Polarization State Of Radiation Research Articles

Магнито-оптическая чувствительность spun-волокна при наличии осевого механического скручивания

The polarization state of light radiation in a spun fiber is one of the factors determining its magneto-optical sensitivity and application in current sensors. In the article, the effect of elastic twisting around the spun fiber axis on the evolution of radiation polarization and the sensitivity of the fiber is studied by modeling. It has been found that twisting effects or other effects that change the spiral pitch lead to degradation of the sensitivity of the spun fiber, and the amount of degradation is determined by the state of polarization at the input of the disturbed fiber section. It is shown that when returning to the non-stressed state with the initial parameters, the sensitivity of the fiber does not recover, but continues to decrease. The importance of minimizing twisted sections in the practical application of spun fiber in a current sensor is noted.

Development of a polarimetric thermal imager calibration method

Measurement of thermal imager characteristics is important for the reliable and efficient operation of the device in various fields, including science, medicine, and industry. Incorrect measurements can lead to errors, which can be critical, especially for military-grade thermal imagers.
 This article is dedicated to developing a method for monitoring the output parameters of polarimetric thermal imagers based on calibration. During calibration, the following operations are proposed: visual inspection, functionality check, measurement of polarimetric thermal imager parameters, and evaluation of measurement uncertainties. In this article, the controlled parameters of the polarimetric thermal imager are the measured for device temperature and NETD, Noise Equivalent Temperature Difference. For these parameters, a measurement model, a measurement function, and an uncertainty budget have been developed. The uncertainty budget includes only the main and most influential uncertainty components. This methodology can only be used for one type of polarimetric thermal imager, where the determination of the radiation polarization state is achieved by rotating a phase plate.

Polarization independent lattice-coupled terahertz toroidal excitation

The toroidal dipole excitation is important for metamaterial research because of its low-loss attribute. In this study, we demonstrate numerically and experimentally, a unique toroidal metasurface that modulates a broad resonance into a sharp mode, independent of the polarization of the incident terahertz (THz) radiation, by coupling the inherent toroidal dipole excitation to the lattice mode of the metasurface. The advantage of polarization independence enables the excitation of ‘lattice-coupled toroidal mode’ for both the orthogonally polarized states of the incident THz radiation in the metasurface. The interaction of the two resonances results in the enhancement of the quality factor of the metasurface at the point of resonance matching. The surface current profile as well as multipole analysis of scattered powers by electric, magnetic, and toroidal dipoles confirm the domineering effect of toroidal dipole excitation for both the polarization states of incident THz radiation. Such a lattice-matched toroidal excitation-based device has the potential to impact the development of polarization-independent THz components for ultrasensitive sensors, lattice-enhanced equipment, and slow light devices for light–matter interaction.

Perfect linear polarization wave generator based on quasi-bound states in the continuum.

Quasi-bound states in the continuum (q-BICs) in optical metasurfaces have been found to carry special radiation polarization properties. Herein, we have studied the relationship between the radiation polarization state of a q-BIC and the polarization state of the output wave, and theoretically proposed a perfect linear polarization wave generator controlled by the q-BIC. The proposed q-BIC has an x-polarized radiation state, and the y co-polarized output wave is completely eliminated by introducing additional resonance at the q-BIC frequency. Finally, a perfect x-polarized transmission wave with very low background scattering is obtained, and the transmission polarization state is not limited by the incident polarization state. The device can be used to efficiently obtain narrowband linearly polarized waves from non-polarized waves, and can also be used for polarization-sensitive high-performance spatial filtering.

Rotationally Symmetrical Spoof-Plasmon Antenna for Polarization-Independent Radiation Enhancement

Plasmon antennas allow subwavelength confinement and enhancement of electromagnetic fields at the ``hotspot'' where the radiation efficiency of emitters can be substantially enhanced. Such enhancement, however, is often polarization dependent. Consequently, the radiation behaviors (e.g., radiation pattern and polarization states) of the emitter placed at the hotspot are also modified significantly. Enhancing the radiation efficiency without altering the original radiation pattern and polarization state of the emitter is highly desired for many sought-after applications involving chiral emitters but remains a challenging task, especially at low frequencies. To this end, spoof-plasmon antennas with fourfold and sixfold rotational symmetries are designed and realized experimentally. These plasmon antennas support polarization-independent localized plasmon resonances, which can significantly enhance the local density of photonic states at the structural center without changing the polarization state of the emitter. As a typical example, the structure with sixfold rotational symmetry is coupled with a half-wave dipole antenna. The measurement results show that the far-field radiation pattern of the dipole antenna is maintained with the radiation efficiency enhanced by more than 2 orders of magnitude, irrespective of the dipole orientation.

Generation of Multiple Vector Optical Bottle Beams

We propose binary diffractive optical elements, combining several axicons of different types (axis-symmetrical and spiral), for the generation of a 3D intensity distribution in the form of multiple vector optical ‘bottle’ beams, which can be tailored by a change in the polarization state of the illumination radiation. The spatial dynamics of the obtained intensity distribution with different polarization states (circular and cylindrical of various orders) were investigated in paraxial mode numerically and experimentally. The designed binary axicons were manufactured using the e-beam lithography technique. The proposed combinations of optical elements can be used for the generation of vector optical traps in the field of laser trapping and manipulation, as well as for performing the spatial transformation of the polarization state of laser radiation, which is crucial in the field of laser-matter interaction for the generation of special morphologies of laser-induced periodic surface structures.

Birefringence of orthorhombic DyScO3: Toward a terahertz quarter-wave plate

With growing interest in exploring fundamental phenomena at terahertz (THz) frequencies, the need for controlling the polarization state of THz radiation is indispensable. However, simple optical elements, such as waveplates that allow creating circularly-polarized THz radiation, are scarce. Here, we present THz quarter-wave plates (QWPs) made out of (110)-cut and (001)-cut DyScO3 (DSO) crystals. We examine the complex refractive indices along the in-plane axes and map the birefringence of both DSO crystals. Further, we demonstrate that both 50-μm-thick (110)-cut DSO and 370-μm-thick (001)-cut DSO crystals behave like a QWP over a broad frequency range of 0.50–0.70 THz and 0.50–0.61 THz, respectively, with a phase tolerance of ±3%.

Third optical harmonic generation reveals circular anisotropy in tilted silicon nanowire array.

In this Letter, we report on the circular anisotropy of third-harmonic (TH) generation in an array of silicon nanowires (SiNWs) of approximately 100 nm in diameter tilted to the crystalline silicon substrate at an angle of 45°. Numerical simulations of the scattering at the fundamental and TH frequencies of circularly polarized light by a single SiNW and an ansatz structure composed of 13 SiNWs used as a geometrical approximation of the real SiNW array indicate asymmetric scattering diagrams, which is a manifestation of the photonic spin Hall effect mediated by the synthetic gauge field arising due to the special guided-like mode structure in each SiNW. Despite strong light scattering in the SiNW array, the experimentally measured TH signal demonstrated significant dependence on the polarization state of incident radiation and the SiNW array spacial orientation in regard to the wave vector direction.

Model of the spectral dependence of changes in the polarization state of laser radiation in magneto-optical crystal in the presence of multiple reflections from its faces

In this work we investigated the phenomena in the Faraday rotator that can affect the polarization state of transmitting laser radiation. We have found that multiple reflections of radiation from the faces of the terbium gallium garnet (TGG) crystal can cause deterioration of radiation extinction ratio and, therefore, isolation properties of Faraday cell. We were able to calculate the impact of this factor on polarization extinction ratio of monochromatic and quasimonochromatic laser radiation transmitting through the crystal.

Thermal lens astigmatism in glass and in cubic crystals with [001] orientation.

The thermal lens was investigated in CaF2 and Tb3Ga5O12 cubic crystals with [001] crystallographic axes orientation and in magneto-optical glass MOG103 by the method of phase-shifting interferometry. It was demonstrated experimentally that the thermal lens has astigmatism determined by the incident radiation polarization state and by the optical anisotropy parameter ξ. A method of ξ determination by measuring thermal lens astigmatism in cubic crystals with [001] orientation was proposed and verified. It was shown that thermally induced depolarization and the amplitude of phase astigmatism depend on the position of the crystal with [001] orientation in antiphase.

Quantum Tomograph for Measurement and Characterization of Quantum States of Biphoton Sources

The development of methods and devices for measuring the quantum states of photon fluxes is a matter of current interest. In this paper, we propose a prototype device for characterizing biphoton light sources using quantum tomography based on spontaneous parametric down-conversion. This prototype device is an experimental implementation of a specialized quantum tomograph designed to measure the quantum polarization states of radiation generated by biphoton sources. In this article, we present the operational principle of the device for characterizing biphoton light sources and describe our specially developed software that enables determination of the statistical characteristics of the measured quantum state, calculation of the tomographic and most probable estimates of the density matrix, and the measurement errors of the density matrix elements, as well as evaluation of the quality of the quantum state of the biphotons.

Quantum tomograph for measurement and characterization of quantum states of biphoton sources

The method and prototype of a device for characterizing of biphoton light sources based on spontaneous parametric downdonversion by quantum tomography are described. The prototype is an experimental implementation of a specialized quantum tomograph designed to measure the quantum polarization states of radiation generated by biphoton sources. Specially developed software will determine the statistical characteristics of the measured quantum state, calculate the tomographic and likelihood estimations of the density matrix, calculate the measurement errors of the density matrix elements and evaluate the quality of the quantum state of biphotons.

Graphene-based optically tunable structure for terahertz polarization control

We present a theoretical model of optically tunable graphene-based structure for polarization characteristics control of transmitted terahertz (THz) wave. The experimental verification was performed using a THz time-domain polarimetry setup. The tunability is achieved by applying an external optical pumping and magnetic field. The structure shows the possibility for dynamical control of ellipticity and azimuth angles of polarization state of THz radiation in a transmission mode. This study indicates a strong potential for using graphene-based structures for polarization sensitive applications such as THz wireless communications and biomedical research.

Undulator configuration for helicity switching in in-vacuum undulators

We propose a new scheme to control the polarization state of undulator radiation, in which the helicity of circularly polarized radiation can be switched by translating the whole undulator along the horizontal direction. This is in contrast to the conventional method based on a phasing operation (longitudinal motion of magnetic arrays), which gives rise to a large variation of the three-dimensional magnetic force acting on the magnetic array. Because the mechanical design can be much simpler than conventional undulators equipped with a function for the phasing operation, the proposed scheme is well compatible with in-vacuum undulators. Numerical and experimental studies were carried out to reveal the performance and feasibility of the proposed scheme, showing its potential as an attractive option for the in-vacuum undulators.

Spectral and polarization characteristics of X-ray hybrid radiation

Vavilov-Cherenkov emission and transition radiation are the well-known phenomena and find a broad application for different scientific communities. In the case of simultaneous generation of both types of radiation, there is a possibility of interference between radiation fields. Thus, the emitted radiation could possess both transition radiation and Vavilov-Cherenkov radiation properties, that is why it should be considered as hybrid radiation. In this paper, we present the results of the theoretical investigation of X-ray hybrid radiation. Using the polarization current approach and the atomic scattering factor formalism to account anomalous dispersion of the complex permittivity we study spectral-angular distributions and polarization states of X-ray hybrid radiation when a charge obliquely falls on a foil. The theoretical results greatly contribute to understanding of X-ray Vavilov-Cherenkov radiation as well as the development of the X-ray narrow band radiation sources based on Vavilov-Cherenkov effect.

The specifics of single-mode laser modules application in optical-electronic complexes based on light scattering

The polarization state of edge-emitting single-mode laser modules radiation and their conditions of using in laser measuring systems of scattered radiation diagnosis are considered. For laser modules from two batches, both the polarization degree of collimated radiation and polarization degree spatial dependence in two orthogonal planes when there is no collimation are measured. It is established the angular dependence of non-collimated radiation polarization degree at different planes is various. We also considered the impact laser diodes degradation on these dependencies. It is shown that while exploitation of single-mode laser diodes in laser systems for scattered radiation characteristics researching it is needed to make control the polarization state of their radiation while service.

Leaky-Wave Radiations with Arbitrarily Customizable Polarizations Based on Spoof Surface Plasmon Polaritons

Leaky-wave antennas (LWAs), which exploit traveling waves with phase velocity greater than the speed of light, have attracted much attention for their miniaturizability and easy fabrication. However, the polarization states of leaky-wave radiation are generally hard to design at will. This study presents a spoof-surface-plasmon waveguide with bilateral tilted grooves to tailor the polarization of its emission. The design is simple and feasible for realizing arbitrary polarization of leaky waves, just by changing the relative displacement of grooves on either side of the waveguide, and is expected to impact advanced microwave circuits and antennas.

Spatiotemporal dynamics of the polarisation state of laser radiation performed by lens-axicon combinations

Spatiotemporal dynamics of the polarisation state of laser radiation performed by lens-axicon combinations were investigated theoretically and numerically in the paraxial regime. We demonstrate that in this case, while the static polarisation state does not change, various features are observed in the temporal dynamics, including spiral trajectories of the field components, transformation of the polarisation state and the “disappearance” of the light field at some time moments of the harmonic period. The results obtained can be useful for understanding the effects of spatiotemporal polarisation transformations of laser radiation, which is crucial in the field of ultrastrong and ultrashort laser-matter interactions.

Strongly Magnetized Sources: QED and X-ray Polarization

Radiative corrections of quantum electrodynamics cause a vacuum threaded by a magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources, the difference in speed is small. However, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.

Visible frequency plasmonic perfect absorber made of a thin metal layer containing cylindrical grooves

In this communication, a visible frequency plasmonic perfect absorber (PPA) made of a thin metal layer (gold and aluminum) with an array of cylindrical grooves is demonstrated and studied numerically using the finite difference time domain solver. A novel design concept is used to achieve perfect absorption at tunable wavelengths between 400 and 1000 nm. The PPA unit cell is made of a cylindrical groove of appropriate depth, and the size of the groove is typically set to half the array period. By simply changing the array period, the perfect absorption (100%) spectral position is set to a desired wavelength. The PPA is observed to be very effective for wide incident angles and polarization states of input radiation. The study reports an attractive alternative way of designing all-metal-based PPA that may have potentials for various plasmonic and photonic applications.