has been successfully implemented in two size ranges: the subnanometre scale, where light-matter mechanical coupling enables cooling of atoms, ions and molecules, and the micrometre scale, where the momentum transfer resulting from light scattering allows manipulation of microscopic objects such as cells. But it has been difficult to apply these techniques to the intermediate - nanoscale - range that includes structures such as quantum dots, nanowires, nanotubes, graphene and two-dimensional crystals, all of crucial importance for nanomaterials-based applications. Recently, however, several new approaches have been developed and demonstrated for trapping plasmonic nanoparticles, semiconductor nanowires and carbon nanostructures. Here we review the state-of-the-art in optical trapping at the nanoscale, with an emphasis on some of the most promising advances, such as controlled manipulation and assembly of individual and multiple nanostructures, force measurement with femtonewton resolution, and biosensors.

855 citations

Journal ArticleDOI
TL;DR: Comparison of trapping forces for latex and gold spheres demonstrates that the gradient force is the major determinant of trapping strength and that competing effects, such as scattering or radiometric forces, are relatively minor.
Abstract: Metallic objects reflect light and have generally been considered poor candidates for optical traps, particularly with optical tweezers, which rely on a gradient force to provide trapping. We demonstrate that stable trapping can occur with optical tweezers when they are used with small metallic Rayleigh particles. In this size regime, the scattering pictures for metals and dielectrics are similar, and the larger polarizability of metals implies that trapping forces are greater. The latter fact makes the use of metal particles attractive for certain biological applications. Comparison of trapping forces for latex and gold spheres demonstrates that the gradient force is the major determinant of trapping strength and that competing effects, such as scattering or radiometric forces, are relatively minor.

738 citations

Journal ArticleDOI
TL;DR: A model is provided for the essential mechanism of intensity shifts as first-order far-field interference between the outgoing laser beam and scattered light from the trapped particle, where the latter is phase advanced owing to the Gouy phase anomaly.
Abstract: The lateral position of an optically trapped object in a microscope can be monitored with a quadrant photodiode to within nanometers or better by measurement of intensity shifts in the back focal plane of the lens that is collimating the outgoing laser light. This detection is largely independent of the position of the trap in the field of view. We provide a model for the essential mechanism of this type of detection, giving a simple, closed-form analytic solution with simplifying assumptions. We identify intensity shifts as first-order far-field interference between the outgoing laser beam and scattered light from the trapped particle, where the latter is phase advanced owing to the Gouy phase anomaly. This interference also reflects momentum transfer to the particle, giving the spring constant of the trap. Our response formula is compared with the results of experiments.

659 citations

References
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Journal ArticleDOI
TL;DR: The atomic force microscope as mentioned in this paper is a combination of the principles of the scanning tunneling microscope and the stylus profilometer, which was proposed as a method to measure forces as small as 10-18 N. As one application for this concept, they introduce a new type of microscope capable of investigating surfaces of insulators on an atomic scale.
Abstract: The scanning tunneling microscope is proposed as a method to measure forces as small as 10-18 N. As one application for this concept, we introduce a new type of microscope capable of investigating surfaces of insulators on an atomic scale. The atomic force microscope is a combination of the principles of the scanning tunneling microscope and the stylus profilometer. It incorporates a probe that does not damage the surface. Our preliminary results in air demonstrate a lateral resolution of 30 A and a vertical resolution less than 1 A.

12,344 citations

Journal ArticleDOI
TL;DR: Optical trapping of dielectric particles by a single-beam gradient force trap was demonstrated for the first reported time, confirming the concept of negative light pressure due to the gradient force.
Abstract: Optical trapping of dielectric particles by a single-beam gradient force trap was demonstrated for the first reported time. This confirms the concept of negative light pressure due to the gradient force. Trapping was observed over the entire range of particle size from 10 μm to ~25 nm in water. Use of the new trap extends the size range of macroscopic particles accessible to optical trapping and manipulation well into the Rayleigh size regime. Application of this trapping principle to atom trapping is considered.

6,434 citations

Journal ArticleDOI
TL;DR: Understanding the optical behavior of the microscope system has indicated how to optimize specimen preparation, data collection, and processing protocols to obtain significantly improved images.

264 citations

Journal ArticleDOI
TL;DR: In this paper, a laser trapping-ablation system comprised of CW and pulsed Nd3+:YAG lasers as well as an optical microscope was developed for three-dimensional manipulation of various kinds of particles and laser ablation of a single optically trapped, poly(methyl methacrylate) latex particle in water.
Abstract: We developed a laser trapping‐ablation system comprised of CW and pulsed Nd3+:YAG lasers as well as of an optical microscope. Three‐dimensional manipulation of various kinds of particles and laser ablation of a single optically trapped, poly(methyl methacrylate) latex particle in water were demonstrated. A minute hole with its diameter of ∼sub‐μm was fabricated on the latex particle (∼6 μm diameter). The hole size produced was much smaller than the effective diameter of the excitation laser beam, suggesting nonlinear optical (self‐focusing of the laser beam) and photochemical (multiphoton absorption) mechanisms for the present laser trapping ablation. Characteristic features of the laser trapping‐ablation are discussed in detail.

190 citations

Journal ArticleDOI
TL;DR: An optical laser differential interferometer, based on a modified differential interference contrast microscope, has been developed to measure the thermal motion of microscopic protrusions (stereocilia) that are the sites of mechanoelectrical transduction in auditory hair cells, and experimental data were found to be in agreement with theoretical estimates.
Abstract: An optical laser differential interferometer, based on a modified differential interference contrast microscope, has been developed to measure the thermal motion of microscopic protrusions (stereocilia) that are the sites of mechanoelectrical transduction in auditory hair cells. The measurement sensitivity was limited at high frequencies mainly by shot noise, at intermediate frequencies by acoustic interference, and at low frequencies by thermal drift. The power spectral density of the instrumental noise was found to be as low as 1 pm/Hz in the shot noise regime. We could, thus, measure the Brownian motion of hair bundles over the frequency range from 1 Hz–100 kHz. Experimental data that test and demonstrate the sensitivity and spatial discrimination of the instrument were found to be in agreement with theoretical estimates.

177 citations