Change In Polarization Of Light Research Articles

Ontogeny and Early Steps of the Calcification Process in Coralline Algae Lithophyllum corallinae (Florideophyceae, Rhodophyta)

Coralline algae (Rhodophyta, Florideophyceae) are one of the most abundant organisms in the hard-bottom marine photic zone where they provide settlement substrates, structure and shelter on rocky substrates. Coralline algae also play important roles in tropical reefs, both cementing corals together and producing substantial amounts of calcium carbonate. The ecological roles of coralline algae in the marine environment are related to the biomineralization process that occurs in the cell walls. Currently, this group of algae is receiving renewed attention from researchers from different fields, especially due to possible effects of climate changes over its magnesium calcite skeleton. Despite this renewed attention, we still have poor information regarding the first steps of coralline algae ontogeny and calcification. The aim of this study was to describe the earlier steps ofLithophyllum corallinaedevelopment and its calcification process. Algae were collected at Vermelha Beach, Rio de Janeiro city. Adult crusts released spores that settled over microscope slides. The germinating spores were analyzed by Polarizing Light Microscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Transmission Electron Microscopy and Atomic Force Microscopy. Results showed that cell walls mineralization begins at third spore cell division (8 cells specimen), evidenced by changes in light polarization, elemental composition and hardness, restricted to the cell walls of the innermost part of the developing spore. Nanopores in calcite crystals structure were identified, evidencing macromolecules occlusion, a feature especially important to prevent calcite skeleton cracking in high-energy environments. The beginning of this process could be related to spore size, availability of organic matrix and energy from photosynthesis. All the analysis also confirmed the lack of calcification in the cell walls of the outermost part of the germinating spore, which allows the growth of the individual; but mainly indicates a high level of control in coralline algae mineralization process, representing a relevant information in future studies on coralline algae calcification, including those testing climate changes scenarios.

All fiber temperature sensor based on light polarization measurement utilizing graphene coated tapered fiber

AbstractIn this work, all fiber temperature measurement based on change of light polarization is demonstrated using tapered fiber coated with graphene. The large evanescent field of tapered fiber allows graphene to absorb the surrounding heat and subsequently this changes the refractive index of graphene coated tapered fiber. The change of refractive index is due to thermo‐optic effect. When there is a change in surrounding temperature, refractive index of the coated tapered fiber changes and this subsequently modifies the injected light polarization. The proposed temperature sensor can measure temperature up to 250°C and its sensitivity is ascertained at 0.48°/°C. The proposed temperature sensor is beneficial for future Internet of Things (IoT) applications.

Quantum theory of polarimetry: From quantum operations to Mueller matrices

Quantum descriptions of polarization show the rich degrees of freedom underlying classical light. While changes in polarization of light are well-described classically, a full quantum description of polarimetry, which characterizes substances by their effects on incident light's polarization, is lacking. We provide sets of quantum channels that underlie classical polarimetry and thus correspond to arbitrary Mueller matrices. This allows us to inspect how the quantum properties of light change in a classical polarimetry experiment, and to investigate the extra flexibility that quantum states have during such transformations. Moreover, our quantum channels imply a new method for discriminating between depolarizing and nondepolarizing Mueller matrices, which has been the subject of much research. This theory can now be taken advantage of to improve estimation strategies in classical polarimetry and to further explore the boundaries between classical and quantum polarization.

Effect of ozone addition on virgin coconut oil using changes in light transmission polarization

Today, the investigation of ozonized cooking oil becomes a very interesting research development topic, in addition to the study of ozone interactions in liquids and its application to the treatment of skin cancer. This research was conducted to determine the change in the transmission polarization angle in Virgin Coconut Oil (VCO) that was interacted with ozone. Laser pointers with a wavelength of 650 nm were used as light sources. The polarization changes are proportional to the duration of ozonation, and the longer duration is accompanied by more accumulative numbers of free fatty acids. The interaction is considered to be quite effective, with supposedly one ozone molecule interacting with one symmetric triglyceride molecule to become a new asymmetric triglyceride molecule in the interaction. This interaction increases the active optical properties of VCO samples. In contrast to the latest sophisticated spectroscopic methods, the polarization method seems simpler by simply measuring the change in polarization of light. With the ability of the polarization method that can distinguish the characteristics of cooking oil before and after experiencing treatment, this method has a large chance to be developed in subsequent studies relating to polarization as an indicator of the interaction of light with the material in the field of biophysics and other related fields.

Origin of chiroptical activity in nanorod assemblies.

Spectroscopy disentangles changes in light polarization from nanoparticles and proteins

Phase-shifted polarimetric surface plasmon resonance sensor using a liquid crystal retarder and a diverging beam.

A simple phase-shifted polarimetric scheme to extract light polarization changes induced by the sample in surface plasmon resonance (SPR) sensors is presented. The proposed method is based on the conventional Kretschmann-Raether configuration in the angular diverging beam mode using a single wavelength and a variable liquid crystal retarder. An experimental demonstration was performed using different aqueous solutions of ethylene glycol showing a sensitivity of 118.7deg/refractive-index-unit (RIU) and a detection limit of 1.03×10-7 RIU.

Twisted tilted fiber Bragg gratings: new structures and polarization properties.

In this Letter, it has been shown that the twisting of TFBGs (tilted fiber Bragg gratings) decreases their sensitivity to the polarization of the input light. It has been proved by a theoretical simulation study that twisting the TFBG by 180° eliminates the sensitivity of the grating to input light polarization changes. We have experimentally proved that our structure produced has an 18 times lower coefficient of variation of transmission for polarization changes than the untwisted TFBG. This Letter also presents a new method for manufacturing the twisted tilted fiber Bragg grating (TTFBG). We have demonstrated the possibility of writing the TTFBG structure twisted by 90° on a fiber with a length of 10mm. The structure has been further twisted in the other direction by 90°, which is consistent with a structure twisted by 180°. The properties of both structures were determined. Due to the fiber's strength, the TTFBG twisted by 180° has to be 2cm long. An advantage of the proposed method of producing the TTFBG is that there is a twist of the structure itself after fabrication. This creates new possibilities of using the structure in many applications. This type of grating can be used to reduce the sensitivity to polarization in various sensing applications, in particular, to measure the refractive index. In addition, a 180° twisted TTFBG has properties of direction discrimination in twist sensing applications.

Analysis of polarized-light effects in glass-promoting solutions with applications to cryopreservation and organ banking.

This study presents experimental results and an analysis approach for polarized light effects associated with thermomechanical stress during cooling of glass promoting solutions, with applications to cryopreservation and tissue banking in a process known as vitrification. Polarized light means have been previously integrated into the cryomacroscope—a visualization device to detect physical effects associated with cryopreservation success, such as crystallization, fracture formation, and contamination. The experimental study concerns vitrification in a cuvette, which is a rectangular container. Polarized light modeling in the cuvette is based on subdividing the tridimensional (3D) domain into a series of planar (2D) problems, for which a mathematical solution is available in the literature. The current analysis is based on tracking the accumulated changes in light polarization and magnitude, as it passes through the sequence of planar problems. Results of this study show qualitative agreement in light intensity history and distribution between experimental data and simulated results. The simulated results help explaining differences between 2D and 3D effects in photoelasticity, most notably, the counterintuitive observation that high stress areas may correlate with low light intensity regions based on the particular experimental conditions. Finally, it is suggested that polarized-light analysis must always be accompanied by thermomechanical stress modeling in order to explain 3D effects.

Measurement of Surfactant Concentration Using Light Scattering Method

A method for measuring the concentration of surfactant in water was developed. In this technique, microbubbles were used as light scatterers. The polarization change of light scattered by microbubbles was analyzed by Mueller matrix analysis. M₁₁, one of the Mueller matrix elements, was found to be a key parameter inferring the surfactant concentration within the concentration range of 0 ppm to 60 ppm. The best results for this measurement were obtained when the scattering angle was 150° and the extinction ratio was 56.2. This experimental result shows that the EPLS can be effectively used as a real time inspection method for water quality monitoring in lakes or rivers. Key words: Light Scattering, Micro-Bubble, Polarization, Mueller Matrix, Surfactant Concentration

Compact mirror-tunable laser interference system for wafer-scale patterning of grating structures with flexible periodicity

This paper presents a novel mirror-tunable laser interference system for the wafer-scale patterning (>4-in.) of submicron grating structures with a flexible periodicity (200–1000 nm) in a compact and cost-effective manner. The proposed system guides and splits the laser beam into two expanded light beams propagating in a downward direction to be reflected by rotatable ultraviolet mirrors to produce interference patterns. The incident angle of two light beams can be controlled by rotating the mirrors until they match the targeted periodicity of the grating, without the need to reconfigure the optical paths. The fact that light polarization changes with the rotation angle of the mirrors necessitates the use of a half-wave plate along each optical path to adjust the direction of polarization perpendicular to the plane of incident light. The proposed system enables large-area fabrication and wide-range grating tunability, making it highly useful for applications that require wafer-scale patterning of submicron periodic structures, such as flexible wire-grid polarizers for displays, patterned sapphire substrates for light-emitting diodes, and Bragg gratings for distributed feedback lasers.

Anisotropic optical response of GaN and AlN nanowires

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp3, that includes the spin–orbit interaction. The passivation of the dangling bonds at the free surfaces is also studied, together with the effects on the electronic structure of the nanowire. For both GaN and AlN nanowires, we have found a remarkable anisotropy of the optical absorption when the light-polarization changes, showing in the case of GaN a dependence on the nanowire size.

Contrast improvement in scattered light confocal imaging of skin birefringent structures by depolarization detection

Here we describe a method for enhancing the contrast in imaging skin birefringent structures. The method relies on polarization-dependent optical properties and is implemented using cross polarized confocal microscopy. The experimental data obtained using ex-vivo and in-vivo measurements on human scalp hairs and human skin demonstrate a significant dependence of the change in polarization of light that interacted with the birefringent hair on the orientation of the incident polarization. The polarization dependent contrast, defined as the ratio of intensity measured for different orientations of the incident polarization when observed using cross polarized confocal microscopy furthermore depends on the hair type/degree of pigmentation and on the focusing depth inside the hair. No such dependence was observed for the upper skin layers, including the stratum corneum and epidermis. We propose a new method for enhancing the contrast between the skin and the birefringent hair by the use of cross polarized confocal microscopy combined with the variation of the polarization of the incoming light. Potential applications of this method include imaging of hairs for assessing the efficacy of hair removal methods and measurement of skin birefringence. The underestimation of the birefringence content resulting from the orientation related effects associated with the use of linearly polarized light for imaging tissues containing wavy birefringent structures could be minimized by this method.

Effect of light polarization on holographic recording in glassy azocompounds and chalcogenides

Abstract Light polarization effects on a holographic grating recording in a glassy chalcogenide a-As40S15Se45 film has been experimentally studied and compared with previously studied glassy molecular azobenzene film 8a at 633, using s − s,p − p, CE-1 and CE-2 circular-elliptic recording-beam polarizations (differing by light electric field rotation directions). The azocompound exhibited much higher self-diffraction efficiency (SDE) and diffraction efficiency whereas chalcogenide was more sensitive. Their recording efficiency polarization dependences also were different. SDE up to 45% was achieved in 8a with p − p and up to 2.6% in a-As40S15Se45 with CE-2 polarized recording beams. The polarization changes in the diffraction process were studied as well in these and other materials (11, 16, 19 and a-As2S3 film, LiTaO3:Fe crystal). It was found that light polarization changes in the process of diffraction from gratings recorded vectorially by s−p polarizations depended on chemical composition, wavelength, and exposure time. Vector gratings with SDE up to 25% were recorded in 8a, rotating a linear polarization by 90°. No light polarization changes were found in azobenzene 19 and chalcogenide films and in LiTaO3:Fe crystal, thus showing a vector recording of scalar holograms. The recording mechanisms in azocompounds and chalcogenides are discussed and compared.

Test of fiber optic based current sensors on the Tore Supra tokamak

Fiber optic current sensors have been recently considered for current measurements in ITER. These sensors exploit Ampere's law by measuring the change of light polarization along an optical fiber subjected to a magnetic field aligned along the fiber axis. Through collaboration between CEA and SCK·CEN, such fiber optic current sensors have been installed on Tore Supra tokamak as a first demonstration for possible future applications in ITER. This paper aims at reporting the results obtained on Tore Supra. It discusses the technique used to separate the effects of the intrinsic linear birefringence and the magneto-induced circular birefringence, the latter enabling the determination of the current flowing through the area defined by the optic fiber loop. Three optical fibers have been installed on Tore Supra for assessment of their linearity response on a wide range of plasma current from 0.3 to 1.4 MA as well as their long term stability. The extrapolation of the results and the issues related to a future application on ITER are finally discussed.

Differential optical spectropolarimetric imaging system assisted by liquid crystal devices for skin imaging

Skin cancer diagnosis depends not only on histopathological examination but also on visual inspection before and after the excision of suspected lesion. Neoplasm is accompanied with changes in birefringence of collagen, pleomorphicity, and hyperchromatic state of epithelial nuclei. These phenomena can be measured by spectral and polarization changes of light backscattered by the examined tissue. A new differential spectropolarimetric system is proposed using liquid crystal devices, one as a tunable filter and the other as a polarization rotator, both operating at wide spectral ranges from the visible to the near-infrared. Since collagen's fibrils texture orientation depends on its location in the skin and since it is not well organized, our system scans the bipolarization states by continuously rotating the linearly polarized light incident on a skin lesion, and collecting differential contrasts between sequenced images when simultaneously averaging the statistical readout of a video camera. This noninvasive method emphasizes areas on skin where the neoplasm, or tumor, minimizes the statistical polarization change of the scattered light from the lesion. The module can be considered as an assistant tool for epiluminescence microscopy. Images of skin tumors were captured in vivo before the patients having their surgery and compared to histopathological results.

Polarization dependence of holographic recording in glassy azocompounds

Polarization dependence of holographic grating recording in glassy molecular azobenzene films 8a, 11, and 16 has been experimentally studied at 633 and 532 nm with s–s, p–p, CE-1 and CE-2 circular–elliptic (differing by light electric field rotation directions) recording beam polarizations. Samples 8a and 11 with the simplest chemical structure were the most efficient at 633 nm, and sample 8a was the most efficient at 532 nm. Self-diffraction efficiency (SDE) up to 45% was achieved in 8a with p–p polarized recording beams at 633 nm. Linear p–p polarizations were the most efficient at 633 nm whereas CE-1 polarizations were the best at 532 nm. It was found that the light polarization changes in the process of diffraction depend on chemical composition, wavelength, and exposure time. Vector gratings with SDE up to 25% were recorded in 8a rotating a linear polarization by 900. Mainly erasure of gratings took place with one beam. Coherent self-enhancement of gratings was observed only for s–p and both CE polarizations in 8a at 532 nm and for s–p polarizations at 633 nm. Atomic force microscopy measurements also were made. The evidence is found for trans–cis photoisomerization holographic recording mechanism at both 532 and 633 nm. Studied films can be applied for production of polarization holographic optical elements and for permanent optical information recording. Keywords: molecular glassy azobenzene films, holographic gratings, light polarization, diffraction anisotropy

Light switching at low light level based on changes in light polarization

We studied the polarization spectroscopy of a linearly-polarized optical (probe) field in a multi-Zeeman-sublevel atomic system of the 87Rb D1 line. The polarization spectroscopy signals of the probe light result from the changes in its polarization, which are caused by a left-circularly polarized pumping beam. A theoretical analysis involving multiple Zeeman sublevels is presented and the results are in qualitative agreement with the experimental observations. Based on this phenomenon, we demonstrated a light switch at low light level (∼68 photons per λ2/2π) with a switching efficiency of ∼3%.

Action potential propagation imaged with high temporal resolution near-infrared video microscopy and polarized light

To identify the neural constituents responsible for generating polarized light changes, we created spatially resolved movies of propagating action potentials from stimulated lobster leg nerves using both reflection and transmission imaging modalities. Changes in light polarization are associated with membrane depolarization and provide sub-millisecond temporal resolution. Typically, signals are detected using light transmitted through tissue; however, because we eventually would like to apply polarization techniques in-vivo, reflected light is required. In transmission mode, the optical signal was largest throughout the center of the nerve, suggesting that most of the optical signal arose from the inner nerve bundle. In reflection mode, polarization changes were largest near the edges, suggesting that most of the optical signal arose from the outer sheath. In support of these observations, an optical model of the tissue showed that the outer sheath is more reflective while the inner nerve bundle is more transmissive. In order to apply these techniques in-vivo, we must consider that brain tissue does not have a regular orientation of processes as in the lobster nerve. We tested the effect of randomizing cell orientation by tying the nerve in an overhand knot prior to imaging, producing polarization changes that can be imaged even without regular cell orientations.

Impact of spin-zero particle-photon interactions on light polarization in external magnetic fields

If the recent PVLAS results on polarization changes of a linearly polarized laser beam passing through a magnetic field are interpreted by an axion-like particle, it is almost certain that it is not a standard QCD axion. Considering this, we study the general effective interactions of photons with spin-zero particles without restricting the latter to be a pseudo-scalar or a scalar, i.e., a parity eigenstate. At the lowest order in effective field theory, there are two dimension-5 interactions, each of which has previously been treated separately for a pseudo-scalar or a scalar particle. By following the evolution in an external magnetic field of the system of spin-zero particles and photons, we compute the changes in light polarization and the transition probability for two experimental set-ups: one-way propagation and round-trip propagation. While the first may be relevant for astrophysical sources of spin-zero particles, the second applies to laboratory optical experiments like PVLAS. In the one-way propagation, interesting phenomena can occur for special configurations of polarization where, for instance, transition occurs but light polarization does not change. For the round-trip propagation, however, the standard results of polarization changes for a pseudoscalar or a scalar are only modified by a factor that depends on the relative strength of the two interactions.

Electromagnetic Gyration: -- Hamiltonian Dynamics of the Stokes Parameters --

Starting with a Schrodinger-type equation derived from the Maxwell theory of electro- magnetism, a general formalism is presented for the change of light polarization in nonlinear birefringent media, which we call gyration or more generally, electromagnetic gyration and applications are considered. The theory is formulated in terms of the Hamil- tonian dynamics of the Stokes parameters which turns out to be the equation for a classical spin. As applications, we consider two models: (a) As the first application, we analyze solvable models admitting analytic solutions, which exhibit the structure change in the be- havior of the Stokes parameter caused by the mutual interplay between linear and nonlinear birefringence. (b) The second application is the optical analogue of the so-called nuclear magnetic resonance (NMR) or Rabi resonance. This is investigated in the case of purely linear birefringence and coexisting of linear and nonlinear birefringence.