Measurement of linear birefringence using a rotating-wave-plate Stokes polarimeter

In this study, a compact polarimeter is developed to measure the linear birefringence property of optical materials. The principal axis angle and the retardance are obtained by a simple signal-processing algorithm, which is derived via Stokes parameters extractions when using an incident light linearly polarized at 45°. There exists an absolute error of 0.0296° on average in the principal axis angle measurement and a relative error of 2.54% in the retardance measurement of a quarter-wave-plate sample with its principal axis ranging from −40° to 40°. The standard deviations for the principal axis angle and retardance measurements are determined to be 0.015° and 0.018°, respectively, while one standard deviation to the average value of the principal axis angle and retardance, respectively, are just 0.066% and 0.020% with high repeatability, and corresponding dynamic ranges of −45° to 45° and −180° to 180°, respectively. Consequently, the developed polarimeter has a potential in linear birefringence measurement, especially in the retardance measurement.     

The application of a rotating-wave-plate stokes polarimeter for measurement of the optical rotation angle

An optical scheme based on Stokes-Mueller formalism and rotating-wave-plate Stokes polarimeter is successfully developed to measure the optical rotation angle in a chiral medium. The average relative error in the measured rotation angle of a half-wave plate is determined to be 1.16%. The average relative error in the measured rotation angles of glucose solutions with concentrations ranging from 0 to 1.2 g/dl is determined to be 3.78%. The correlation coefficient between the measured rotation angle and the glucose concentration is found to be 0.99950, while the standard deviation is just 0.00376°. From the inspection of measured rotation angle in the sol-gel materials containing C₁₇H₁₇ClO₆ with concentrations ranging from 0 to 0.0665 g/ml, the average relative error in the measured rotation angles is determined to be 3.63%. Consequently, the derived algorithm for measuring the rotation angle of a chiral medium is feasible, and the developed system is evaluated with a precision of 5.4% approximately in rotation angle measurement.     

Plasmonic enhancement of linear birefringence and linear dichroism in anisotropic optical metamaterials

The resonant behavior of linear birefringence and linear dichroism spectra is found in anisotropic optical metamaterials made of noble metal thin films with stripes and rectangular hole nanoapertures forming one- or two-dimensional subwavelength gratings. Differences in effective refractive index and extinction coefficient for linearly polarized eigenstates are increased in spectral range of resonances of local and surface plasmon-polaritons at the normal incidence and reach the values of Δn ≃ 2.5 and Δκ ≃ 2.75, respectively.     

Error analysis and Stokes parameter measurement of rotating quarter-wave plate polarimeter

In this paper, we present a simple Stokes parameter measurement method for a rotating quarter-wave plate polarimeter.This method is used to construct a model to describe the principle of how the magnitudes of errors influence the deviation of the output light Stokes parameter, on the basis of accuracy analysis of the retardance error of the quarter-wave plate,the misalignment of the analyzing polarizer, and the phase shift of the measured signals, which will help us to determine the magnitudes of these errors and then to acquire the correct results of Stokes parameters. The method is validated by the experiments on left-handed circularly polarized and linear horizontal polarization beams. With the improved method, the maximum measurement deviations of Stokes parameters for these two different polarized states are reduced from 2.72%to 2.68%, and from 3.83% to 1.06% respectively. Our results demonstrate that the proposed method can be used as a promising approach to Stokes parameter measurement for a rotating quarter-wave plate polarimeter.     

Study on optical electron polarimeter and measurement of the relative Stokes parameters of weak light

In this paper, we present the research on an optical electron polarimeter, which is used to determine the polarization of an incident electron beam by measuring the relative Stokes parameters of the fluorescence emitted from the He gas following the impact excitation with the electron beam. The fundamental theory of the optical electron polarimeter is discussed with the 3³P→2³S transition of He. The structure and performance of the instrument are described, which are different in some aspects from previous works. The arrangement of the experiment for measuring the relative Stokes parameters of linearly polarized weak light is also investigated, which actually involves the same processes as the polarization measurement with the incident electron beam. The results obtained are in agreement with the theoretical prediction.     

Autocollimation polarimeter for measuring two-dimensional distribution of birefringence

Optics and Spectroscopy - A device for studying samples with nonuniform distribution of birefringence and corresponding measurement techniques are proposed. The optical arrangement of a polarimeter...     

Optimization of retardance for a complete Stokes polarimeter

We present two figures of merit based on singular value decomposition, which can be used to assess the noise immunity of a complete Stokes polarimeter. These are used to optimize a polarimeter featuring a rotatable retarder and a fixed polarizer. A retardance of 132 degrees (approximately three-eighths wave) and retarder orientation angles of +/-51.7 degrees and +/-15.1 degrees are found to be optimal when four measurements are used. Use of this retardance affords a factor-of-1.5 improvement in signal-to-noise ratio over systems employing a quarter-wave plate. A geometric means of visualizing the optimization process is discussed, and the advantages of the use of additional measurements are investigated. No advantage of using retarder orientation angles spaced uniformly through 360 degrees is found over repeated measurements made at the four retarder orientation angles.     

Internal magnetic field measurement in tokamak plasmas using a Zeeman polarimeter

In a tokamak plasma, the poloidal magnetic field profile closely depends on the current density profile. We can deduce the internal magnetic field from the analysis of circular polarization of the spectral lines emitted by the plasma. The theory of the measurement and a detailed design of the Zeeman polarimeter constructed to measure the poloidal field profile in the ADITYA tokamak are presented. The Fabry-Perot which we have employed in our design, with photodiode arrays followed by lock-in detection of the polarization signal, allows the measurement of the fractional circular polarization. In this system He-II line with wavelength 4686 Å is adopted as the monitoring spectral line. The line emission used in the present measurement is not well localized in the plasma, necessiating the use of a spatial inversion procedure to obtain the local values of the field.     

Study on the optically linear birefringence and dichroism properties of Fe3O4 magnetic nanoparticles

We adopt an improved co-precipitation method to prepare the Fe₃O₄ magnetic nanoparticles (MNPs). Influence factors such as the reaction temperature, the pH value of the solution, and the Fe³⁺/Fe²⁺ molar concentration are considered. Via the transmission electronic microscope and X-ray diffractometry, we characterize the dispersibility and size of the products. The reaction temperature and the pH value of the solution have a great influence in the dispersibility and size of MNPs. The diameter of Fe₃O₄ MNP, produced under Fe³⁺/Fe²⁺ molar concentration of 0.25 mole/l and molar ratio of 1.9:1, the reaction temperature is 80 °C, and the pH value reaches 9, is close to 11 nm. Above all, considering the variation of molar concentrations in Fe³⁺/Fe²⁺, the linear birefringence and dichroism of the kerosene-based ferrofluids are investigated by a Stokes polarimeter.     

Measurement of the degree of polarisation of thermally modified Scots pine using a Stokes imaging polarimeter

Optical Review - This study measured the polarised light reflected from the surface of thermally modified Scots pine (Pinus sylvestris L.) wood using a Stokes imaging polarimeter. The data were...     

Coupling effects between dichroism and birefringence of anisotropic media

The basic polarization properties of media are their dichroism and birefringence. In this work we report the possible consequences of the coupling effects between dichroism and birefringence of anisotropic media. Our analysis is based on a solution of the differential equation of the Stokes four-dimensional vector. It is shown that there exist three types of coupling effects between the components of the dichroism vector and birefringence vector of the medium. The conditions under which the polarization properties of a continuous medium can be calculated are identified. These results are helpful for any study involved an interpretation of the measured Mueller matrix of continuous anisotropic medium.     

Observation of magnetoelectric linear birefringence

We report the first experimental observation of optical linear birefringence induced in molecular liquids by crossed electric and magnetic fields perpendicular to the direction of light propagation. The optical axes coincide with the external fields, and the strength is bilinear in the electric and magnetic fields.     

The use of polarization modulation and amplitude-sensitive optical heterodyne interferometry for linear birefringence parameters measurement

A novel common-path polarization modulation and amplitude-sensitive optical heterodyne polarimeter is setup in order to characterize a phase retardation plate (PRP) in real time. The phase retardation ΔΦ and fast-axis angle β of the linear birefringence parameters (LBP) of a PRP are measured simultaneously. Meanwhile, the dynamic ranges of 0° < ΔΦ < 180° and 0° < β < 180° are demonstrated experimentally. In order to measure LBP in real time, a polarization modulation is introduced by continuously rotating the tested PRP such that ΔΦ and β are able to be obtained in terms of the ratio of the amplitudes of S polarization and the ratio of P polarization of the heterodyne signals, respectively. Consequently, this novel method, which combines optical heterodyne interferometry with a polarization modulation technique, not only improves the detection sensitivity, but also provides a real time capability to measure LBP. In addition, the error in the LBP measurement is derived and analyzed.     

电子束极化度测量仪及其电子学系统的研制

介绍了研制成功的电子束极化度测量仪的基本原理、结构及其电子学测量系统,该系统基于PC机的数据获取和处理,并实现了整个实验过程的自动控制.作为对电子束极化度测量仪及电子学测量系统性能的检验,实验测量了线偏振光相对Stokes参数.测量结果表明整个系统具有测量精度高、结构紧凑和性能稳定的特点.     

Sensitive birefringence measurement in a high-finesse resonator using diode laser optical self-locking

We demonstrate a new method to measure weak birefringence of dielectric mirrors with excellent spatial resolution and sensitivity (<10^-7 radians). We exploit a well-known optical feedback scheme for line-width narrowing and frequency locking of a diode laser to a high-finesse cavity. Feedback comes from the intracavity field which builds up at resonance, selected by its change in polarization with respect to the incident field. This change, due to the residual birefringence of the cavity mirror coatings, was already exploited for birefringence measurements using an active laser-locking scheme. Here we measure the optical feedback rate as a function of rotation angle of one of the cavity mirrors (around the cavity axis). A stable feedback signal is obtained since the laser, as soon as it locks to a cavity resonance, effectively behaves as a monochromatic source. By fitting the data with a theoretical expression, we determine quantitatively the local birefringence vectors of both mirrors, which are around 10^-6 radians. Our scheme is simple, works with cavities of very high finesse (F∼10⁵), and is promising for measuring birefringence in gases induced by external fields. Received: 18 July 2001 / Final version: 14 March 2002 / Published online: 8 May 2002     

Magnetic linear birefringence of europium-gallium garnet

The magnetic linear birefringence of Eu₃Ga₅O₁₂ in the 78–295 K temperature range is investigated experimentally and theoretically. Good qualitative agreement between the theoretical and experimental temperature dependences of the magnetic linear birefringence is obtained. The magneto-optical anisotropy of Eu₃Ga₅O₁₂ is analyzed and it is shown that here there is only qualitative agreement between theory and experiment. Moscow State University Institute of Electronic Techniques. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 83–86, April, 1997.