Polarization Rotation Research Articles

Establishing the morphotropic phase boundary in van der Waals ferroelectrics

The formation of morphotropic phase boundaries (MPBs) is a pivotal strategy in piezoelectric ceramics and crystals, primarily used to enhance the electromechanical coupling. However, the application of this strategy in van der Waals (vdW) piezoelectrics and ferroelectrics has been limited, largely due to challenges in achieving phase coexistence and enabling possible polarization rotation. In this study, we address this gap by synthesizing a Selenium doped vdW ferroelectric, CuInP2(S1−x Se x )6, with a doping range of 0 ⩽ x⩽ 0.15, to create an MPB. Our findings indicate the presence of an MPB near x = 0.05, situated between monoclinic and trigonal phases. This boundary was confirmed using x-ray diffraction and transmission electron microscope techniques. Remarkably, the composition at x = 0.05 shows a high dielectric constant (ϵr = 13.8) and an impressive local effective piezoelectric coefficient (d 33eff = 51 pm V−1) at 80 K. Additionally, an unusual softening of the Young’s modulus was observed near MPB. These results are crucial for enhancing electromechanical coupling in vdW layered materials and herald new avenues for the design and optimization of piezoelectric and electromechanical properties in these materials.

Studies on the compositional dependent structural and electrical properties of CaTiO3-modified K0.5Na0.5NbO3 piezoelectric system

Lead-free piezoelectric ceramics of (1 − x)K0.5Na0.5NbO3-xCaTiO3 were fabricated, and their crystal structure, microstructure, and electrical properties were systematically studied. Rietveld refinement of the x-ray diffraction data and Raman spectroscopic analyses revealed a composition-dependent structural phase transition: three phase transitions, namely, from a pure orthorhombic phase for x ≤ 0.02 to a mixed phase of orthorhombic and tetragonal phases (0.03 ≤ x ≤ 0.08) and finally another mixed phase of tetragonal + cubic for x = 0.10 and 0.15 at room temperature (RT). The morphological study reveals a decrease in grain size along with a more uniform distribution of grains as the concentration of CaTiO3 (CT) increases; notably, a homogeneous distribution of grains is observed for x = 0.05. The temperature-dependent dielectric properties show two phase transitions, from orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), for unmodified K0.5Na0.5NbO3 (KNN). However, both the phase transition temperatures (TO-T and TC) decrease, and the transition peaks broaden with an increase in CT substitution, and for x > 0.06, the TO-T shifted below RT. The broadening of the transition peak at TO-T may be due to the relaxation behavior. Among the prepared samples, the 5 mol. % CT-modified KNN shows the optimum electrical properties (d33 = 114 pC/N, ɛr = 412, and 2Pr = 15.25 μC/cm2) at RT. The enhanced electrical properties for x = 0.05 are due to the coexistence of orthorhombic and tetragonal phases, facilitating easy polarization rotation and flattening of the free energy profile. A phase diagram has been constructed based on the information gathered from the temperature-dependent dielectric measurements, RT x-ray diffraction, and Raman spectroscopy data and is discussed in detail.

Mode-locking and wavelength-tuning of a NPR fiber laser based on optical speckle.

Passively mode-locked fiber lasers based on nonlinear polarization rotation (NPR) have been widely used due to their ability to produce short pulses with high peak power. Nevertheless, environmental perturbations can influence the mode-locked state, making it a challenge for the practical implementation. Therefore, researchers are searching for assessment criteria to quickly assist and maintain mode-locking of NPR fiber lasers. Speckle patterns containing spectral information can be generated when the laser transmits through a scattering medium, which can serve as indicators of the mode-locked state. The mode-locked regions are confined to the area close to the minimum texture contrast of speckle patterns. Based on these characteristics, we manually simulate the automatic mode-locking (AML). In addition, we utilize convolutional neural networks (CNNs) to recognize speckle patterns of wavelength tunable lasers and determine the center wavelength.

Enhanced Temperature Stability of Pyroelectric Sensing in Multilayer Potassium Sodium Niobate-Based Ceramics with Graded Polarization Rotation.

Pyroelectric effect which refers to electrical responses induced by time temperature-dependent fluctuations has received extensive attention, showing promising application prospects for infrared (IR) technology. Although enhanced pyroelectric performances are obtained in potassium sodium niobate-based ceramics at room temperature via multi-symmetries coexistence design, the poor pyroelectric temperature stability is still an urging desire that needs to be resolved. Herin, by constructing multilayer composite ceramics and adjusting the proportion of stacked layers, improved pyroelectric coefficient, and figures of merit (FOMs), as well as enhanced temperature stabilities can be achieved. With a remained high pyroelectric coefficient of 5.45×10-4C m-2°C-1 at room temperature, the pyroelectric parameters almost keep unchanged in the temperature range of 30-100°C, showing great properties advantages compared with previous reports. The excellent properties can be attributed to the graded polarization rotation states among each lamination induced by successive phase transitions. The novel strategy for achieving stable pyroelectric sensing can further promote the application in the IR sensors field.

Recent Progress in Light Polarization Control Schemes for Silicon Integrated Photonics

AbstractLight polarization control is a target in photonics, and this paper provides a comprehensive review of research from various groups on the silicon‐on‐insulator (SOI) platform. It draws comparisons between devices such as polarization splitters (PS), polarizers, and polarization splitters/rotators (PSR). These devices are fabricated using various technologies, including silicon nanowires, ridge waveguides, hybrid plasmonic waveguides, and subwavelength grating (SWG) waveguides. A detailed review of polarizers used as cleanup filters in splitters is initiated. Subsequently, various polarization splitters utilizing asymmetric directional couplers (ADCs), which typically exhibiting low extinction ratios (ERs), are delved. To enhance ERs, a detailed comparison of methods outlined in the literature is provided. One notable method includes integrating on‐chip polarizers at both ports to eliminate unwanted light fractions and achieve exceptionally high ERs. Furthermore, SWG‐based polarizers and splitters commonly face issues with Bragg reflections that can affect other photonic devices and lasers and ways to minimize unwanted polarization back reflections in SWG‐designed polarization control devices are examined. Finally, emerging applications in mid‐infrared (MIR) sensing are explored, highlighting the necessity of polarization rotators for on‐chip transverse electric (TE) operation, since quantum cascade lasers, the primary sources in this range, emitting radiation in the (TM) mode.

Polarization rotator with large bandwidth and low insert loss based on lemon core photonic crystal fiber

Polarization rotator with large bandwidth and low insert loss based on lemon core photonic crystal fiber

Optimized pyroelectric behaviors by constructing the nonergodic-ergodic transition state

Bi0.5Na0.5TiO3 (BNT)-based relaxors are considered as potential candidates for pyroelectric applications due to their excellent pyroelectric performances. However, the excellent pyroelectric response in BNT-based relaxors is generally accompanied by a rapid decrease in the depolarization temperature Td, limiting the operation temperature. Herein, we find that the mixed non-ergodic and ergodic relaxor states (a kind of transition system) can promote polarization rotation and remain the reversibility of polarization transformation simultaneously, thereby improving pyroelectric performances and maintaining the Td . The Li+-doped BNKT-based relaxors which possess such a transition state exhibit excellent room temperature (RT) pyroelectric coefficients (1247 μCm−2K−1), and also, the Td can maintain at 69℃. This work provides a strategy for further insight into the enhanced pyroelectric response, which promotes the development of eco-friendly pyroelectric applications (such as infrared detection, temperature sensors, and pyroelectric energy harvesting).

A new method for synthesis and designing transmissive linear-to-circular polarization converters based on branch line circuit model

This paper proposes a new design method of a linear-to-circular polarization converter based on the branch line circuit model. The series branches are implemented by dielectric spacers and the shunt branches are implemented by anisotropic admittance sheets. The admittance matrix of the anisotropic admittance sheets is derived by even and odd mode analysis. A unit cell consisting of two metal layers and a dielectric spacer is then designed using an iterative algorithm for operation from 15.5 to 23 GHz. Results indicate that the axial ratio and insertion loss of the designed polarizer are better than 3 and 1.5 dB respectively, for incident angles between ±45°. To validate the simulation results, a waveguide-based test setup is designed and fabricated, with measurement results indicating good agreement with simulations. The proposed method can be potentially applied to design other anisotropic structures such as half-plate polarizers and polarization rotators.

An Emergent Quadruple Phase Ensemble in Doped Bismuth Ferrite Thin Films Through Site and Strain Engineering

AbstractIn ferroic materials, giant susceptibilities can be realized at artificially constructed phase boundaries through deterministic manipulation of the order parameter. Here, emergent ferroelectric structural phase evolution behavior is demonstrated through a synergistic combination of A‐site doping and strain engineering. Using chemical solution deposition derived (001)‐oriented Sm‐substituted bismuth ferrite (Bi1‐xSmxFeO3) films as a prototypical system, a morphotropic phase boundary comprising a coexistence of four distinct crystallographic phases is uncovered. These ferroelectric, polar, and nonpolar phases form a nanoscale mixture without the presence of crystallographically hard boundaries. The system thus possesses the ability to show both polarization rotation and extension, effectively releasing the polarization from its crystallographic constraint. Consequently, both robust ferroelectric properties and giant electromechanical responses are obtained. For instance, the optimized composition with x = 0.14 has a remnant polarization of 2Pr = 103 µC cm−2 and electromechanical response 175% that of undoped BFO. These findings showcase the tremendous potential of synthetic phase boundaries, particularly in the context of lead‐free functional multiferroics.

Polarization rotation and exact transverse electromagnetic wave solutions in topological insulators

Polarization rotation and exact transverse electromagnetic wave solutions in topological insulators

Buildup of different emission regimes in a nonlinear polarization rotation modelocked all-fiber laser

We investigated experimentally and theoretically the buildup of light pulses in an erbium-doped sub-MHz all-fiber laser modelocked by nonlinear polarization rotation. We were able to study the buildup of two different emission regimes: standard solitons and noise-like pulses. In each case, we were able to determine the round-trips required to achieve a stable emission state. Temporal traces and optical spectra of single pulses were measured along the start-up transient of the laser. The experimental results were also confirmed by numerical simulations. Under the specific conditions of this laser, the soliton regime takes about 400 round-trips to reach single-pulse emission. In the noise-like pulse regime, it takes only 20 round-trips for the characteristics of noise-like pulses to show up; although a more steady-state emission is reached also at about 400 round-trips.

43‐3: Distinguished Paper: Breaking the Optical Efficiency Limit of Pancake Optics in Virtual Reality

We propose a theoretically lossless pancake optics solution that incorporates a nonreciprocal polarization rotator sandwiched between two reflective polarizers. A proof‐of‐concept experiment using a commercially available Faraday rotator (FR) is implemented. The theoretically predicted 100% efficiency can indeed be achieved approximately by using two high extinction ratio reflective polarizers.

Long-range fiber-based laser Doppler vibrometer using Faraday rotator for polarization-rotation compensation

In this paper, we report a method for extending distance of an optical fiber-based laser Doppler vibrometer system. This method uses a Faraday rotator (FR) to compensate polarization rotation in an installed long-range optical fiber. The construction of the proposed system is simple and achieved only by adding the FR to the sensing head unit, leading to stable and highly reliable vibration measurement even by using a long-range optical fiber exceeding kilometer. Experiments by using 100-m and 10-km long standard single mode fibers with emulated polarization rotation verified advantages of the proposed method; the system performances retained almost the same values even when the polarization state of reflected light was randomly rotated in installed optical fibers.

Nano-achiral complex composites for extreme polarization optics.

Composites from 2D nanomaterials show uniquely high electrical, thermal and mechanical properties1,2. Pairing their robustness with polarization rotation is needed for hyperspectral optics in extreme conditions3,4. However, the rigid nanoplatelets have randomized achiral shapes, which scramble the circular polarization of photons with comparable wavelengths. Here we show that multilayer nanocomposites from 2D nanomaterials with complex textured surfaces strongly and controllably rotate light polarization, despite being nano-achiral and partially disordered. The intense circular dichroism (CD) in nanocomposite films originates from the diagonal patterns of wrinkles, grooves or ridges, leading to an angular offset between axes of linear birefringence (LB) and linear dichroism (LD). Stratification of the layer-by-layer (LBL) assemblednanocomposites affords precise engineering of the polarization-active materials from imprecise nanoplatelets with an optical asymmetry g-factor of 1.0, exceeding those of typical nanomaterials by about 500 times. High thermal resilience of the composite optics enables operating temperature as high as 250 °C and imaging of hot emitters in the near-infrared (NIR) part of the spectrum. Combining LBL engineered nanocomposites with achiral dyes results in anisotropic factors for circularly polarized emission approaching the theoretical limit. The generality of the observed phenomena is demonstrated by nanocomposite polarizers from molybdenum sulfide (MoS2), MXene and graphene oxide (GO) and by two manufacturing methods. A large family of LBL optical nanocomponents can be computationally designed and additively engineered for ruggedized optics.

Multifunctional Meta-Devices for Full-Polarization Rotation and Focusing in the Near-Infrared.

The creation of multi-channel focused beams with arbitrary polarization states and their corresponding optical torques finds effective applications in the field of optical manipulation at the micro-nanoscale. The existing metasurface-based technologies for polarization rotation have made some progress, but they have been limited to single functions and have not yet achieved the generation of full polarization. In this work, we propose a multi-channel and spatial-multiplexing interference strategy for the generation of multi-channel focusing beams with arbitrary polarization rotation based on all-dielectric birefringent metasurfaces via simultaneously regulating the propagation phase and the geometric phase and independently controlling the wavefronts at different circular polarizations. For the proof of concept, we demonstrate highly efficient multi-channel polarization rotation meta-devices. The meta-devices demonstrate ultra-high polarization extinction ratios and high focusing efficiencies at each polarization channel. Our work provides a compact and versatile wavefront-shaping methodology for full-polarization control, paving a new path for planar multifunctional meta-optical devices in optical manipulation at micro-nano dimensions.

Remarkable flexibility in freestanding single-crystalline antiferroelectric PbZrO3 membranes

The ultrahigh flexibility and elasticity achieved in freestanding single-crystalline ferroelectric oxide membranes have attracted much attention recently. However, for antiferroelectric oxides, the flexibility limit and fundamental mechanism in their freestanding membranes are still not explored clearly. Here, we successfully fabricate freestanding single-crystalline PbZrO3 membranes by a water-soluble sacrificial layer technique. They exhibit good antiferroelectricity and have a commensurate/incommensurate modulated microstructure. Moreover, they also have good shape recoverability when bending with a small radius of curvature (about 2.4 μm for the thickness of 120 nm), corresponding to a bending strain of 2.5%. They could tolerate a maximum bending strain as large as 3.5%, far beyond their bulk counterpart. Our atomistic simulations reveal that this remarkable flexibility originates from the antiferroelectric-ferroelectric phase transition with the aid of polarization rotation. This study not only suggests the mechanism of antiferroelectric oxides to achieve high flexibility but also paves the way for potential applications in flexible electronics.

Multi-function digital THz-metasurfaces based on phase change materials

An effective and digitally tunable reflective multi-function metasurface in the THz band is proposed. The introduced planar structure consists of an array of a well-designed double-split SRR (DSSRR) utilizing phase-change materials (PCMs) in the gap regions, leading to the controllable function of the metasurface due to the tuning of the crystallization level of PCMs. According to Pancharatnam-Berry's principle, this effect creates different electromagnetic responses only by employing two types of unit cells (bit-0 and bit-1) based on the proper addressing of the PCMs in the structure. It is reported that by digitally changing the coding sequence of the metasurface, it is individually capable of performing different functions such as polarization rotation, beam steering, and RCS reduction. The computational results have been verified by appropriate analytical equivalent electric-circuit modeling and the theory of antenna-arrays. The studied planar-structure with its tunable and coding properties might be suggested for advanced applications in THz sensing, communications, and imaging systems.

A MeerKAT Polarization Survey of Southern Calibration Sources

We report on full-Stokes L-band observations of 98 MeerKAT calibration sources. Linear polarization is detected in 71 objects above a fractional level of 0.2%. We identify ten sources with strong fractional linear polarization and low Faraday rotation measure that could be suitable for wide-band absolute polarization calibration. We detect significant circular polarization from 24% of the sample down to a detection level of 0.07%. Circularly polarized emission is seen only for flat spectrum sources α > −0.5. We compare our polarized intensities and Faraday synthesis results to data from the NVSS at 1400 MHz and the ATCA SPASS survey at 2300 MHz. NVSS data exist for 54 of our sources and SPASS data for 20 sources. The percent polarization and rotation measures from both surveys agree well with our results. The residual instrumental linear polarization for these observations is measured at 0.16%, and the residual instrumental circular polarization is measured at 0.05%. These levels may reflect either instabilities in the relative bandpass between the two polarization channels with either time or antenna orientation, or atmospheric/ionospheric variations with pointing direction. Tracking of the hourly gain solutions on J0408-6545 after transfer of the primary gain solutions suggests a deterioration of the gain stability by a factor of several starting about 2 hr after sunrise. This suggests that observing during the nighttime could dramatically improve the precision of polarization calibration.

A Geometry-Compensated Sensitivity Study of Polarimetric Bistatic Scattering for Rough Surface Observation

The use of bistatic polarimetric SAR for rough surface observation has attracted increasing interest in recent years, with its acquisition of additional polarimetric information. In this paper, we investigate the sensitivity of polarimetric variables to soil moisture and surface roughness, with the intention of locating favorable bistatic geometries for soil moisture retrieval. However, in the bistatic setting, the expanded imaging geometry is convolved with the polarimetric scattering response along with the in-scene variations in the soil moisture and surface roughness. The probing polarization states continuously evolve with the bistatic geometry, incurring varying polarization orientation angles. In this investigation, we propose to first compensate the bistatic polarimetric observations for the geometry-induced polarization rotation. Simulations based on a two-scale rough surface scattering model are then used to evaluate the optimal imaging geometry for the best sensitivity to the soil moisture content. We show the different sensing geometries associated with a full list of common polarimetric variables, as we seek favorable bistatic geometries in non-specular directions. The influences of both surface roughness scales are evaluated, with the small-scale roughness parameter imposing the greatest limitation on our results.

Photonic Metamaterial‐Inspired Polarization Manipulating Devices on Etchless Thin Film Lithium Niobate Platform

AbstractPhotonic metamaterials interact with light at the micro–nano scale, enabling unprecedented optical manipulation capabilities, which play a key role in nonlinear optics, spin optics, negative index, and zero index materials. Recently, thin‐film lithium niobate on insulator (LNOI) has emerged as a promising platform for integrated photonics due to its unique material properties, including an excellent electro–optic effect, wide transparency window, and low waveguide losses. Metamaterial structures are promising for constructing novel integrated photonic circuit building blocks on LNOI as they can provide advantageous circuit functionality. In this work, as a proof of concept, high‐performance polarization manipulating devices including polarization splitter rotator (PSR), polarization rotator (PR), and polarizer are demonstrated using photonic metamaterials on the etchless LNOI platform by introducing a silicon nitride layer on the top of LNOI wafer as the loading material. In this way, full advantage of lithium niobate (LN) can be taken to achieve various high‐performance integrated photonic devices, while avoiding the etching of LN and simplifying the fabrication process greatly, which can bring bright prospects for achieving large‐scale lithium niobate integrated photonic circuits.