In this work we consider a microscopic optical system in which the beam with an optical vortex illuminates the sample.
The sample modifies the geometry of the vortex beam wavefront and the information about it is transferred into the
detection plane. It is shown that the beam at the detection plane can be represented by two parts: non-disturbed vortex
part and sample part. We propose and test a scheme for recovering the phase changes caused by sample inserted into
the vortex beam. The numerical simulations are supported by the experimental work.
Theoretical studies on Stokes polarimeter made of one twisted nematic crystal (TNLC) and one linear polarizer were carried out. Approaching the description of the TNLC theoretically, a model of Stokes polarimeter was created and its behavior was investigated in a numerical way. The minimization criterion of the condition number of the matrix describing the setup’s behavior was applied leading to the conclusion concerning the extension of the introduced by TNLC phase difference range up to 4π.
We consider a microscopic system in which the focused Gaussian beam with the embedded vortex illuminates the sample. The vortex beam is very sensitive to any imperfections introduced into it. Small defects introduced into the dark area of the vortex beam causes the change in its internal structure. We investigate theoretically and experimentally how the small rectangular groove introduced into the beam at the critical plane influence the phase structure of the beam. The analytical model of the setup is provided and following it the scheme for recovering the information about the sample is proposed.
The paper shows that the localization of a given light polarization state singularity of the optical field is strictly related to the elliptical analyzer properties. There are at least four reasons for such an approach: 1) there is an infinite number of light polarizations state representations; 2) the light polarization state cannot be measured directly; 3) non-measurable polarization state distribution of a light wave can be transformed into a measurable one using an elliptical analyzer; 4) the analyzer’s properties strictly determine the light polarization state representation. As a consequence, in my opinion, one cannot consider the properties of light polarization state singularities regardless of the analyzer’s polarization properties.
A new high sensitivity polarimeter has been established based on a fast change of the geometrical phase caused by a small change of an examined medium birefringence. In this setup sensitivity and measurement range can be controlled. The obtained sensitivity amounts up to 800 with regard to classical polariscopes. The proposed setup enables carrying out real time measurements. Stability and measurements resolution have been examined. Numerical simulations and measurements were performed.
Different types of singularities in the interference field of three plane waves with different polarization states are presented. As a result various types of singularities were found: isolated zero intensity points and polarization singularities of different types (depending on a chosen set of polarization parameters). The isolated zero intensity points form a specific rectangular lattice which turns into a hexagonal one when using the analyzer; an additional isolated zero intensity points appear as a result of interaction of the polarization singularities with the analyzer. The vortices observed in the phase pattern have topological signs equal to ± 1. More interesting are the polarization singularities present in the interference field without the analyzer. We observed the polarization singularities with different topological charges, −2 and + 1, for azimuth angle distribution and 0 for the diagonal angle distribution in the interference field of the three linearly polarized waves (LLL). In the case of the two linearly polarized waves interference and a third one circularly polarized (LLC) the polarization singularities with charge 0 were observed in the azimuth, ellipticity and diagonal angles distributions. We also noticed other characteristic points: saddles (for the ellipticity angle distribution in the LLL interference) and cross edge dislocations (for the phase angle distributions in both cases). Moreover, the zero intensity points in the setup without the analyzer appeared to be double singularities where both polarization parameters are undetermined simultaneously.
The device for the measurements of light polarization state parameters distributions has been presented. It consists of two
Wollaston like prisms (acting as spatial frequency generators), a linear analyzer, a CCD camera and a computer with the
specific software. The 2D Fourier transform of the recorded output intensity distribution contains two nonzero carrier
frequencies. The areas around these frequencies carry the information about the azimuth and the ellipticity angles
distributions of the examined light assuming that the variations of these parameters are with the frequency much lower
than the analyzer's carrier frequencies. Applying the Fourier transform methods of masking, shifting and inverse Fourier
transform with regard to these two areas, one can receive the wanted light polarization state distributions. The main
merits of this technique are: (1) the reconstruction of the polarization parameters distributions from one recorded output
image only, (2) the setup's compactness and no movable or electronically driven components. The paper presents the
setup details, critical points of adjusting setup procedure and numerical analysis, as well as the theoretical and
experimental results for uniform and non-uniform examined waves. The accuracy of the tests was estimated as λ/100.
We present a setup established to measure the light polarization state based on the general concept of Stokes
polarimeter. This setup consists of two liquid crystal modulators (LCMs), linear analyzer and CCD camera connected to
PC computer. Using this polarimeter all two-dimensional distributions of main polarized light parameters can be
measured. The measurement process consists of six fast intensity distributions measurements. In addition to the setup
description we discuss also the ways of the angular justification of both LCMs elements as well as the proper selection of
the LCMs' input voltages. The results of the measurement of some exemplary uniform and non-uniform polarized light
distributions are presented.
We propose a new setup established to measure the light polarization state and the birefringent media parameters. This
setup consists of two pairs of the linear Wollaston compensators and special circular compensators which form a set of
two spatially modulated elliptical compensators. These compensators can be used separately as a spatial generator of all
polarization states and as an elliptical spatial analyzer. When analyzing the light polarization state the singular minimum
points in the output light intensity appear. The coordinates of these points depend linearly on the azimuth and ellipticity
angles of the examined light. When combining both elements (generator and compensator) we can obtain a special
spatial elliptical polariscope. It allows measuring the main birefringent media parameters: the azimuth and the ellipticity
angle of its both eigenvectors as well as the phase difference, introduced by this medium. All desired quantities could be
obtained by some simple intensity measurements and neither movable parts nor active elements are needed and no
complicated analysis of output light should be made. We propose also a modification of described setup by using
different shearing angles in Wollaston compensators used in generator and analyzer. This should allow using Fourier
analysis of the output intensity distribution and makes our devices more suitable to real time measurements.
The present work shows a simple polariscopic module which enables measurements of optical properties of objects with
the micrometer order dimensions. The main part of this setup consists of polarizing elements - polarizers and Wollaston
prisms. The waves generating the vortex lattice leaving the polariscopic module are inclined to each other and they
constitute a four-point scanning system in the focal plane of the objective. Having measured the lattice shift or/and
deformation, one can determine object's different properties. The setup can work in both the transmission and reflection
mode. In the paper the theoretical background, numerical simulations and experimental results are presented.
We present the results of birefringent media properties measurement using two different interferometers with polarizing
elements. These setups allow to generate regular and stable lattice of optical vortices (OVs) and to record the lattice
deformations caused by introduced birefringent plate. The first setup is a polariscope arrangement with two Wollaston
compensators placed between crossed polarizers. The shape of lattice basic cell is determined by the Wollaston's
shearing angle and examined birefringent medium causes only the shift of the whole OVs lattice. The calculated
displacement vector allows determining at least two parameters of measured medium simultaneously. This setup was
used also to measure the absolute value of the phase shift introduced by examined birefringent sample by using two light
sources with slightly different wavelength. We manage to determine the phase retardance order by tracking the center of
two interferograms made with and without sample. The second setup is based on modified Mach-Zehnder interferometer
in which the Wollaston compensator is inserted into the one of interferometer's arm. The measured birefringent medium
placed in another interferometer's arm causes the mutual displacement of two OVs sublattices with different topological
signs. Calculated displacements vectors between those two sublattices allows to determine birefringent sample
parameters.
In this paper the two-wavelength procedure for determining of the birefringence medium phase retardance order using
the optical vortex birefringence compensator (OVBC) is presented. The OVBC generates regular optical vortex lattice
which moves if the measured birefringent medium is placed into the compensator setup. Due to the vortex lattice
regularity, tracing the lattice shift after the measured medium is inserted, there is no possibility to determine the absolute
phase retardance in the monochromatic light. This is an analogy to the well known problem in the classical fringe
interferometry. Having recorded interferograms for two waves with slightly different wavelengths, one can identify the
centers of the two pairs of interferogram images (with and without the examined medium in the setup) and hence in that
way the absolute shift of the vortex lattice. In the paper the theoretical considerations, numerical simulations, as well as
the analysis of the interferograms taken from the experiment are presented.
We present the imaging polarimetry method with phase shifting. The use of a liquid crystal modulator makes this method equally as quick as the one of imaging polarimetry with carrier frequency. This work presents a simple optical arrangement, together with the liquid crystal (LC) calibration procedure and experimental results confirming the correctness of the method and its accuracy.
In this paper some possible applications of a new device - Optical Vortex Birefringence Compensator (OVBC) are
proposed. The arrangement consisting of two Wollaston prisms placed between the linear polarizer and analyzer allows
to generate regular and stable optical vortex lattice. Inserting the measured medium into the OVBC can result in either
the deformation or the displacement of obtained vortex lattice. Tracing the lattice shift or its geometry changes after the
inserting the measured medium one can measure its optical properties. The main applications of the presented setup seem
to be the measurements of the angular deformation of the wave front and the properties of the linearly birefringent
media. In the paper the numerical simulations as well as the analysis of the interferograms taken from experiment are
presented.
The rule for both known magneto-optic effects in isotropic media is presented. It is a generalization of Faraday and Cotton-Mouton effects. This generalization includes any orientation of external magnetic field with regard to the light wave propagation direction. Also the formulae for total birefringence in medium placed within magnetic field has been given.
The first purpose of the article is to discuss the Senarmont method of the measurement of the phase difference of the birefringence medium, which is effective even if the quarter wave plate with the phase shift different from 90 degrees is used in the measurement setup. And also the modification of the Senarmont compensator is presented in the second part of this paper. It uses standard simple and reverse Senarmont setups, however, the phase retardances of unknown medium as
well as the element used as a quarter wave plate in classical setups could be measured.
The application of the Senarmont compensator setup for measuring of elliptically birefringent media properties is presented. The measurement procedure is carried out in two steps. In the first one, the medium is treated as a linearly birefringent, while, after a little modification of the measurement setup, is treated as a circularly one. Formulae for the phase shift introduced by the medium and the ellipticity angle of the first eigenvector of the medium are presented, also in the case when the quartenvave plate does not introduce the phase shift that is equal exactly 90°.
The practical problem of the lack of quarterwave plate for arbitrary wavelength has been solved. It has been shown that is possible to substitute this plate with a combination of two phase plates with phase shift different from 90 degrees. Some formulae have been derived for several of the most important cases of wave plates application in measurement setup. All the formulae are valid for arbitrary phase difference of component plates.
Side-hole fibers are one of the most hopeful types of fibers applied in pressure measurements. They have high sensitivity to pressure due to the presence of two air channels placed symmetrically near the circular or cylindrical core. In this paper, results of research of side-hole fibers with elliptical core are presented. The beat lengths of these fibers as well as the pressure and temperature sensibility were measured. The pressure sensibility reached 150 rad/MPa(DOT)m for the most sensitive fiber; that is a value 15 times greater than the sensitivity of standard birefringent fibers. Relation between the pressure and temperature sensitivity seems to be hopeful also, because their quotient was about 100 K/MPa for most of examined fibers.
The theory of elliptic retardation plates that takes into account a phenomenon of multiple reflections is presented. An analytical form of transition matrix for the normally incident plane wave is shown. Sample calculations of phase shift introduced by quartz retardation plates and of the output beam parameters as a function of plate thickness and optical axis orientation were done.
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