scholarly journals Sharp focusing of a light field with polarization and phase singularities of an arbitrary order

2019 ◽  
Vol 43 (3) ◽  
pp. 337-346 ◽  
Author(s):  
V.V. Kotlyar ◽  
S.S. Stafeev ◽  
A.A. Kovalev
Keyword(s):  
Light Field ◽  
Optical Axis ◽  
Rotational Symmetry ◽  
Polarized Light ◽  
Optical Fields ◽  
Circularly Polarized Light ◽  
Sharp Focusing ◽  
Phase Singularities ◽  
Magnetic Strength ◽  
The One

Using the Richards-Wolf formalism, we obtain general expressions for all components of the electric and magnetic strength vectors near the sharp focus of an optical vortex with the topological charge m and nth-order azimuthal polarization. From these equations, simple consequences are derived for different values of m and n. If m=n>1, there is a non-zero intensity on the optical axis, like the one observed when focusing a vortex-free circularly polarized light field. If n=m+2, there is a reverse flux of light energy near the optical axis in the focal plane. The derived expressions can be used both for simulating the sharp focusing of optical fields with the double singularity (phase and polarization) and for a theoretical analysis of focal distributions of the intensity and the Poynting vector, allowing one to reveal the presence of rotational symmetry or the on-axis reverse energy flux, as well as the focal spot shape (a circle or a doughnut).

scholarly journals Multifunctional Metasurface Lens With Tunable Focus Based on Phase Transition Material

2021 ◽  
Vol 9 ◽  
Author(s):  
Yongkang Song ◽  
Weici Liu ◽  
Xiaolei Wang ◽  
Faqiang Wang ◽  
Zhongchao Wei ◽  
...  
Keyword(s):  
Phase Transition ◽  
Light Field ◽  
Focal Point ◽  
Incident Light ◽  
Polarization State ◽  
Polarized Light ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Multiple Focus ◽  
Linearly Polarized

Metasurfaces have powerful light field manipulation capabilities, which have been extensively studied in the past few years and have developed rapidly in various fields. At present, the focus of metasurface research has shifted to the tunable functionality. In this paper, a temperature-controllable multifunctional metasurface lens based on phase transition material is designed. First of all, by controlling the temperature of the desired working area and the polarization of the incident light, switching among multiple focus, single focus, and no focus at any position can be achieved, and the intensity and helicity of the output light can be adjusted. In addition, a polarization-sensitive intensity-tunable metalens based on the P-B phase principle is designed, when the incident light is linearly polarized light, left-handed circularly polarized light, or right-handed circularly polarized light, it has the same focal point but with different light field intensities. Therefore, the focused intensity can be tunable by the polarization state of the incident light.

scholarly journals Plasmonic metasurfaces manipulating the two spin components from spin–orbit interactions of light with lattice field generations

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ruirui Zhang ◽  
Manna Gu ◽  
Rui Sun ◽  
Xiangyu Zeng ◽  
Yuqin Zhang ◽  
...  
Keyword(s):  
Berry Phase ◽  
Incident Light ◽  
Polarized Light ◽  
Polarization Degree ◽  
Spin Orbit ◽  
Optical Fields ◽  
Circularly Polarized Light ◽  
Dynamic Phase ◽  
Spin Orbit Interactions ◽  
Opposite Helicity

Abstract Artificial nanostructures in metasurfaces induce strong spin–orbit interactions (SOIs), by which incident circularly polarized light can be transformed into two opposite spin components. The component with an opposite helicity to the incident light acquires a geometric phase and is used to realize the versatile functions of the metasurfaces; however, the other component, with an identical helicity, is often neglected as a diffused background. Here, by simultaneously manipulating the two spin components originating from the SOI in plasmonic metasurfaces, independent wavefields in the primary and converted spin channels are achieved; the wavefield in the primary channel is controlled by tailoring the dynamic phase, and that in the converted channel is regulated by designing the Pancharatnam–Berry phase in concurrence with the dynamic phase. The scheme is realized by generating optical lattice fields with different topologies in two spin channels, with the metasurfaces composed of metal nanoslits within six round-apertures mimicking the multi-beam interference. This study demonstrates independent optical fields in a dual-spin channel based on the SOI effect in the metasurface, which provides a higher polarization degree of freedom to modify optical properties at the subwavelength scale.

scholarly journals An orbital energy flow and a spin flow at the tight focus

2021 ◽  
Vol 45 (4) ◽  
pp. 520-524
Author(s):  
S.S. Stafeev
Keyword(s):  
Energy Flow ◽  
Optical Axis ◽  
Polarized Light ◽  
Orbital Energy ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Left Hand ◽  
Left Handed ◽  
Sharp Focus ◽  
Positive Projection

We have shown that a reverse energy flow (negative projection of the Poynting vector onto the optical axis) at the sharp focus of an optical vortex with topological charge 2 and left-hand circular polarization arises because the axial spin flow has a negative projection onto the optical axis and is greater in magnitude than positive projection onto the optical axis of the orbital energy flow (canonical energy flow). Also, using the Richards-Wolf formulas, it is shown that when focusing a left-handed circularly polarized light, in the region of the on-axis reverse energy flow, the light is right-handed circularly polarized.

scholarly journals Enhanced Chiral Mie Scattering by a Dielectric Sphere within a Superchiral Light Field

Physics ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 747-756
Author(s):  
Haifeng Hu ◽  
Qiwen Zhan
Keyword(s):  
Resonance Frequency ◽  
Matrix Method ◽  
Light Field ◽  
Polarized Light ◽  
Mie Scattering ◽  
Light Illumination ◽  
Dielectric Sphere ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
T Matrix

A superchiral field, which can generate a larger chiral signal than circularly polarized light, is a promising mechanism to improve the capability to characterize chiral objects. In this paper, Mie scattering by a chiral sphere is analyzed based on the T-matrix method. The chiral signal by circularly polarized light can be obviously enhanced due to the Mie resonances. By employing superchiral light illumination, the chiral signal is further enhanced by 46.8% at the resonance frequency. The distribution of the light field inside the sphere is calculated to explain the enhancement mechanism. The study shows that a dielectric sphere can be used as an excellent platform to study the chiroptical effects at the nanoscale.

scholarly journals Engineering phase and polarization singularity sheets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Soon Wei Daniel Lim ◽  
Joon-Suh Park ◽  
Maryna L. Meretska ◽  
Ahmed H. Dorrah ◽  
Federico Capasso
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Light Field ◽  
Optical Axis ◽  
High Symmetry ◽  
Field Phase ◽  
Phase Gradient ◽  
Matter Interaction ◽  
Phase Singularities ◽  
Light Matter Interaction

AbstractOptical phase singularities are zeros of a scalar light field. The most systematically studied class of singular fields is vortices: beams with helical wavefronts and a linear (1D) singularity along the optical axis. Beyond these common and stable 1D topologies, we show that a broader family of zero-dimensional (point) and two-dimensional (sheet) singularities can be engineered. We realize sheet singularities by maximizing the field phase gradient at the desired positions. These sheets, owning to their precise alignment requirements, would otherwise only be observed in rare scenarios with high symmetry. Furthermore, by applying an analogous procedure to the full vectorial electric field, we can engineer paraxial transverse polarization singularity sheets. As validation, we experimentally realize phase and polarization singularity sheets with heart-shaped cross-sections using metasurfaces. Singularity engineering of the dark enables new degrees of freedom for light-matter interaction and can inspire similar field topologies beyond optics, from electron beams to acoustics.

scholarly journals Tumbling and anomalous alignment of optically levitated anisotropic microparticles in chiral hollow-core photonic crystal fiber

2021 ◽  
Vol 7 (28) ◽  
pp. eabf6053
Author(s):  
Shangran Xie ◽  
Abhinav Sharma ◽  
Maria Romodina ◽  
Nicolas Y. Joly ◽  
Philip St. J. Russell
Keyword(s):  
Electric Field ◽  
Degrees Of Freedom ◽  
Optical Axis ◽  
Polarized Light ◽  
Fiber Axis ◽  
Hollow Core ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Laser Alignment ◽  
Tumbling Motion

The complex tumbling motion of spinning nonspherical objects is a topic of enduring interest, both in popular culture and in advanced scientific research. Here, we report all-optical control of the spin, precession, and nutation of vaterite microparticles levitated by counterpropagating circularly polarized laser beams guided in chiral hollow-core fiber. The circularly polarized light causes the anisotropic particles to spin about the fiber axis, while, regulated by minimization of free energy, dipole forces tend to align the extraordinary optical axis of positive uniaxial particles into the plane of rotating electric field. The end result is that, accompanied by oscillatory nutation, the optical axis reaches a stable tilt angle with respect to the plane of the electric field. The results reveal new possibilities for manipulating optical alignment through rotational degrees of freedom, with applications in the control of micromotors and microgyroscopes, laser alignment of polyatomic molecules, and study of rotational cell mechanics.

Differential polarization imaging of sickled cells

1988 ◽  
Vol 46 ◽  
pp. 62-63
Author(s):  
Marcos F. Maestre
Keyword(s):  
Optical Properties ◽  
Theoretical Approach ◽  
Polarized Light ◽  
Polarization Microscopy ◽  
Spectroscopic Techniques ◽  
Polarization Imaging ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Microscopic Scale ◽  
Chiral Structures

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.

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