Polarization Plane Research Articles

Ultrafast laser texturing to improve wettability of polyimide (Kapton) films

Aim of this study is investigating the possibility of increasing the wettability of polyimide Kapton thin films by laser texturing. The laser textured surfaces were characterized through the water contact angle measurement and the surface tension evaluation; morphological and topological analyses were performed by scanning electron microscopy and atomic force microscope, respectively. As main outcome, it was found that laser texturing increases the wettability with respect to the untreated material with a decrease of contact angle of more than 20 %. In addition, the ultrashort pulse laser induced, on the material, LIPSS structures oriented in the direction of the polarization plane.

Large scale fabrication of GaN nanorods template and characterization of MOCVD grown InGaN/GaN quantum wells on [formula omitted] plane of GaN nanorods

Gallium nitride (GaN) based low-dimensional optoelectronic devices offer distinct advantages over bulk counterparts owing to enhanced surface-to-volume ratio and better strain management. Among these devices, InGaN/GaN multi-quantum wells (MQWs) based on nanostructured GaN have garnered attention due to tunable bandgap along with reduced size for its possible integration into display technology. However, to mitigate the effects of polarization induced by polar planes of GaN, such as quantum confined stark effect, researchers are exploring the growth of MQWs on non-polar planes as a practical approach to improve emission characteristics and device performance. In this work, we present the fabrication of GaN nanorods (NRs) using a two-step etching method, followed by the growth of core-shell InGaN/GaN MQWs on the exposed non-polar {101‾0} sidewalls of GaN NRs. Our metrological studies confirmed the successful growth of InGaN/GaN MQWs on the non-polar sidewalls of strain-relaxed core GaN NRs. Furthermore, power-dependent luminescence study showed emission characteristics with absence of polarization-induced effects. Cathodoluminescence study validated the emission characteristics of InGaN/GaN MQWs grown on the exposed sidewalls of the GaN NRs.

GaN micro- and nanostructures selectively grown on profiled sapphire substrates using PA-MBE without lithography

Purpose: Development of technology for the formation of ordered arrays of nanocolumns (NCs) of GaN microcrystals using plasma-activated molecular beam epitaxy from nitrogen (PA-MBE) on profiled sapphire substrates (SPS) of large diameter with a micro-cone profile. The proposed method eliminates the use of low-performance and expensive nanolithography methods. The article is aimed at a deeper understanding of the processes that determine the growth kinetics of III-N nanocolumns using PA MBE on patterned sapphire substrates with multiple orientations of various non-polar and polar planes. A new technological process for the fabrication of GaN NCs using PA-MPE is proposed, which ensures selectivity of their growth at the tops of PPS micro-cones and suppresses growth on the semipolar planes of these substrates. GaN NCs and microcrystals were grown using PA-MBE on commercially available PPS. A technology has been developed for the formation of discharged arrays of GaN nanocolumns without the use of lithographic procedures. Modes have been established that allow the formation of microcrystals and NCs with different diameters: from 30 nm to several microns. A diagram of the growth of GaN by the PA MBE method on PPS has been constructed, demonstrating the boundaries of the technological regimes for the formation of GaN NCs and microcrystals with different surface topography

Measurement of electron energetics in the equatorial and polar planes of a compact dipole plasma driven at steady state

The electron energy distribution function (EEDF) is investigated in a plasma driven at steady state and confined by a single permanent dipole magnet, employing electron cyclotron resonance heating using microwaves of 2.45 GHz. Directional retarding field energy analyzers are used to explore the EEDF in the equatorial and polar planes of the dipole magnetic field. The plasma confined in the magnetic field is found to be Maxwellian in most of the available space. Electrons have higher values of average energy () in the direction parallel to the magnetic field for both the equatorial and polar planes. The energetic electron rich regions are found at specific locations (r = 9 cm in the equatorial plane, and r = 5 cm and near the boundary region around r = 17 cm in the polar plane). The process rates such as electron neutral collisions and ionization show anisotropic variation in the polar plane of the dipole plasma.

Constraints on Early Dark Energy from Isotropic Cosmic Birefringence.

Polarization of the cosmic microwave background (CMB) is sensitive to new physics violating parity symmetry, such as the presence of a pseudoscalar "axionlike" field. Such a field may be responsible for early dark energy (EDE), which is active prior to recombination and provides a solution to the so-called Hubble tension. The EDE field coupled to photons in a parity-violating manner would rotate the plane of linear polarization of the CMB and produce a cross-correlation power spectrum of E- and B-mode polarization fields with opposite parities. In this Letter, we fit the EB power spectrum predicted by the photon-axion coupling of the EDE model with a potential V(ϕ)∝[1-cos(ϕ/f)]^{3} to polarization data from Planck. We find that the unique shape of the predicted EB power spectrum is not favored by the data and obtain a first constraint on the photon-axion coupling constant, g=(0.04±0.16)M_{Pl}^{-1} (68% C.L.), for the EDE model that best fits the CMB and galaxy clustering data. This constraint is independent of the miscalibration of polarization angles of the instrument or the polarized Galactic foreground emission. Our limit on g may have important implications for embedding EDE in fundamental physics, such as string theory.

Response of the mechanical and chiral character of ethane to ultra-fast laser pulses.

A pair of simulated left and right circularly polarized ultra-fast laser pulses of duration 20 femtoseconds that induce a mixture of excited states are applied to ethane. The response of the electron dynamics is investigated within the next generation quantum theory of atoms in molecules (NG-QTAIM) using third-generation eigenvector-trajectories which are introduced in this work. This enables an analysis of the mechanical and chiral properties of the electron dynamics of ethane without needing to subject the C-C bond to external torsions as was the case for second-generation eigenvector-trajectories. The mechanical properties, in particular, the bond-flexing and bond-torsion were found to increase depending on the plane of the applied laser pulses. The bond-flexing and bond-torsion, depending on the plane of polarization, increases or decreases after the laser pulses are switched off. This is explainable in terms of directionally-dependent effects of the long-lasting superpositions of excited states. The chiral properties correspond to the ethane molecule being classified as formally achiral consistent with previous NG-QTAIM investigations. Future planned investigations using ultra-fast circularly polarized lasers are briefly discussed.

Time-domain supersymmetry for massless scalar and electromagnetic fields in anisotropic cosmologies

It is shown that any cosmological anisotropic model produces supersymmetric theories for both massless scalar and electromagnetic (abelian) fields. This supersymmetric theory is the time-domain analogue of a supersymmetric quantum mechanics algebra theory. In this case, the variations of the anisotropic scale factors of the Universe are responsible for triggering the supersymmetry. For scalar fields, the superpartner fields evolve in two different cosmological scenarios (Universes). On the other hand, for propagating electromagnetic fields, supersymmetry is manifested through its polarization degrees of freedom in one Universe. In this case, polarization degrees of freedom of electromagnetic waves, which are orthogonal to its propagation direction, become superpartners from each other. This behavior can be measured, for example, through the rotation of the plane of polarization of cosmological light.

Single‐mode optical fibre digital decoder based on polarization using a K‐nearest neighbour algorithm

AbstractIt is shown experimentally a new digital optical decoding scheme based on the transmission or polarized light at p polarization planes using a K‐Nearest Neighbour (KNN) algorithm through a single‐mode optical fibre at 633 nm. The optical power signal is sent at p polarization planes which constitute p classes required for signal bit recognition. Results show that it is possible to recognize 32 polarizations planes, 5 bits, using 4 features corresponding to the measurement of optical power at 4 different angles at the photodetector side with an average assertiveness of 99.02%.

Villari effect in FeSe1–xSx

Acoustoelectric transformation (occurrence of electromagnetic radiation under the action of an elastic wave) in a FeSe0.925S0.075 crystal in the presence of an external magnetic field has been studied. It is shown that the application of the magnetic field along the direction of propagation of the elastic wave leads to a rotation of the plane of polarization of the emitted electromagnetic wave. The physical mechanism is that the elastic deformation leads to the appearance of a non-diagonal component of the magnetic susceptibility and to the generation of an additional alternating magnetic moment perpendicular to the external magnetic field and to the elastic displacement. The observed features are interpreted as a manifestation of the Villari effect. A phenomenological description of the experimental results is presented. The observed effect shows that the symmetry of the low-temperature FeSe1–xSx phase belongs to the triclinic syngony.

Probing the Foreshock Wave Boundary With Single Spacecraft Techniques

AbstractIn space physics, wave measurements typically use a small number of datapoints due to limited available spacecraft. Common single‐spacecraft wave vector analysis techniques built around these limitations are widely used, even in regions where the wave amplitude profile may have a strong spatial dependence. We show that in these gradient regions, the divergence‐free condition of the magnetic field requires a local modification to the plane of polarization that is incorrectly interpreted by single‐spacecraft techniques. We explore the consequences of this result in the Earth's ion foreshock using both Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun spacecraft data and a 2.5‐D hybrid Vlasov simulation conducted using the Vlasiator code. The observed foreshock ultralow frequency waves have a finite extent in the direction perpendicular to the Interplanetary Magnetic Field, and incorrect application of standard minimum variance techniques at the boundary yields a false wave vector orientation that may be used as a novel edge detection method. This method may be particularly useful for analysis of the ion foreshock at other planets where only a single spacecraft is available. More broadly, our results stand as a cautionary tale for wave analysis in other space physics contexts where the wave geometry is less clear.

Track-before-detect for bistatic radar based on pseudo-spectrum

Track-Before-Detect (TBD) is an efficient method to detect dim targets for radars. Conventional TBD usually follows an approximate motion model of the target, which may cause an inaccurate integration of the target energy. A TBD technique on basis of pseudo-spectrum in mixed coordinates adopting an accurate motion model for bistatic radar system is developed in this paper. The predicted position in bistatic polar plane is derived according to a nonlinear function that exactly describes the constant Cartesian velocity motion. Then around the predicted position, a pseudo-spectrum is formulated and its samples are accumulated to the integration frame for energy integration. The evolution of the state and the procedure of accumulation of the target energy are derived elaborately. The superior performance of the proposed method is demonstrated by some simulations.

(Invited) Photoluminescence-Based Circular Polarization Convertors for Multiplexing of Optical Information

Polarized light has a great potential to provide a variety of optical information at once such as light intensity (brightness), wavelength (color), and polarization. In particular, circularly polarized (CP) light is expected to be used not only for 3D display but also for optical data encryption and anti-counterfeiting, because the polarization plane of CP light rotates during light propagation resulting in no angular dependence on information transmission. The previously reported approaches for creating CP light from unpolarized light can be roughly classified into the filtration using a circular polarizer, the selective reflection by chiral liquid crystals, and the circularly polarized luminescence (CPL) from chiral luminophores. Meanwhile, we have recently proposed a new approach for creating highly-pure CP light by converting linearly polarized luminescence (LPL) using luminescence-based CP convertor (Figure 1a).[1] The unique advantage of the luminescence-based CP convertor lies in the spectral conversion properties of the LPL films which allows multiplexing of optical information by simply laminating LPL films. In this presentation, we introduce the multilayer-type luminescence-based CP convertors (Figure 1b) fabricated by using two or three LPL films showing different PL wavelength.In this study, we selected quantum rods (QRs) and π-conjugated luminescent polymers as one-dimensional (1D) luminophores. As a stretchable transparent polymer, poly(ethylene-co-vinyl acetate) (EVA) was used. LPL films were prepared by uniaxial stretching of the luminophore/EVA composite films. When yellow-, orange-, and red-color-emissive QRs were used as a luminophore, yellow-, orange-, and red-LPL were obtained as shown in Figures 1c-e. By laminating LPL film on the quarter-wave film with the angles between polarization plane of LPL and fast-axis of quarter-wave film were -45˚, 0˚, and +45˚, left-handed (LH-), parallel LP, and right-handed (RH-) CP light were produced, respectively. When the yellow-, orange-, and red-LPL films were laminated at three different angles (-45˚, 0˚, and +45˚) against the fast axis of the quarter-wave film, 3×3×3=27 different pieces of optical information were produced as shown in Figure 1f. Furthermore, time information on CP light can also be multiplexed theoretically by laminating several LPL films showing different fluorescence lifetimes. In this presentation, we will also discuss about time-multiplexing of optical information by multilayer-type luminescence-based CP light convertor consisting of multiple LPL films showing different PL lifetimes.[1] Y. Okazaki et. al., J. Mater. Chem. C, 2022. DOI: 10.1039/d2tc03955a. Figure 1

The rotation and incompatibility phase of the polarization state in monomode optical fibers

We have discovered two new types of geometric phases associated with a space curve in motion, considering both the arc length and time parameters, in three different scenarios. By examining the natural Bishop triad (a triad that undergoes parallel transport) and utilizing the concept of Fermi–Walker parallelism, we have identified two distinct phases known as the “Bishop incompatibility” and the “Bishop–Fermi–Walker” phases. These phases arise due to the rotational behavior along the space curve, which exhibits path dependence. We have derived the relationship between these phases for all cases. This classical approach enables us to extend the understanding of geometric rotation of the polarization plane in a monomode optical fiber without birefringence, which is situated on a moving space curve. With this extension, we can calculate the geometric phase of the rotation plane when the optical fiber’s space curve possesses an additional degree of freedom. Furthermore, we have established a connection between the Bishop incompatibility phase of the polarization state and the ordinary geometric phase of the rotation plane for the light wave as it propagates through the evolving monomode optical fiber system.

Flexible Optically Rewritable Electronic Paper

In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper are reported. The possible production of Digital Mirror Devices and the roll-to-roll process is discussed. Images on flexible e-paper are demonstrated, including bank card options. The advantages of optically rewritable e-paper technology in comparison with the e-ink usually used for this purpose are highlighted. Potential applications of flexible optically rewritable e-paper include price tags for supermarkets, indoor and outdoor advertisements, smart card labels, etc.

Demonstration of Weak Polarization Electric Field III‐N LEDs based on Polar Plane

AbstractA strong polarization electric field (PEF) in III‐nitride semiconductors has adverse effects on the performance of III‐N light‐emitting diodes (LEDs). However, to reduce the PEF of III‐N LEDs based on the polar plane (c‐plane) remains a big challenge. Here, a weak PEF blue LED on c‐plane GaN with an InGaN/AlGaN superlattices (SLs) quantum barrier and InGaN quantum well grown by metal‐organic chemical vapor deposition is proposed. The InGaN/SLs multiple quantum wells (MQWs) show a significant reduction of PEF compared with traditional InGaN/GaN MQWs. A low electric field of 0.5 MV cm−1 is obtained, which is confirmed by power‐dependent photoluminescence (PL) and time‐resolved PL measurements. The proposed LEDs with InGaN/AlGaN SLs barriers present a low efficiency droop, a great wavelength stability, and a high −3 dB E‐O modulation bandwidth up to 1.01 GHz. This work demonstrates the role of InGaN/AlGaN SLs barriers in reducing the PEF of III‐N LEDs and provides a feasible technical route to achieve the weak PEF LEDs on c‐plane, which can be expanded and applied to the preparation of high‐performance, long wavelength, and deep UV III‐N LEDs.

Determination of the polarization plane specific rotation in gyrotropic crystals of the middle category by the spectrophotometric method

A large number of modern functional single crystals of the middle category belong to gyrotropic media. In these crystals, when light propagates along the optical axis, rotation of the plane of its polarization is observed. In this work a spectrophotometric method was used to obtain the dispersion dependences of the rotation angle of the polarization plane. This method is based on measuring the intensity of light passing through the polarizer–crystal–analyzer system, the crystal is a polished plane-parallel plate of a uniaxial gyrotropic crystal cut perpendicular to the optical axis. Measurements were carried out on a UV-Vis-NIR spectrophotometer Cary-5000 in the wavelength range of 200—1200 nm using polarizers — Glan–Taylor prisms. Polished plane-parallel plates of known SiO2 and α-LiIO3 crystals were used as samples. The obtained dispersion dependences of the spectral transmission coefficients are oscillating. Discrete values of the specific angles of rotation of the plane of polarization of light are calculated from the extremes on these dependencies. These discrete values can be approximated by the formulas Drude, Chandrasekhar and Vyshina, depending on what determines the nature of the rotational ability of the plane of polarization of light in each particular material. For the studied crystals, dependences of the modified Drude formula of the form 1/ρ = f(λ2) are plotted, these dependences should have a linear character in the case of an ideal crystal. The obtained experimental results correlate well with the available literature data. The advantages of this method are efficiency, the possibility of obtaining dispersion dependences of the specific rotation angle of the polarization plane, the need for a single sample, the possibility of assessing the nature of the rotational ability of specific crystals, the possibility of evaluating the structural perfection of the studied crystals.

Attosecond metrology in circular polarization

Attosecond metrology with linearly polarized light pulses is the basis of a highly successful research area. An even broader impact can be expected from a generalized metrology that covers two-dimensional polarization states, enabling notably the study of chiroptical phenomena on the electronic time scale. Here, we introduce and demonstrate a comprehensive approach to the generation and complete characterization of elliptically to circularly polarized attosecond pulses. The generation relies on a plug-in device of unprecedented simplicity. For the characterization, we introduce Stokes-parameter and attosecond-resolved reconstruction of optical waveforms (SPARROW), which encodes the attosecond-metrology information into the photoemission angle in the polarization plane and accesses all four Stokes parameters of the attosecond pulses. Our study demonstrates a physically transparent scheme for attosecond metrology with elliptical to fully circular polarizations, applicable to both table-top and accelerator-based light sources, which will unlock studies of chiral molecules, magnetic materials, and novel chiroptical phenomena on the most fundamental time scales.

Optoelectronic properties of rare earth materials from first principles calculations: EuMnO3 versus GdMnO3

The electronic band structure, density of states, complex dielectric function, and optical absorption of orthorhombic ReMnO3 were investigated using the density functional theory formalism, considering the local density approximation. In the range between 200 and 230 nm, approximately, optical absorption decreases. However, starting from 230 nm to larger wavelengths, the optical absorption increases more quickly due to the appearance of transitions involving mainly O-2p states, toward Eu-4f and Gd-4f states. Finally, the complex dielectric function and the optical absorption of ReMnO3 were shown to be sensitive to the plane of polarization of the incident light.

Exchange effects in strong-field ionization of the excited lithium ion induced by one- and two-component laser fields

Spin-dependent effects in strong-laser-field-induced above-threshold ionization of excited Li+ ions, caused by the requirement that the electron wave function is antisymmetric, are analyzed using the strong-field approximation and saddle-point method. For an excited Li+ ion exposed to a linearly polarized laser field, the minima in the photoelectron momentum distribution in the polarization plane appear if the excited Li+ ion state is the spin singlet state, while for the spin triplet state these minima are absent. The difference between the spectra obtained with these spin states is quantified by the corresponding normalized difference of the differential ionization probabilities. Employing the saddle-point method, we show that, for the spin singlet state, all relevant contributions to the differential ionization probability exhibit minima for approximately the same values of the photoelectron energy and emission angle, thus leading to the minima in the total spectra. Similar conclusions hold for a bicircular driving field. In this case, the range of values of the photoelectron energy and emission angle for which different saddle-point contributions exhibit minima is almost the same for all saddle-point solutions. This is particularly true for the high-energy part of the spectrum, and the minima are more pronounced than for the linearly polarized driving field case. In order to check whether these minima can be detected in an experiment, we perform focal averaging, which takes into account the intensity distribution in the laser focus. For both linearly polarized and bicircular driving fields, the minima survive the focal-averaging procedure. They are slightly blurred in the former case, while in the latter case the focal averaging almost does not affect the minima at all. Finally, we confirm that similar conclusions hold for the photoelectron velocity maps in the plane that contains the laser-field propagation direction.

AUTOMATIC MODULATION CLASSIFICATION USING DEEP LEARNING POLAR FEATURE

The automatic modulation classification of signals is of great importance in modern communications, especially on cognitive radio. Several methods have been used in this field, the most important of which is the classification of modulation automatically using Deep Learning, where the methods depend on the convolution neural network, which is one of the Deep Learning networks, achieved high accuracy in classifying the modulation, so the proposed network depends on the type of deep learning CNN consisting of four blocks, each block contains a set of symmetric and asymmetric filters. The network also contains Max Pool. In this paper, the features extracted in phase-squaring and polar have been combined for the input, which helps in extending the input, that is, an increase in the features inside the network. It also contributes to improving the accuracy of classifying the higher-order modulation through the Polar plane. The dataset RadioML 2018.01A was adopted, which is used in the most recent research, where 11 types of modulation normal-class: (FM, GMSK, QPSK, BPSK, 0QPSK, AM-SSB-SC, 4ASK, AM-DSB-SC, 16QAM, 8PSK,00K) were taken. A simulation of which can be found in Matlab 2021. The proposed network achieved 100% classification accuracy when the signal-to-noise ratio is greater or equal to 2 dB for 11 types of modulation. The results of the paper were compared with modern networks Baseline network, Visual Geometry Group network, and Residual Neural network. The comparison showed the superiority of the proposed network over these networks, as the proposed network achieved an accuracy equal to 100% at SNR 2 dB while BL achieved an accuracy equal to 72% at SNR 2 dB, RN, and VGG almost reach 93% at SNR 2 dB.