scholarly journals Lateral chirality-sorting optical forces

2015 ◽  
Vol 112 (43) ◽  
pp. 13190-13194 ◽  
Author(s):  
Amaury Hayat ◽  
J. P. Balthasar Mueller ◽  
Federico Capasso
Keyword(s):  
Wave Propagation ◽  
Angular Momentum ◽  
Field Gradient ◽  
Transverse Component ◽  
Evanescent Waves ◽  
Unusual Property ◽  
Optical Forces ◽  
Spin Angular Momentum ◽  
Absolute Strength ◽  
The Absolute

The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. Because their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces.

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.

scholarly journals Observation of acoustic spin

2019 ◽  
Vol 6 (4) ◽  
pp. 707-712 ◽  
Author(s):  
Chengzhi Shi ◽  
Rongkuo Zhao ◽  
Yang Long ◽  
Sui Yang ◽  
Yuan Wang ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Angular Momentum ◽  
Acoustic Waves ◽  
Propagation Direction ◽  
Spin Angular Momentum ◽  
Particle Rotation ◽  
Guided Mode ◽  
Pressure Fields ◽  
Metamaterial Waveguide ◽  
Spin Momentum

ABSTRACT Unlike optical waves, acoustic waves in fluids are described by scalar pressure fields, and therefore are considered spinless. Here, we demonstrate experimentally the existence of spin in acoustics. In the interference of two acoustic waves propagating perpendicularly to each other, we observed the spin angular momentum in free space as a result of the rotation of local particle velocity. We successfully measured the acoustic spin, and spin-induced torque acting on a designed lossy acoustic probe that results from absorption of the spin angular momentum. The acoustic spin is also observed in the evanescent field of a guided mode traveling along a metamaterial waveguide. We found spin–momentum locking in acoustic waves whose propagation direction is determined by the sign of spin. The observed acoustic spin could open a new door in acoustics and its applications for the control of wave propagation and particle rotation.

scholarly journals Spin angular momentum density in the tight focus of a light field with phase and polarization singularities

2019 ◽  
Vol 43 (6) ◽  
pp. 1098-1102
Author(s):  
A.A. Kovalev ◽  
V.V. Kotlyar ◽  
D.S. Kalinkina
Keyword(s):  
Angular Momentum ◽  
Light Field ◽  
Bessel Beam ◽  
Momentum Density ◽  
Transverse Component ◽  
Optical Vortices ◽  
Spin Angular Momentum ◽  
Special Cases ◽  
Order Of Magnitude ◽  
Aplanatic System

For a light field with both phase and polarization singularities at its center, expressions are obtained that describe the distribution of the spin angular momentum (SAM) density in the sharp focal spot of an aplanatic system. These expressions include the radial, azimuthal, and longitudinal SAM components. As special cases, focusing of optical vortices with radial, azimuthal, and saddle polarizations is studied. Using the Bessel beam as an example, it is shown that in some areas in the focal plane the longitudinal SAM component is zero (resulting in a photonic wheel), while in others it is an order of magnitude less than the transverse component.

Introduction of spin torques

2017 ◽  
Author(s):  
T. Kimura
Keyword(s):  
Angular Momentum ◽  
Giant Magnetoresistance ◽  
Spontaneous Magnetization ◽  
Magnetic Domain ◽  
Magnetic Multilayers ◽  
Transfer Effect ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Angular Momentum ◽  
Spin Torques

This chapter discusses the spin-transfer effect, which is described as the transfer of the spin angular momentum between the conduction electrons and the magnetization of the ferromagnet that occurs due to the conservation of the spin angular momentum. L. Berger, who introduced the concept in 1984, considered the exchange interaction between the conduction electron and the localized magnetic moment, and predicted that a magnetic domain wall can be moved by flowing the spin current. The spin-transfer effect was brought into the limelight by the progress in microfabrication techniques and the discovery of the giant magnetoresistance effect in magnetic multilayers. Berger, at the same time, separately studied the spin-transfer torque in a system similar to Slonczewski’s magnetic multilayered system and predicted spontaneous magnetization precession.

Accretion of Mass and Spin Angular Momentum by a Planet on an Eccentric Orbit

Icarus ◽  
1997 ◽  
Vol 127 (1) ◽  
pp. 65-92 ◽  
Author(s):  
Jack J. Lissauer ◽  
Alice F. Berman ◽  
Yuval Greenzweig ◽  
David M. Kary
Keyword(s):  
Angular Momentum ◽  
Spin Angular Momentum ◽  
Eccentric Orbit

scholarly journals Relation Between Star Formation and Angular Momentum in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 135-136
Author(s):  
L. Carrasco ◽  
A. Serrano
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Radial Distribution ◽  
Spiral Galaxies ◽  
Formation Rate ◽  
Inverse Function ◽  
Solar Neighborhood ◽  
Spin Angular Momentum ◽  
Stellar Formation ◽  
The Galaxy

We derive the radial distribution of the specific angular momentum j=J/M, for the gas in M31, M51 and the galaxy, objects for which well observed unsmoothed rotation curves are available in the literature. We find the specific angular momentum to be anti-correlated with the present stellar formation rate, i.e. minima of spin angular momentum correspond to the loci of spiral arms. We find that the stellar formation rate is an inverse function of j. We derive new values of Oort's A constant for the arm and interarm regions in the solar neighborhood.

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