scholarly journals Theory of optical tweezing of dielectric microspheres in chiral host media and its applications

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rfaqat Ali ◽  
Rafael S. Dutra ◽  
Felipe A. Pinheiro ◽  
Felipe S. S. Rosa ◽  
Paulo A. Maia Neto
Keyword(s):  
Optical Tweezers ◽  
High Refractive Index ◽  
Mechanical Effect ◽  
Optical Force ◽  
Host Medium ◽  
Dielectric Particles ◽  
Chirality Parameter ◽  
First Time ◽  
Optical Torque ◽  
Angle Of Rotation

Abstract We report for the first time the theory of optical tweezers of spherical dielectric particles embedded in a chiral medium. We develop a partial-wave (Mie) expansion to calculate the optical force acting on a dielectric microsphere illuminated by a circularly-polarized, highly focused laser beam. When choosing a polarization with the same handedness of the medium, the axial trap stability is improved, thus allowing for tweezing of high-refractive-index particles. When the particle is displaced off-axis by an external force, its equilibrium position is rotated around the optical axis by the mechanical effect of an optical torque. Both the optical torque and the angle of rotation are greatly enhanced in the presence of a chiral host medium when considering radii a few times larger than the wavelength. In this range, the angle of rotation depends strongly on the microsphere radius and the chirality parameter of the host medium, opening the way for a quantitative characterization of both parameters. Measurable angles are predicted even in the case of naturally occurring chiral solutes, allowing for a novel all-optical method to locally probe the chiral response at the nanoscale.

scholarly journals Optomechanical measurement of photon spin angular momentum and optical torque in integrated photonic devices

2016 ◽  
Vol 2 (9) ◽  
pp. e1600485 ◽  
Author(s):  
Li He ◽  
Huan Li ◽  
Mo Li
Keyword(s):  
Angular Momentum ◽  
Optical Tweezers ◽  
Laser Cooling ◽  
Photonic Devices ◽  
Mechanical Effect ◽  
Linear Momentum ◽  
Polarization Degree ◽  
Optical Forces ◽  
Spin Angular Momentum ◽  
Optical Torque

Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon’s polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry.

ROTATIONAL PROPERTIES OF MICRO-SLABS DRIVEN BY LINEARLY-POLARIZED LIGHT

2005 ◽  
Vol 14 (03) ◽  
pp. 375-382 ◽  
Author(s):  
CHIH-LANG LIN ◽  
IRÈNE WANG ◽  
MARC PIERRE ◽  
ISABELLE COLOMBIER ◽  
CHANTAL ANDRAUD ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Polarized Light ◽  
Polarization Plane ◽  
Light Polarization ◽  
Good Prediction ◽  
Polarization Anisotropy ◽  
Two Photon ◽  
Flat Slabs ◽  
Linearly Polarized ◽  
Optical Torque

We study the rotational motion of objects trapped in a focused laser beam (optical tweezers). Micrometer-sized flat slabs are fabricated using two-photon photopolymerization. These objects, trapped by linearly-polarized light, tend to align parallel to the polarization plane. This alignment effect is attributed to the polarization anisotropy resulting from the object shape and we present a simple electromagnetic approach to estimate the resulting optical torque. Micro-rotors of different sizes are studied experimentally. We characterize the behavior of micro-objects when the light polarization is rotated at constant speed. Our theoretical approach gives a good prediction of how the size of micro-objects affects their rotation efficiency.

scholarly journals Suppression of scattering for small dielectric particles: anapole mode and invisibility

2017 ◽  
Vol 375 (2090) ◽  
pp. 20160069 ◽  
Author(s):  
Boris Luk'yanchuk ◽  
Ramón Paniagua-Domínguez ◽  
Arseniy I. Kuznetsov ◽  
Andrey E. Miroshnichenko ◽  
Yuri S. Kivshar
Keyword(s):  
Refractive Index ◽  
Electric Dipole ◽  
Fano Resonance ◽  
Optical Materials ◽  
High Refractive Index ◽  
Destructive Interference ◽  
Total Scattering ◽  
Dipole Radiation ◽  
New Horizons ◽  
Dielectric Particles

We reveal that an isotropic, homogeneous, subwavelength particle with high refractive index can produce ultra-small total scattering. This effect, which follows from the inhibition of the electric dipole radiation, can be identified as a Fano resonance in the scattering efficiency and is associated with the excitation of an anapole mode in the particle. This anapole mode is non-radiative and emerges from the destructive interference of electric and toroidal dipoles. The invisibility effect could be useful for the design of highly transparent optical materials. This article is part of the themed issue ‘New horizons for nanophotonics’.

COUNTING UNFOLDING EVENTS IN STRETCHED HELICES WITH INDUCED OSCILLATION BY OPTICAL TWEEZERS

2012 ◽  
Vol 17 ◽  
pp. 44-53
Author(s):  
ROMMEL GAUD BACABAC ◽  
ROLAND OTADOY
Keyword(s):  
Optical Tweezers ◽  
Viscoelastic Properties ◽  
Globular Proteins ◽  
Optical Traps ◽  
Living Matter ◽  
Damped Harmonic Oscillator ◽  
Catch Up ◽  
Correlation Measures ◽  
Complex Phenomena ◽  
First Time

Correlation measures based on embedded probe fluctuations, single or paired, are now widely used for characterizing the viscoelastic properties of biological samples. However, more robust applications using this technique are still lacking. Considering that the study of living matter routinely demonstrates new and complex phenomena, mathematical and experimental tools for analysis have to catch up in order to arrive at newer insights. Therefore, we derive ways of probing non-equilibrium events in helical biopolymers provided by stretching beyond thermal forces. We generalize, for the first time, calculations for winding turn probabilities to account for unfolding events in single fibrous biopolymers and globular proteins under tensile stretching using twin optical traps. The approach is based on approximating the ensuing probe fluctuations as originating from a damped harmonic oscillator under oscillatory forcing.

scholarly journals Sodium Alginate Cross-Linkable Planar 1D Photonic Crystals as a Promising Tool for Pb2+ Detection in Water

Chemosensors ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 37 ◽  
Author(s):  
Andrea Dodero ◽  
Paola Lova ◽  
Silvia Vicini ◽  
Maila Castellano ◽  
Davide Comoretto
Keyword(s):  
Refractive Index ◽  
Photonic Crystals ◽  
Sodium Alginate ◽  
Spectral Response ◽  
High Refractive Index ◽  
Polluted Water ◽  
Ionic Exchange ◽  
Promising Tool ◽  
Rural Environments ◽  
First Time

Due to its high toxicity, Pb2+ pollution is a serious threat for human health and environments. However, in situ real-time detection of Pb2+ pollution is difficult and laboratory instruments are usually required. Then, the possibility to monitor water quality without laboratory instruments could lead to the extensive assessment of polluted water sources, especially in rural environments and developing countries where large lead concentrations are often found in surface water. Consequently, new simple colorimetric sensors are highly interesting in the field. In this work we report for the first time disposable polymer planar 1D photonic crystals made of poly (N-vinylcarbazole) as high refractive index medium and sodium alginate as low refractive index and active medium for the detection of Pb2+ in water. The detection relies on the ionic exchange occurring into the alginate matrix. This process effectively induces a physical cross-linking phenomenon, which inhibits water solubilization of the polymer. In turn, this affects the spectral response of the planar 1D photonic crystals modifying its color.

Nanonewton optical force trap employing anti-reflection coated, high-refractive-index titania microspheres

2012 ◽  
Vol 6 (7) ◽  
pp. 469-473 ◽  
Author(s):  
Anita Jannasch ◽  
Ahmet F. Demirörs ◽  
Peter D. J. van Oostrum ◽  
Alfons van Blaaderen ◽  
Erik Schäffer
Keyword(s):  
Refractive Index ◽  
High Refractive Index ◽  
Optical Force ◽  
Titania Microspheres

scholarly journals Micromanipulation of amyloplasts with optical tweezers in Arabidopsis stems

2020 ◽  
Author(s):  
Yoshinori Abe ◽  
Keisuke Meguriya ◽  
Takahisa Matsuzaki ◽  
Teruki Sugiyama ◽  
Hiroshi Y. Yoshikawa ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Near Infrared ◽  
Initial Step ◽  
Optical Force ◽  
Physical Interaction ◽  
Laser Focus ◽  
Close Proximity ◽  
Endodermal Cells ◽  
Vacuolar Membranes

AbstractIntracellular sedimentation of highly dense, starch-filled amyloplasts toward the gravity vector is likely a key initial step for gravity sensing in plants. However, recent live-cell imaging technology revealed that most amyloplasts continuously exhibit dynamic, saltatory movements in the endodermal cells of Arabidopsis stems. These complicated movements led to questions about what type of amyloplast movement triggers gravity sensing. Here we show that a confocal microscope equipped with optical tweezers can be a powerful tool to trap and manipulate amyloplasts noninvasively, while simultaneously observing cellular responses such as vacuolar dynamics in living cells. A near-infrared (λ = 1064 nm) laser that was focused into the endodermal cells at 1 mW of laser power attracted and captured amyloplasts at the laser focus. The optical force exerted on the amyloplasts was theoretically estimated to be up to 1 pN. Interestingly, endosomes and trans-Golgi networks were trapped at 30 mW but not at 1 mW, which is probably due to lower refractive indices of these organelles than that of the amyloplasts. Because amyloplasts are in close proximity to vacuolar membranes in endodermal cells, their physical interaction could be visualized in real time. The vacuolar membranes drastically stretched and deformed in response to the manipulated movements of amyloplasts by optical tweezers. Our new method provides deep insights into the biophysical properties of plant organelles in vivo and opens a new avenue for studying gravity-sensing mechanisms in plants.

scholarly journals A proposal to measure Belinfante’s curl of the spin optical force based on the Kerker conditions

2021 ◽  
Vol 136 (2) ◽  
Author(s):  
Manuel I. Marqués ◽  
Shulamit Edelstein ◽  
Pedro A. Serena
Keyword(s):  
Spin Density ◽  
Radiation Pressure ◽  
Light Field ◽  
Poynting Vector ◽  
High Refractive Index ◽  
Mechanical Action ◽  
Optical Force ◽  
Magnetic Response ◽  
Propagating Waves ◽  
Optical Configuration

AbstractThe linear momentum of electromagnetic radiation is proportional to the Poynting vector. However, when light interacts with a dipole, the radiation pressure generated is no longer proportional to the Poynting vector: the so-called Belinfante’s momentum or equivalently, the curl of the spin density of the light field, must be considered. In this paper, we propose an optical configuration, based on two evanescent counter-propagating waves, perpendicularly polarized, capable of detecting Belinfante’s mechanical action. The two beams interact with a high-refractive-index particle like silicon. The direction of the radiation pressure exerted on the particle, proportional only to the curl of the spin density, depends on the electric and magnetic response of the particle and changes sign at the radiation wavelengths corresponding with the Kerker conditions.

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