Polarization Angle Research Articles

Simultaneous vector magnetometry based on fluorescence polarization of NV centers ensemble in diamond

The nitrogen-vacancy (NV) centers ensemble has extensive application prospects in vector-magnetic-field measurement due to its accurate and fixed spatial orientations along the crystallographic axes of diamonds. However, to address signals of NV centers along all four axes, a large bias magnetic field sufficient to spectrally separate their resonances is typically inevitable, which may affect the magnetic substance under test and require multiple-frequency microwaves to interrogate signals of the four axes. Here, we demonstrate an NV-based simultaneous vector magnetometer that works at a bias field as low as just separating the resonant peaks of |ms=±1 states and utilizes a single-frequency microwave. By simultaneously detecting the fluorescence at specific optical polarization angles in three orthogonal directions and determining the transformation matrix in advance, all the Cartesian components of the magnetic field under test are distinguished. The experimentally achieved magnetic-field sensitivity is 63 nT/Hz, and the bias field is reduced to around 11 Gauss (still reducible by narrowing the linewidth) in ambient conditions. The proposed methods dramatically reduce the bias field for NV-based simultaneous vector magnetometers and potentially expand their applications in biological science, materials science, and industrial noninvasive detection.

Horizontal aluminum magneto-plasmonic metasurface for efficient magneto-optical Kerr modulation and sensing in the ultraviolet range.

Most of the plasmonic nanostructures utilized for magneto-optical (MO) enhancement have been limited to noble metals with resulting enhancement in the visible and infrared spectral range. Here, we designed a horizontal aluminum magneto-plasmonic metasurface, with the ability to control the Kerr rotation angle and enhance the RI sensing performance based on magneto-plasmons, by exploiting the polarization degree of freedom in the ultraviolet range. The surface composes of L-shaped magnetic dielectric embedded in the Al film. The reflection spectrum and the Kerr rotation angle map are both symmetric about the polarization angle of 45° and 135°. It is demonstrated that the sign change of the two maximal Kerr rotation angles at polarization angle of 0° and 90°, originates from the relative contribution of the two mutually orthogonal oscillating electric dipoles. In addition, the RI sensing FoM based on Kerr reversal at 372 nm of this structure reaches 5000/RIU, which is superior to the result in the visible or infrared range (1735/RIU). The results of our investigation demonstrate the potential of Al-based magneto-plasmonic effect and offer opportunities to push the MO spectral response out of the visible range into the ultraviolet range.

High-Q all-dielectric metasurface perfect absorber powered by quasi-bound states in the continuum

All-dielectric perfect absorbers powered by quasi-bound states in the continuum (-BIC) are of great importance for developing high-performance optoelectronic devices because they provide high Q-factor absorption. However, these structures usually require the addition of metal back reflectors or degenerate critical coupling to achieve high absorption, which often introduces problems such as Joule heat output and sensitivity to geometrical parameters. In this work, we present an all-dielectric high Q-factor metasurface perfect absorber (MPA) with a cell structure consisting of split Si elliptical disks. By adjusting the tilt angle of the gap, the metasurface can excite a single quasi-BIC resonance in a highly reflective background, corresponding to the electric quadrupole (EQ) mode. Due to the asymmetric coupling of the EQ mode, the proposed metasurface easily breaks the 50% absorption limit. At the wavelength of 894.645 nm, the metasurface achieves a perfect absorption of more than 99% and has a Q-factor of up to 1955. In addition, the structure shows excellent tolerance to geometrical parameters while ensuring high absorption performance. By adjusting the polarization angle, we have also achieved an arbitrary tuning of the absorption efficiency without frequency shift. This work provides a viable scheme for the design of tunable, large-tolerance, and high-Q all-dielectric MPAs, which have a broad potential application in the fields of optical filtering, optical switching, and polarization detection.

A Novel Sensing Method to Detect Malachite Green Contaminant on Silicon Substrate Using Nonlinear Optics.

We propose a nonlinear-optics-based nanosensor to detect malachite green (MG) contaminants on semiconductor interfaces such as silicon (Si). Applying the simplified bond hyperpolarizability model (SBHM), we simplified the second-harmonic generation (SHG) analysis of an MG-Si(111) surface and were able to validate our model by reproducing experimental rotational anisotropy (RA) SHG experiments. For the first time, density functional theory (DFT) calculations using ultrasoft pseudopotentials were implemented to obtain the molecular configuration and bond vector orientation required by the SBHM to investigate and predict the second-harmonic generation contribution for an MG-Si 001 surface. We show that the SBHM model significantly reduces the number of independent components in the nonlinear tensor of the MG-Si(111) interface, opening up the possibility for real-time and non-destructive contaminant detection at the nanoscale. In addition, we derive an explicit formula for the SHG far field, demonstrating its applicability for various input polarization angles. Finally, an RASHG signal can be enhanced through a simulated photonic crystal cavity up to 4000 times for more sensitivity of detection. Our work can stimulate more exploration using nonlinear optical methods to detect and analyze surface-bound contaminants, which is beneficial for environmental monitoring, especially for mitigating pollution from textile dyes, and underscores the role of nonlinear optics in real-time ambient-condition applications.

Generation of arbitrarily patterned polarizers using 2-photon polymerization

Patterned polarizers are prepared using liquid crystals (LC) doped with a black dichroic dye and in combination with a linear polarizer. The pattern is achieved with a nanostructured LC alignment surface, that is generated using a two-photon polymerization direct laser write (2PP-DLW). This technique creates a pattern of high-resolution grooves in the photoresist at any arbitrary angle. The angle governs the LC orientation at any substrate surface point, determining the transmitted light linear polarization angle. This paper presents the first use of a 2PP-DLW cured positive tone photoresist for dichroic dye-doped LC alignment. Two complementary photoresists have been employed: conventional negative tone SU-8 photoresist and, in this context novel, positive tone S1805 photoresist. The alignment quality of the polarizers has been assessed by analyzing the transmission using an additional polarizer. For SU-8, the resulting grayscale pattern and a contrast ratio (CR) of 14 has measured. The uniformity of the alignment has been measured to be 65% using normalized Shannon entropy (H). For S1805, a CR of 37 was measured, and a uniformity of 63% was obtained. 2PP-DLW allows for shaping complex patterns in submicron dimensions and for the fabrication of arbitrarily patterned polarizers and other LC devices.

Polarization Degree of Magnetic Field Structure Changes Caused by Random Magnetic Field in Gamma-Ray Burst

In a Poynting-flux-dominated jet that exhibits an ordered magnetic field, a transition toward turbulence and magnetic disorder follows after magnetic reconnection and energy dissipation during the prompt emission phase. In this process, the configuration of the magnetic field evolves with time, rendering it impossible to entirely categorize the magnetic field as ordered. Therefore, we assumed a crude model that incorporates a random magnetic field and an ordered magnetic field, and takes into account the proportionality of the random magnetic field strength to the ordered magnetic field, in order to compute the polarization degree (PD) curve for an individual pulse. It has been discovered that the random magnetic field has a significant impact on the PD results of the low-energy X-ray. In an ordered magnetic field, the X-ray segment maintains a significant PD compared to those in the hundreds of keV and MeV ranges even after electron injection ceases, making PD easier to detect by polarimetry. However, when the random magnetic field is introduced, the low-energy and high-energy PDs exhibit a similar trend, with the X-ray PD being lower than that of the high-energy segment. Of course, this is related to the rate of disorder in the magnetic field. Additionally, there are two rotations of the polarization angles (PAs) that were not present previously, and the rotation of the PA in the high-energy segment occurs slightly earlier. These results are unrelated to the structure of the ordered magnetic field.

Large-Area Perovskite Nanocrystal Metasurfaces for Direction-Tunable Lasing.

Perovskite nanocrystals (PNCs) are attractive emissive materials for developing compact lasers. However, manipulation of PNC laser directionality has been difficult, which limits their usage in photonic devices that require on-demand tunability. Here we demonstrate PNC metasurface lasers with engineered emission angles. We fabricated millimeter-scale CsPbBr3 PNC metasurfaces using an all-solution-processing technique based on soft nanoimprinting lithography. By designing band-edge photonic modes at the high-symmetry X point of the reciprocal lattice, we achieved four linearly polarized lasing beams along a polar angle of ∼30° under optical pumping. The device architecture further allows tuning of the lasing emission angles to 0° and ∼50°, respectively, by adjusting the PNC thickness to shift other high-symmetry points (Γ and M) to the PNC emission wavelength range. Our laser design strategies offer prospects for applications in directional optical antennas and detectors, 3D laser projection displays, and multichannel visible light communication.

Detecting axion dark matter with black hole polarimetry

The axion, as a leading dark matter candidate, is the target of many ongoing and proposed experimental searches based on its coupling to photons. Ultralight axions that couple to photons can also cause polarization rotation of light which can be probed by the cosmic microwave background. In this work, we show that a large axion field is inevitably developed around black holes due to the Bose-Einstein condensation of axions, enhancing the induced birefringence effects. Therefore, measuring the modulation of supermassive black hole imaging polarization angles is a strong probe to the axion-photon coupling due to the formation of the axion condensation (axion star) which enhances the axion field. The oscillating axion field around black holes induces polarization rotation on the black hole image, which is detectable and distinguishable from astrophysical effects on the polarization angle, as it exhibits distinctive temporal variability and frequency invariability. In this work, we perform the theoretical calculation on the axion star formation rate and correspondingly the enhanced axion field value near supermassive black holes. Then, we present the range of axion-photon couplings within the axion mass range 10−21–10−16 eV that can be probed by the Event Horizon Telescope. The axion parameter space probed by black hole polarimetry will expand with the improvement in sensitivity on the polarization measurement and more black hole polarimetry targets with determined black hole masses. Published by the American Physical Society 2024

Broadband Unidirectional Thermal Emission

AbstractDirectional control of far‐field thermal emission plays a key role in effective heat and energy transfer. However, conventional photonic strategies are challenging to concurrently control the polar and azimuthal angle of thermal emission over broadband. Here both polar and azimuthal angles of thermal emission are constrained to narrow ranges over broadband by introducing in‐plane anisotropy combined with magneto‐optical materials in the epsilon‐near‐zero (ENZ) wavelength range. The physical mechanism of tunable perfect absorption/emission is explored by investigating the evolution of multiple topological phase singularity pairs (TPSPs). The structure consisting of a magnetized gradient‐ENZ emitter and anisotropic spacer that exhibits high (>0.8) unidirectional emissivity (θ: 55°–79°, φ: 163.5°–196.5°) in the p‐polarization for a broad range of wavelength (22–26 µm) is demonstrated. The unveiled physics synergizing ENZ, anisotropy, and magneto‐optical properties that support broadband unidirectional thermal emission will bring new opportunities in applications such as thermal camouflaging, thermal photovoltaics, and infrared light sources.

Hybrid Anapole Induced Chirality in Metasurfaces.

The interaction between light and matter, particularly chirality, plays a pivotal role in modern science and technology. Typically, metasurfaces achieve chiro-optical effects by coupling electric and magnetic dipoles in specific orientations. In this work, the design and optimization of an asymmetric H-shaped metasurface is explored to induce hybrid anapole (HA) for optical activity. When the symmetry of the metasurface structure is disrupted, the design can simultaneously excite first-order and pseudo high-order HA under illumination with a specific circular polarization, both occurring within the same spectral regime. This results in high reflection for one circular polarization and a significant reduction in reflection for the orthogonal polarization, thereby exhibiting exceptional chiro-optical activity. Moreover, the HA-based chiral metasurface demonstrates strong polarization control capabilities, as verified by Stokes parameter analysis, revealing high birefringence and a pronounced dependence on the incident polarization angle. These results provide valuable insights for the design and optimization of HA metasurfaces for advanced optical applications and polarization control, paving the way for new developments in chiral nanophotonics.

The excellent electrocatalytic HER activity and photogalvanic effect of WS2/Ga2O3 based on Density Functional Theory

This study is based on density functional theory, studied structure and electronic properties, optical properties, electrocatalytic water splitting to produce H2, and electrical properties of the WS2/Ga2O3 heterojunction. By analyzing the photoelectric characteristics, we find that the WS2/Ga2O3 heterojunction has built-in electric field, which can separate photogenerated carriers and effectively capture visible light for visible light photocatalysis. In addition, the change of Gibb free energy (ΔG) tends to 0, so when the WS2/Ga2O3 heterojunction is used as a catalyst, the hydrogen evolution reaction tends to proceed spontaneously. Interestingly, by analyzing the electrical properties, we find that the large and obviously changed photogalvanic effect photocurrent is produced with the change of polarization angle and photon energy of the WS2/Ga2O3 heterojunction, and it has the potential to become high-sensitivity optoelectronic detector.

Scattering characteristics of dual counter-propagation high-order circularly symmetric Bessel beam by a multilayer chiral sphere

The interaction between dual counter-propagating high-order circularly symmetric Bessel beams (CSBBs) and multi-layered chiral particles is investigated. Within the framework of generalized Lorenz-Mie theory (GLMT), the distribution characteristics of the superposition of two beams are studied based on the vector superposition theorem. The near-field, internal field, and far-field radar cross section (RCS) of the dual-layered chiral sphere illuminated by dual CSBBs are obtained according to the boundary conditions. By comparing the results of RCS with those from the references for two cases: first, when CSBBs degenerate into plane waves incident on multi-layered chiral sphere, and second, when Bessel beams illuminate isotropic multi-layer sphere degenerated by chiral multi-layered sphere, the effectiveness of the principle and program exhibited here is confirmed. The impact of various parameters on the distribution of the superposed field, the near-field, internal field, and far-field RCS of the particles are analyzed in detail, such as the order, half-cone angle, incidence angle, and polarization angle. The research results in this paper provide theoretical assistance for understanding the interaction between dual CSBBs and non-uniform chiral multi-layered particles and have important value in realizing optical manipulation of complex chiral layered particles.

Robust Multi-Band DNG metamaterial absorber for GPS (L1), ISM, and 5G application with Enhanced polarization and angle stability

This research introduces a triple-band metamaterial absorber characterized by insensitivity to both polarization and incident angles. The structure includes square ring resonators on the upper side and a continuous metal ground on the lower side, separated by an FR4 substrate. At the lowest operating frequency, the unit cell’s thickness, and length measure 0.0128λ and 0.156λ, respectively. Under normal incidence, the proposed absorber demonstrates three clear absorption peaks at 1.56, 2.43, and 3.36 GHz, achieving absorption rates of 98 %, 99 %, and 97 %, respectively. The absorption response exhibits variation with incident angles up to 70° for both TM and TE polarizations due to its high-level symmetry. This configuration attains negative permittivity and permeability suitable for operational frequencies in the L-band and S-band. The study examines the electric field, impedance, and surface current to provide additional evidence for the absorption analysis. A validated RLC circuit equivalent to the proposed structure has been confirmed using Advanced Design System (ADS). The results indicate a slight deviation, especially at frequencies beyond the resonance frequencies. The structure underwent fabrication and testing in an anechoic chamber, revealing a strong correlation between the simulated and measured results. The suggested absorber holds promise for ISM applications, radar systems, sensing technologies, and energy harvesting systems.

Multi-environment robust polarization navigation sensor and the parameter adaptive prediction method

As a type of photosensitive sensor, the polarization navigation sensor is susceptible to variations in external optical information. Experiments have demonstrated that light intensity is one of the factors influencing solution parameters. Considering that traditional polarization navigation sensor cannot detect light intensity effectively, a polarization sensor with light intensity detection capability is designed. Additionally, a neural network-based adaptive parameter method is proposed. By utilizing a neural network for the real-time solution degree of linear polarization (DLOP) and combining the light intensity information with polarization information from the new sensor, the method finally realizes the prediction of external solution parameters, thus enabling the solution model to adapt to the environmental variations. Finally, the effectiveness of the adaptive prediction method is verified by experiments. The results of outdoor experiments show that the adaptive prediction method reduces the mean square error (MSE) of angle of polarization (AOP) by approximately 42.11%, 44.78%, and 52.83% compared to the convention solution method under sunny, cloudy, and overcast conditions.

Simplistic metasurface design approach for incident angle and polarization insensitive rcs reduction

This paper proposes the design of a metasurface for polarization and incident angle-insensitive RCS reduction applications. An ellipse-shaped unit cell is utilized as a polarization converter, which is then arranged to form a checkerboard surface. While a single layer checkerboard structure gives a wideband RCS reduction, a double layer structure yields polarization and incident angle independent operation. The two layers have unit cells rotated 450 to each other. Experimental results demonstrate an RCS reduction bandwidth of around 90%. Further the RCS reduction remains stable with polarization and incident angle variation.

Polarization-dependent near-field coupling and far-field harmonic modulation in a graphene-based plasmonic nanostructure

The interplay between light and matter has fostered innovative research in surface plasmons, specifically in graphene, due to its tunable Fermi energy and reduced losses in the infrared and terahertz spectra. This study explores the anisotropic coupling of nonlocalized surface plasmons in graphene with localized magnetic polaritons (MP) in a silicon carbide (SiC) array. By adjusting graphene’s Fermi energy and polarization angle, we successfully achieved hybrid coupling, giving rise to three clearly distinguishable hybridized states. Using the coupled oscillator model as a framework, we conducted an analysis of the intricate multimode coupling and accurately ascertained the weighting efficiencies of the individual modes comprising the hybrids. By integrating the design principles of space-time coding metasurfaces, we successfully broadened the scope of the application, extending its reach from the near-field to the far-field. These novel discoveries pave new paths for advancements in thermal emitters, photonic systems, energy conversion technologies, and the creation of cutting-edge plasmonic devices.

Accurate Inspection and Super-Resolution Reconstruction for Additive Manufactured Defects Based on Stokes Vector Method and Deep Learning

Defects in additive manufacturing processes are closely related to the mechanical and physical properties of the components. However, the extreme conditions of high temperatures, intense light, and powder during the manufacturing process present significant challenges for defect detection. Additionally, the high reflectivity of metallic components can cause pixels in image sensors to become overexposed, resulting in the loss of many defect signals. Thus, this paper mainly focuses on proposing an accurate inspection and super-resolution reconstruction method for additive manufactured defects based on Stokes vector and deep learning, where the Stokes vectors, polarization degree, and polarization angles of the inspected defects are effectively utilized to suppress the high reflectivity of metallic surfaces, enhance the contrast of defect regions, and highlight the boundaries of defects. Furthermore, a modified SRGAN model designated SRGAN-H is presented by employing an additional convolutional layer and activation functions, including Harswish and Tanh, to accelerate the convergence of the SRGAN-H network and improve the reconstruction of the additive manufactured defect region. The experiment results demonstrated that the SRGAN-H model outperformed SRGAN and traditional SR reconstruction algorithms in terms of the images of Stokes vectors, polarization degree, and polarization angles. For the scratch and hole test sets, the PSNR values were 33.405 and 31.159, respectively, and the SSIM values were 0.890 and 0.896, respectively. These results reflect the effectiveness of the SRGAN-H model in super-resolution reconstruction of scratch and hole images. For the scratch and hole images chosen in this study, the PSNR values of SRGAN-H for single image super-resolution reconstruction ranged from 31.86786 to 43.82374, higher than the results obtained by the pre-improvement SRGAN algorithm.

IXPE Observations of Magnetar Sources

Among the more than 60 sources observed in the first two years of operations, IXPE addressed four magnetars, neutron stars believed to host ultra-strong magnetic fields. We report here the main implication coming from IXPE measurements for the physics of magnetars. Polarimetric observations confirmed the expectations of high polarization degrees, up to ≈80%, values which have not been detected in any other source so far, providing further proof (independent from the P-P˙ estimate) that magnetars host indeed ultra-magnetized neutron stars. Polarization measurements also indicate that softer X-rays likely come from surface regions where the overlying atmosphere underwent magnetic condensation. The agreement of the phase-dependent polarization angle with a simple rotating vector model strongly supports the presence of vacuum birefringence around the star.

Research on sensing characteristics of high Q-factor all-dielectric metasurfaces based on geometric breaking

The bound states in the continuum (BIC) are widely used in designing metamaterials with high quality factor (Q-factor) resonances due to their perfect localization in the continuous spectral range coexisting with expanding waves. In this study, a T-shaped nanohole all-dielectric metasurface structure is proposed based on the unique electromagnetic properties of all-dielectric metasurfaces, and the fundamental reason of its coupled state and the theoretical basis of BIC excitation are deeply investigated based on the theory of group theory, and the geometric symmetry is broken from multiple angles, and the coupling relationship between discrete eigenmodes and the external continuum is specifically analyzed during the change of symmetry, its spectral response and near-field distribution are numerically calculated. In addition, based on the modulation mechanism of the incident light polarization angle, the three-channel resonance tuning with two resonances of the same frequency and one of a different frequency is realized under the condition that the resonance position and the Q-factor are not affected. This study not only provides a theoretical basis for the excitation conditions and evolution regularity of symmetry-protected BIC, but also solves the problem in the traditional analysis of resonance phenomena without taking the high Q-factor and stability into account, which can provide new designing methods for optical metasurface devices with multi-channel resonance.

Performance differences around polar angle vary systematically across experimental conditions

Performance differences around polar angle vary systematically across experimental conditions