Birefringence Polarization Research Articles

Association of polarimetric signatures with coronary plaque composition in patients with acute and chronic coronary syndrome: an intravascular polarization-sensitive optical coherence tomography study

Abstract Background Intravascular polarimetry with polarization-sensitive (PS-) optical coherence tomography (OCT) measures polarization properties, birefringence and depolarization, in parallel with structural features available with conventional OCT (Figure 1). Birefringence is elevated in collagen and collagen-synthesizing smooth muscle cells, which imparts mechanical integrity to fibrous caps. Depolarization is elevated in the presence of macrophages and lipid/necrotic core. Purpose This study aimed to investigate polarimetric signatures of coronary lesions in patients with acute coronary syndrome (ACS) and chronic coronary syndrome (CCS). Furthermore, we aimed to investigate diagnostic value for birefringence and depolarization of ACS culprit lesions discriminating from CCS target lesions. Methods This was the first-in-human study of intracoronary PS-OCT in Japan, consisting of 17 patients with ACS (n = 5) or CCS (n = 12) who underwent intravascular PS-OCT. ACS culprit lesions (ACS-lesions) and CCS target lesions (CCS-lesions) were included in the analysis, resulting in a total of 862 cross-sections. In the cross-sectional images, lumen segmentation and guidewire artifact were automatically segmented. The median value of birefringence and depolarization were automatically analyzed using depolarization cut-off value (cross-sectional level). Birefringence and depolarization of ACS- and CCS-lesions were compared by using a generalized estimating equation model. Receiver operating characteristic (ROC) analysis was used to investigate diagnostic performance of polarimetric signatures for the identification of ACS-lesions. Results Compared to CCS-lesions, ACS-lesions featured higher lipid-burden index and maximum lipid arc (both p < 0.05). Compared to the CCS-lesions, ACS-lesions exhibited significantly lower birefringence (p < 0.05) and higher depolarization (p < 0.05) (Figure 2). In the ROC analysis for differentiating ACS-lesions from CCS-lesions, area under the curves (AUC) for birefringence and depolarization were 0.712 and 0.672, respectively. In the multivariable ROC analysis in diagnosing ACS lesions, combination of birefringence with depolarization improved the AUC to 0.755 (p ＝ 0.025). Conclusions Intravascular PS-OCT provides quantitative compositional assessment of coronary lesions. Decreased birefringence and pronounced depolarization within the ACS-lesions indicate increased collagenolytic activity and the presence of macrophage infiltration, respectively. These results suggest that polarization properties may serve as quantitative imaging markers for assessing natural history of coronary atherosclerosis.

Wavelength tuning of VCSELs via controlled strain.

Besides major advantages for telecommunication applications, vertical-cavity surface-emitting lasers (VCSELs) have attracted interest for their potential for neuro-inspired computing, frequency comb generation, or high-frequency spin oscillations. In the meantime, strain applied to the laser structure has been shown to have a significant impact on the laser emission properties such as the polarization dynamics or birefringence. In this work, we further explore the influence of strain on VCSELs and how this effect could be used to fine-tune the laser wavelength. Through a comprehensive investigation, we demonstrate a consistent wavelength shift up to 1 nm and report a sensitivity between 0.12 and 0.18 nm/millistrain. We also record birefringence values up to 292 GHz. Our results show that a controlled strain level could be considered for fine wavelength tuning and possibly alleviate the selection of VCSEL for precise wavelength requirements.

Mueller-Gabor holographic microscopy

Despite the emergence of various methods for Mueller matrix recovery, achieving complete volumetric Mueller matrix retrieval remains a challenge. An alternative approach that leverages in-line Gabor holography to comprehensively extract polarization information from volumetric samples is introduced in this context. The proposed polarization-sensitive in-line Gabor holographic setup enables the recovery of the complete Mueller matrix of three-dimensional (3D) samples after the numerical repropagation of the holographically rendered complex field to various sample planes. This proposal is validated using a calibrated birefringent polarization test target, a sample of Calcium Oxalate crystals, and a volumetric sample containing microplastics, providing the 3D measurement of polarimetric parameters such as diattenuation, polarizance, depolarization, and retardance. The results agree with those obtained through reference methods based on image-plane brightfield polarimetry. The in-line Gabor holographic system proposed is sensitive to the axial variations in polarimetric information within volumetric samples without any mechanical movement nor optical adjustments— an accomplishment that remains elusive to conventional image-plane reference methods and non-holographic/interferometric systems. These findings emphasize the versatility and potential of this alternative approach in recovering the intricate polarization characteristics of 3D specimens, offering the first in-line holographic Mueller imaging to the best of the authors' knowledge.

Angular-Spectral Characteristics of Acousto-Optic Tunable Filters Based on Mercurous Halide Crystals.

The angular and spectral properties crucial for the functionality of acousto-optic (AO) devices are determined by phase-matching geometries in AO interactions. In applications such as spectral imagers based on acousto-optic tunable filters (AOTFs), systematic throughput is constrained by the angle separating diffracted and transmitted light. This research introduces an analytical model that elucidates the angular-spectral properties of diffracted beams in mercurous halide crystals. These crystals possess a wide transmissive spectral range, from visible light to long-wave infrared light. The study computes and confirms correlations between the separation angle and parameters including incident angle, polarization, acoustic angle, and crystal birefringence. Experimental validation conducted on mercurous halide and tellurium dioxide crystals demonstrates that higher birefringence in crystals significantly amplifies the separation angle, augmenting the device's performance. The study contributes to the development of devices with large separation angles during the design phase, enhancing systematic throughput in spectral imaging applications.

Tunable and responsive photonic bio‐inspired materials and their applications

AbstractBio‐enabled and bio‐mimetic nanomaterials represent functional materials, which use bio‐derived materials and synthetic components to bring the better of two, natural and synthetic, worlds. Prospective broad applications are flexibility and mechanical strength of lightweight structures, adaptive photonic functions and chiroptical activity, ambient processing and sustainability, and potential scalability along with broad sensing/communication abilities. Here, we summarize recent results on relevant functional photonic materials with responsive behavior under mechanical stresses, magnetic field, and changing chemical environment. We focus on recent achievements and trends in tuning optical materials' properties such as light scattering, absorption and reflection, light emission, structural colors, optical birefringence, linear and circular polarization for prospective applications in biosensing, optical communication, optical encoding, fast actuation, biomedical fields, and tunable optical appearance.

Polarization measuring astronomical instrument: an improved method

"This work deals with a new theoretical method proposed with the intent of improving the quality of astronomical polarimetric data. The theoretical method is ap- plied to one of the simplest possible birefringent type polarizer device constructs, being a hybrid measurement procedure between the fixed position angles and the continu- ous rotation records of the modulator (in our case, the quarter-wave plate) methods. It can be suitable for some astronomical applications in Planetary Science and Stellar As- trophysics, as their polarimetric parameters (polarization degree, polarization angle and Stokes parameters) have relatively stable values, allowing for the iterative proposed pro- cedure. The validity of the procedure is expected to be practically proven by comparing the quality of the polarization parameters obtained with it, on the proposed instrument, with the results obtained with a similar standardized instrument on the market."

Twist Phase Matching in Two-Dimensional Materials.

Optical phase matching involves establishing a proper phase relationship between the fundamental excitation and generated waves to enable efficient optical parametric processes. It is typically achieved through birefringence or periodic polarization. Here, we report that the interlayer twist angle in two-dimensional (2D) materials creates a nonlinear geometric phase that can compensate for the phase mismatch, and the vertical assembly of the 2D layers with a proper twist sequence generates a nontrivial "twist-phase-matching" (twist-PM) regime. The twist-PM model provides superior flexibility in the design of optical crystals, which can be applied for twisted layers with either periodic or random thickness distributions. The designed crystal from the twisted rhombohedral boron nitride films within a thickness of only 3.2 μm is capable of producing a second-harmonic generation with conversion efficiency of ∼8% and facile polarization controllability that is absent in conventional crystals. Our methodology establishes a platform for the rational design and atomic manufacturing of nonlinear optical crystals based on abundant 2D materials.

Tunable birefringence and elliptical polarization eigenmodes in a biplate of two quarter-wave plates.

Birefringence of elliptical polarization eigenmodes can be conceptualized as a composite system comprising two distinct media: one with linear polarization eigenmodes and the other with circular polarization eigenmodes. However, the practical realization of such a system often involves the combination of two birefringent quarter-wave plates (QWPs). In this study, our objective is to characterize the variable retardation and variable elliptical polarization eigenmodes exhibited by a biplate consisting of two quarter-wave plates. Additionally, we aim to analyze the geometric properties of the transformation of one state of polarization on the Poincaré sphere, employing the emerging state's curve. This curve corresponds to the intersection between the Poincaré sphere and a cone. The outcomes of our study are presented as a function of the angle between the fast axes of the two QWPs. The findings have the potential to contribute to the configuration of q-plates and facilitate the development of quantum communication protocols.

Sandwiched hybrid waveguide platform for integrated photonics application

We propose and demonstrate a hybrid waveguide platform using layered amorphous silicon and silicon nitride. The waveguide offers more degrees of freedom to design waveguides with desired confinement, effective index and polarization birefringence. Unlike single core material, the proposed waveguide offers design flexibility, and light confinement in the layers is polarization-dependent. We present a detailed waveguide design and analysis of efficient fiber-chip grating couplers with a coupling efficiency of −3.27 dB and −8 dB for TE and TM polarization, respectively. The couplers offer a 3 dB bandwidth of 100 nm. Furthermore, we demonstrate excitation of TE and TM modes exploiting the polarization-dependent confinement using thermo-optic characteristics of a ring resonator.

Field Extended Birefringent Static Doppler Wind Imaging Interferometer

According to the requirements for wide field of view and high resolution in wind imaging detection, the principle of a novel field extended birefringent wind imaging interferometer is proposed. Based on the principle of birefringent polarization wind imaging interferometer, the new optical system scheme of the field extended birefringent static Doppler wind imaging interferometer is designed, which overcomes the limitation of the field of view in the original birefringent polarization wind imaging interferometer. Compared with the original scheme, the new scheme eliminates the cross-field phase change between the top and bottom fields, and the available field of view of the instrument is no longer limited. The Jones matrix model are used to simulate to prove the correctness of the principal scheme of the field extended birefringent wind imaging interferometer.

Probing Lorentz-violating electrodynamics with CMB polarization

We perform a comprehensive study of the signatures of Lorentz violation in electrodynamics on the Cosmic Microwave Background (CMB) anisotropies. In the framework of the minimal Standard Model Extension (SME), we consider effects generated by renormalizable operators, both CPT-odd and CPT-even. These operators are responsible for sourcing, respectively, cosmic birefringence and circular polarization. We propagate jointly the effects of all the relevant Lorentz-violating parameters to CMB observables and provide constraints with the most recent CMB datasets. We bound the CPT-even coefficient to kF,E+B < 2.31 × 10-31 at 95% CL. This improves previous CMB bounds by one order of magnitude. The limits we obtain on the CPT-odd coefficients, i.e. |k (3) (V)00| < 1.54 × 10-44 GeV and |kAF | < 0.74 × 10-44 GeV at 95% CL, are respectively one and two orders of magnitude stronger than previous CMB-based limits, superseding also bounds from non-CMB searches. This analysis provides the strongest constraints to date on CPT-violating coefficients in the minimal SME from CMB searches.

Phase portrait, bifurcation, chaotic pattern and optical soliton solutions of the Fokas-Lenells equation with cubic-quartic dispersion in optical fibers

The main purpose of this paper is to study the Fokas-Lenells equation with cubic-quartic dispersion describing the propagation of birefringent fibers and polarization preserving fibers. Firstly, using traveling wave transformation and homogeneous balance principle, the Fokas-Lenells equation with cubic-quartic dispersion is simplified into ordinary differential equation. Secondly, the dynamic properties of two-dimensional system and its perturbed system are studied. Finally, by using the trial method of polynomial of rank homogeneous equation, the optical soliton solutions of the Fokas-Lenells equation with cubic-quartic dispersion can be obtained. Moreover, three-dimensional diagram, two-dimensional diagram, density plot and contour plot of the obtained solutions are drawn by explaining the propagation of optical solitons.

Cosmic birefringence tomography and calibration independence with reionization signals in the CMB

ABSTRACTThe search for cosmic polarization rotation or birefringence in the cosmic microwave background (CMB) is well motivated because it can provide powerful constraints on parity-violating new physics, such as axion-like particles. In this paper, we point out that since the CMB polarization is produced at two very different redshifts – it is generated at both reionization and recombination – new parity-violating physics can generically rotate the polarization signals from these different sources by different amounts. We explore two implications of this. First, measurements of CMB birefringence are challenging because the effect is degenerate with a miscalibration of CMB polarization angles; however, by taking the difference of the reionization and recombination birefringence angles (measured from different CMB angular scales), we can obtain a cosmological signal that is immune to instrumental angle miscalibration. Secondly, we note that the combination with other methods for probing birefringence can give tomographic information, constraining the redshift origin of any physics producing birefringence. We forecast that the difference of the reionization and recombination birefringence angles can be competitively determined to within ∼0.05 deg for future CMB satellites such as LiteBIRD. Although much further work is needed, we argue that foreground mitigation for this measurement should be less challenging than for inflationary B-mode searches on similar scales due to larger signals and lower foregrounds.

Autocorrelation functions and power spectral densities of the Stokes parameters in a polarization speckle pattern.

The concept of ensemble-average polarization and coherence has been applied to studying fluctuating Stokes parameters in a polarization speckle observed when coherent light is passed through a birefringent polarization scrambler. With the aid of the ensemble-average van Cittert-Zernike theorem for the propagation of ensemble-average polar-coherence, we invesitgate the autocorrelation functions and power spectra of the Stokes parameters to expose the dependence of the polarization-related scale-size distributions on the optical geometries in which the polarization speckle arises. A generalized concept of the Stokes ensemble-average coherence areas is introduced to deal with the polarization-related average areas associated with polarization speckle.

A Fiber-Optic Extrinsic Fabry–Perot Hydrophone Based on Archimedes Spiral-Type Sensitive Diaphragm

A fiber-optic hydrophone based on extrinsic Fabry–Perot (F-P) interferometer is proposed. The sensitive element of the hydrophone is an Archimedes spiral metal diaphragm, and the inner surface of the diaphragm and the end face of the optical fiber form the F-P cavity. Due to the grooved surface of the sensitive diaphragm, the hydrophone is minimally affected by hydrostatic pressure. The geometry structure of sensor and finite element method (FEM) modeling is presented. Experiments of underwater acoustic response and sensitivity calibration of the hydrophone are carried out and the experimental phase results are demodulated by the orthogonal phase demodulation method based on birefringent crystals and polarization technology. The experiment results show that the hydrophone has a relatively flat signal-to-noise ratio (SNR) and sensitivity within 1–20 kHz, and the average sensitivity is −172.52 dB (re. 1 rad/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Pa) @ 1–20 kHz. We believe that this type of hydrophone has the potential to be applied in the field of underwater acoustic communication.

Highly birefringent polarization maintaining low-loss single-mode hollow-core antiresonant fiber

In this paper, a highly birefringent polarization maintaining low losses and a single mode antiresonant hollow core fiber is proposed and analyzed, that is able to exhibit better performances compared to the recent related structures. The usage of bi-thickness cladding tubes with additional high refractive index layers on our geometrically optimized structure improves birefringence nearly by one order: the highest birefringence is 4.7 × 10−4 at 1.51 µm and sustains &gt; 1 × 10−4 for a wide bandwidth of 100 nm with a larger core diameter of 26 µm. Elliptical nesting on our proposed structure lowers the confinement loss to 0.007 dB/m at 1.51 µm and maintains a loss of &lt; 1 dB/m for a wide range of 210 nm. A polarization extinction ratio of 300 and higher order mode extinction ratio of 63, for our fiber, ensure a single polarization and single mode operation at 1.51 µm. Moreover, the proposed fiber exhibits a bend robust performance with a very low bend loss of 0.009 dB/m at a small bend radius of 6 cm and sustains a bend loss of &lt; 0.01 dB/m from a bend radius of 4 cm and above. Hence, our presented fiber, containing the above excellent characteristics, may be fruitful for designing polarization-controlled devices (fiber optic sensors, fiber optic amplifiers, fiber optic gyroscope, etc.) in the field of optical communication.

Planck constraints on cross-correlations between anisotropic cosmic birefringence and CMB polarization

Cosmic Birefringence (CB) is the in-vacuo rotation of the linear polarization direction of photons during propagation, caused by parity-violating extensions of Maxwell electromagnetism. We build low resolution CB angle maps using Planck Legacy and NPIPE products and provide for the first time estimates of the cross-correlation spectra CL αE and CL αB between the CB and the CMB polarization fields. We also provide updated CB auto-correlation spectra CL αα as well as the cross-correlation CL αT with the CMB temperature field. We report constraints by defining the scale-invariant amplitudes AαX ≡ L(L + 1)CL αX /2π, where X = α, T, E, B, finding no evidence of CB. In particular, we find AαE = (-7.8 ± 5.6) nK deg and AαB = (0.3 ± 4.0) nK deg at 68% C.L..

Research on novel single-mode polarization maintaining photonic crystal fiber

Abstract A PCF (photonic crystal fiber) with high birefringence and single-mode polarization retention over a wide wavelength range is designed and studied. The birefringence and polarization retention characteristics of the PCF base mode were studied using FVFEM (full vector finite element method) and APML (anisotropic perfect matching layer) as boundary conditions. The simulation results show that by rotating the elliptical air hole parallel to the horizontal axis by 45°, and then rotating the elliptical air hole parallel to the longitudinal axis by 45°, the birefringence of the PCF obtained is as high as 4.7 × 10−2, and it has good single model ability, which can be used for various optical devices.

Space-variant polarization conversion with artificial birefringent metallic elements

We present an artificial birefringent space-variant polarization converter for the near infrared, λ = 1550 nm. Each hollow waveguide has a rectangular shape with lateral dimensions of 1550 nm in the x-direction and 1034 nm as the largest length in the y-direction. The whole device consists of approximately 2000 × 2500 hollow waveguides realized in a 2-µm-thick gold structure. They are separated by sidewalls with a width of less than 500 nm. By proper choice of the lateral widths of the individual holes, a pixel-wise polarization conversion of an incoming wave field is possible. By suitable choice of the fabrication parameters, a birefringent phase shift up to 2π can be achieved. Hence, the structure is able to fully convert the state of polarization, e.g., from linear to circular. For fabrication of the device, femtosecond 3D direct laser writing was combined with electroplating. Here, we describe the operation of our device as a space-variant polarization converter by measuring the angle-dependent transmitted power and by calculating the ellipticity and the phase delay dependent on position as well as the azimuth angle from the experimentally determined powers.

Multicontrast investigation of in vivo wildtype zebrafish in three development stages using polarization-sensitive optical coherence tomography.

.Significance: The scattering and polarization characteristics of various organs of in vivo wildtype zebrafish in three development stages were investigated using a non-destructive and label-free approach. The presented results showed a promising first step for the usability of Jones-matrix optical coherence tomography (JM-OCT) in zebrafish-based research.Aim: We aim to visualize and quantify the scatter and polarization signatures of various zebrafish organs for larvae, juvenile, and young adult animals in vivo in a non-invasive and label-free way.Approach: A custom-built polarization-sensitive JM-OCT setup in combination with a motorized translation stage was utilized to investigate live zebrafish. Depth-resolved scattering (intensity and attenuation coefficient) and polarization (birefringence and degree of polarization uniformity) properties were analyzed. OCT angiography (OCT-A) was utilized to investigate the vasculature label-free and non-destructively.Results: The scatter and polarization signatures of the zebrafish organs such as the eye, gills, and muscles were investigated. The attenuation coefficient and birefringence changes between 1- and 2-month-old animals were evaluated in selected organs. OCT-A revealed the vasculature of in vivo larvae and juvenile zebrafish in a label-free manner.Conclusions: JM-OCT offers a rapid, label-free, non-invasive, tissue specific, and three-dimensional imaging tool to investigate in vivo processes in zebrafish in various development stages.