Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media
TL;DR: An optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wave-front helicity controlled by the input polarization is demonstrated.
Abstract: We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wave-front helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization.
Citations
More filters
TL;DR: In this paper, the authors demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum, which provides new opportunities for increasing the data capacity of free-space optical communications links.
Abstract: Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.
3,556 citations
TL;DR: In this paper, it was shown that if every polarization vector rotates, the light has spin; if the phase structure rotates and if a light has orbital angular momentum (OAM), the light can be many times greater than the spin.
Abstract: As they travel through space, some light beams rotate. Such light beams have angular momentum. There are two particularly important ways in which a light beam can rotate: if every polarization vector rotates, the light has spin; if the phase structure rotates, the light has orbital angular momentum (OAM), which can be many times greater than the spin. Only in the past 20 years has it been realized that beams carrying OAM, which have an optical vortex along the axis, can be easily made in the laboratory. These light beams are able to spin microscopic objects, give rise to rotational frequency shifts, create new forms of imaging systems, and behave within nonlinear material to give new insights into quantum optics.
2,508 citations
TL;DR: In this paper, the authors provide an overview of the fundamental origins and important applications of the main spin-orbit interaction phenomena in modern optics that play a crucial role at subwavelength scales, including spin-Hall effects in inhomogeneous media and at optical interfaces, spindependent effects in non-paraxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces).
Abstract: This Review article provides an overview of the fundamental origins and important applications of the main spin–orbit interaction phenomena in modern optics that play a crucial role at subwavelength scales. Light carries both spin and orbital angular momentum. These dynamical properties are determined by the polarization and spatial degrees of freedom of light. Nano-optics, photonics and plasmonics tend to explore subwavelength scales and additional degrees of freedom of structured — that is, spatially inhomogeneous — optical fields. In such fields, spin and orbital properties become strongly coupled with each other. In this Review we cover the fundamental origins and important applications of the main spin–orbit interaction phenomena in optics. These include: spin-Hall effects in inhomogeneous media and at optical interfaces, spin-dependent effects in nonparaxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces) and robust spin-directional coupling via evanescent near fields. We show that spin–orbit interactions are inherent in all basic optical processes, and that they play a crucial role in modern optics.
1,642 citations
TL;DR: The concept of orbital angular momentum is now leading to new understanding of a wide range of phenomena, including fundamental processes in Bose-Einstein condensates, while the associated technologies have led to new applications in optical tweezing and microscopy as mentioned in this paper.
Abstract: Some 16 years ago, Allen et al. [Phys. Rev. A 45, 8185 (1992)] recognised that laser beams which carried an angular momentum additional to photon spin, could be realized in the laboratory. Such beams have helical phase fronts and so have an azimuthal component to the Poynting vector, which results in angular momentum along the beam axis. This orbital angular momentum, very often combined with spin to make optical angular momentum, has given rise to many developments. These range from optical spanners for driving micro-machines to high dimensional quantum entanglement and new opportunities in quantum information processing. The concept of orbital angular momentum is now leading to new understanding of a wide range of phenomena, including fundamental processes in Bose-Einstein condensates, while the associated technologies have led to new applications in optical tweezing and microscopy.
841 citations
TL;DR: Silicon-integrated optical vortex emitters are demonstrated, using angular gratings to extract light confined in whispering gallery modes with high OAM into free-space beams with well-controlled amounts of OAM, confirming the theoretical prediction that the emitted beams carry exactly defined and adjustable OAM.
Abstract: Emerging applications based on optical beams carrying orbital angular momentum (OAM) will probably require photonic integrated devices and circuits for miniaturization, improved performance, and enhanced functionality. We demonstrate silicon-integrated optical vortex emitters, using angular gratings to extract light confined in whispering gallery modes with high OAM into free-space beams with well-controlled amounts of OAM. The smallest device has a radius of 3.9 micrometers. Experimental characterization confirms the theoretical prediction that the emitted beams carry exactly defined and adjustable OAM. Fabrication of integrated arrays and demonstration of simultaneous emission of multiple identical optical vortices provide the potential for large-scale integration of optical vortex emitters on complementary metal-oxide–semiconductor compatible silicon chips for wide-ranging applications.
782 citations
References
More filters
Book•
01 Feb 1974
TL;DR: In this paper, the authors define an order parameter statistical theories of the nematic order phenomonological description of the nematic-isotopic mixtures and describe the properties of these mixtures.
Abstract: Part 1 Liquid crystals - main types and properties: introduction - what is a liquid crystal? the building blocks nematics and cholesterics smectics columnar phases more on long-, quasi-long and short-range order remarkable features of liquid crystals. Part 2 Long- and short-range order in nematics: definition of an order parameter statistical theories of the nematic order phenomonological description of the nematic-isotopic mixtures. Part 3 Static distortion in a nematic single crystal: principles of the continuum theory magnetic field effects electric field effects in an insulating nematic fluctuations in the alignment hydrostatics of nematics. Part 4 Defects and textures in nematics: observations disclination lines point disclinations walls under magnetic fields umbilics surface disclinations. Part 5 Dynamical properties of nematics: the equations of "nematodynamics" experiments measuring the Leslie co-efficients convective instabilities under electric fields molecular motions. Part 6 Cholesterics: optical properties of an ideal helix agents influencing the pitch dynamical properties textures and defects in cholesterics. Part 7 Smectics: symmetry of the main smectic phases continuum description of smectics A and C remarks on phase and precritical phenomena.
9,683 citations
TL;DR: Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum and an astigmatic optical system may be used to transform a high-order LaguERre- Gaussian mode into aHigh-order Hermite-Gaussia mode reversibly.
Abstract: Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum. An astigmatic optical system may be used to transform a high-order Laguerre-Gaussian mode into a high-order Hermite-Gaussian mode reversibly. An experiment is proposed to measure the mechanical torque induced by the transfer of orbital angular momentum associated with such a transformation.
7,918 citations
TL;DR: The transfer of information encoded as orbital angular momentum states of a light beam is demonstrated, which is resistant to eavesdropping and gives an experimental insight into the effects of aperturing and misalignment of the beam on the OAM measurement and demonstrates the uncertainty relationship for OAM.
Abstract: We demonstrate the transfer of information encoded as orbital angular momentum (OAM) states of a light beam. The transmitter and receiver units are based on spatial light modulators, which prepare or measure a laser beam in one of eight pure OAM states. We show that the information encoded in this way is resistant to eavesdropping in the sense that any attempt to sample the beam away from its axis will be subject to an angular restriction and a lateral offset, both of which result in inherent uncertainty in the measurement. This gives an experimental insight into the effects of aperturing and misalignment of the beam on the OAMmeasurement and demonstrates the uncertainty relationship for OAM.
2,230 citations
TL;DR: In this paper, it was shown that dislocations are to be expected whenever limited trains of waves, ultimately derived from the same oscillator, travel in different directions and interfere -for example in a scattering problem.
Abstract: When an ultrasonic pulse, containing, say, ten quasi-sinusoidal oscillations, is reflected in air from a rough surface, it is observed experimentally that the scattered wave train contains dislocations, which are closely analogous to those found in imperfect crystals. We show theoretically that such dislocations are to be expected whenever limited trains of waves, ultimately derived from the same oscillator, travel in different directions and interfere - for example in a scattering problem. Dispersion is not involved. Equations are given showing the detailed structure of edge, screw and mixed edge-screw dislocations, and also of parallel sets of such dislocations. Edge dislocations can glide relative to the wave train at any velocity; they can also climb, and screw dislocations can glide. Wavefront dislocations may be curved, and they may intersect; they may collide and rebound; they may annihilate each other or be created as loops or pairs. With dislocations in wave trains, unlike crystal dislocations, there is no breakdown of linearity near the centre. Mathematically they are lines along which the phase is indeterminate; this implies that the wave amplitude is zero.
1,984 citations
TL;DR: Black or reflective particles can be trapped in the dark central minimum of a doughnut laser beam produced using a high efficiency computer generated hologram to carry angular momentum transferred from the central phase singularity beam.
Abstract: Black or reflective particles can be trapped in the dark central minimum of a doughnut laser beam produced using a high efficiency computer generated hologram. Such beams carry angular momentum due to the helical wave-front structure associated with the central phase singularity even when linearly polarized. Trapped absorptive particles spin due to absorption of this angular momentum transferred from the singularity beam. The direction of spin can be reversed by changing the sign of the singularity.
1,431 citations