Investigation of the center intensity of first- and second-order Laguerre-Gaussian beams with linear and circular polarization

Iketaki, Yoshinori; Watanabe, Takeshi; Bokor, Nándor; Fujii, Masaaki

doi:10.1364/ol.32.002357

Cited by 52 publications

(46 citation statements)

References 10 publications

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“…4. This is consistent with the behavior of the LG beams focused tightly by a high numerical aperture objective lens [12][13][14]. In other words, the change in R s due to the circular polarization direction of the LG beams is additional evidence for proper trapping on the bright rings of the focused LG beams.…”

supporting

confidence: 83%

“…Hence, the polarization of the trapping light is expected to be independent of the objects' revolution; i.e., J rÀpol =J lÀpol should become unity.This deviation in the experimental results from the above perspective also relates to the polarization-dependent deformation of a tightly focused LGbeam pattern [12][13][14]. Here, non-paraxial solutions of the Helmholtz equation [13][14][15] are suitable for discussing the angular-momentum properties of tightly focused circular- symmetric LG beams.…”

mentioning

confidence: 98%

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Precise revolution control in three-dimensional off-axis trapping with single Laguerre-Gaussian beam

Otsu¹,

Ando²,

Takiguchi³

et al. 2015

Opt Rev

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We report the precise study of orbital angular momentum transfer from Laguerre-Gaussian (LG) beams to submicrometer-sized dielectric spheres. Stable three-dimensional off-axis trapping of the spheres was achieved and confirmed by the constant behavior of the sphere's revolution radius against the trapping LG-beam power. By measuring the revolutions of the sphere that was trapped and revolved in mid-water, we confirmed excellent linearity between the revolution rate and the trapping light free from the hydrodynamic coupling with walls of a sample chamber. This result suggests a torque source of precise controllability, which will contribute to the study of biological molecules, nonequilibrium statistical physics, and micromachines.Keywords Holographic optical tweezers Á Optical vortices Á Phase only spatial light modulator Optical vortices (OVs) are known as a series of light beams with singular wavefronts. Due to their phase property, OVs carry orbital angular momenta around their beam axes to have an ability of revolving objects under light irradiation [1,2]. This suggests the possibility of maintaining the objects' revolutions by continuous irradiation of OVs without any dynamical control. Such revolutions have been achieved two-dimensionally on cover glasses [3][4][5] except for a few studies reporting three-dimensional revolution in mid-water with the help of gravity [6] or an additional Gaussian beam [7] for fixing the axial trapping positions. Whether a single OV can achieve three-dimensional trapping in cooperation with object's revolution remains unclear, but the authors [8] recently established direct evidence of three-dimensional trapping by LaguerreGaussian (LG) beams that are the most common embodiments of OVs.In this report, we study the controllability of the revolution of micrometer-sized polystyrene spheres trapped by LG beams in mid-water. The trapping LG beams were generated by a holographic phase-amplitude modulation scheme to obtain high-quality ones [9]. To suppress the interaction of the trapped spheres with walls caused by Brownian motion in the axial direction, we observed the revolution of polystyrene spheres trapped in mid-water more than 1.5 lm away from the surface of a cover glass. Measurements of revolution speed with varying LG-beam power revealed precise controllability of the revolutions by the trapping light power, suggesting a novel optical tool that is especially useful for investigating the torsional properties of biological molecules [10] and driving rotational micromachines [11]. Figure 1 schematically shows the present experimental setup. The linearly-polarized laser output (wavelength k ¼ 1; 064 nm) was expanded by a beam expander and shaped into a top-hat intensity profile through an aperture. The trapping LG beams were obtained by converting the top-hat light with holographic phase patterns displayed on a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM). The holographic patterns were prepared by a simultaneous phase-amplitude modulation method to gen...

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supporting

confidence: 83%

mentioning

confidence: 98%

Precise revolution control in three-dimensional off-axis trapping with single Laguerre-Gaussian beam

Otsu¹,

Ando²,

Takiguchi³

et al. 2015

Opt Rev

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“…Regarding the magnitude of the fields near r = 0 Zurita-Sánchez et al [30] have shown that, for the strongly focused azimuthally- polarized beam they studied, the magnetic interaction overcomes the electric interaction near the phase singularity; recently, their findings have been corroborated by the theoretical study of Klimov et al [49] in the case of focused Laguerre-Gaussian beams. Finally, in their research on highly-focused TL beams, Monteiro et al [63], Iketaki et al [59] and Klimov et al [49] report that interesting effects only occur when ℓ = 1, 2 and σ = −1. The overall similarities are no coincidence, for the vector potential Eq.…”

Section: Figmentioning

confidence: 97%

Formulation of the twisted-light–matter interaction at the phase singularity: The twisted-light gauge

2015

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Twisted light is light carrying orbital angular momentum. The profile of such a beam is a ring-like structure with a node at the beam axis, where a phase singularity exists. Due to the strong spatial inhomogeneity the mathematical description of twisted-light-matter interaction is non-trivial, in particular close to the phase singularity, where the commonly used dipole-moment approximation cannot be applied. In this paper we show that, if the handedness of circular polarization and the orbital angular momentum of the twisted-light beam have the same sign, a Hamiltonian similar to the dipole-moment approximation can be derived. However, if the signs differ, in general the magnetic parts of the light beam become of significant importance and an interaction Hamiltonian which only accounts for electric fields is inappropriate. We discuss the consequences of these findings for twisted-light excitation of a semiconductor nanostructures, e.g., a quantum dot, placed at the phase singularity.

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“…Standard fiber optic technologies can then be used for positioning the NSOM fiber and measuring the signal coupled into the fiber tip. Once the tip is protected by the fiber optic ferrule, this method offers better repeatability and is less time consuming to implement than the normal method which uses the light scattered off a nano-particle or a fluorescent bead for imaging the focal spot [14,16]. Figure 5(a) shows a 2 μm × 2 μm image of the focal spot by x-y scan of the NSOM fiber tip.…”

Section: Methodsmentioning

confidence: 99%

“…The vortex phase plate (VPP) plus the subsequent quarter-wave plate shaped the beam that upon focusing by the apochromatic microscope objective with high numerical aperture (0.9), the beam cross-section exhibits a doughnut shape central dark region appropriate for achieving lateral superresolution. The central dark region is due to the cancellation of the z-component of the electric field at the focal plane as described in [14] using the formula in [15]. Since the spatial resolution increases with depletion power [16], ideally, one would like to make use of the maximum depletion power available.…”

Section: Optical Setupmentioning

confidence: 99%

A Low Cost and Versatile STED Superresolution Fluorescent Microscope

McBride¹,

Su²,

Kameoka³

et al. 2013

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A versatile and inexpensive super-resolution fluorescent microscope that functions as easily as a conventional confocal microscope is described. Components of the microscope were designed on a platform which was placed atop a surplus microscope frame. All optical components and equipments used are given. The excitation and depletion beams are extracted from a compact low-cost supercontinuum light source. The focal spot of the depletion beam at the focal plane is studied and imaged by a 100 nm aperture near-field fiber tip. The collinear excitation and depletion beam focused by a 0.9 numerical aperture microscope objective produce a 90 nm lateral super-resolution as verified by imaging 100 nm diameter fluorescent beads.

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Investigation of the center intensity of first- and second-order Laguerre-Gaussian beams with linear and circular polarization

Cited by 52 publications

References 10 publications

Precise revolution control in three-dimensional off-axis trapping with single Laguerre-Gaussian beam

Precise revolution control in three-dimensional off-axis trapping with single Laguerre-Gaussian beam

Formulation of the twisted-light–matter interaction at the phase singularity: The twisted-light gauge

A Low Cost and Versatile STED Superresolution Fluorescent Microscope

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