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.
We present a new method for the measurement of a residual birefringence in a polariscopic interferometer. Measured
medium inserted into the setup can cause the changes in the polarization state of the propagated beam. Specific
orientation of the elements (i.e. the analyzer and the phase retarder) modifies the setup response to the small changes of
the azimuth and ellipticity angles of the propagated beam - the sensitivity of the setup is highly increased within the
limited measuring range. The sensitivity and the measuring range of the setup can be adjusted by proper mutual
orientation of the setup elements. Even though the measurement requires the analysis of the low contrast interferograms,
what can be difficult, the application of the Fourier analysis allows the calculations for the interferogram contrast lower
than in case of classical interference pattern shift tracking. In the present paper both theoretical considerations and
experimental results taken from the experimental model setup are presented. Hundredfold increase in sensitivity was
obtained in the presented experiments, which allowed the measurement of phase difference introduced by the
birefringent medium with an accuracy of one hundredth degree.
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.
The application of the optical vortex interferometer (OVI) to small-angle rotation measurements is presented. The OVI is based on a regular lattice of optical vortices. In our experimental setup a regular lattice of optical vortices is produced by the interference of three plane waves. The vortex points are stable, pointlike structures within the interference field. Distortion of one, two, or three of the interference waves results in a characteristic vortex lattice deformation. This deformation can be measured and related to the physical quantities being investigated. We show the ability of the OVI to measure the deflection angle and the orientation of the wave vector in a single measurement. Two different methods that allow comparing the geometry of the vortex lattice are used to analyze the results of the experiment. They are compared with the method based on standard two-beam interferograms. The results show that the OVI system can be successfully used to measure the deflection and orientation of the wave vector. The vortex methodology is more accurate than classical two-beam interferometry for rotation angles in the range of a few arcseconds.
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.
In this work the application of the Optical Vortex Interferometer (OVI) to small-angle rotation measurements is
presented. OVI is based on the regular net of optical vortices. In our experimental setup a regular net of optical vortices
is produced by the interference of three plane waves. Distortion of one, two or three of the interference waves results in
a characteristic vortex net deformation. This deformation can be measured and related to the physical quantities being
investigated. In the given paper we present the ability of the OVI to measure the deflection angle of the wave vector and
its orientation in a single measurement. Two different methods which allow for comparing the geometry of the vortices
net were used to analyze the results of the experiment. They were compared with the method based on the standard two
beam interferogram analysis. The results show that the OVI system can be successfully used to measure the deflection
and orientation of the wave vector. The vortex methodology is more accurate than classical two beam interferometry in
the case of the rotation angles in the range of few arcseconds.
Assuming that the Compton phenomenon is mainly responsible for the scattering in the block of metal, there was
calculated the deposit of radiation at the bottom of the cylinder originating from its wall. The calculation was made for
the primary spectrum 0 - 6 MeV given for Clinac accelerator. Klein - Nishina relations were taken as describing an
elementary scattering event. The radiation intensity recorded on photographic material was compared to that evaluated as
the incoherent summation of contributions. Supposing the caustics arising it was shown the possibility of the change of
the intensity distribution.
Optical Vortex Interferometer (OVI) is a new type of interferometer which is based on the regular net of optical vortices (OV)1,2,3. The net is generated by the interference of three plane waves. The idea of the measurement with the OVI is as follows: if one of the interfering waves is distorted then the geometry of the vortex net is changed. In our case one of the wavefronts was tilted. We can calculate the tilt of the wave by tracking the change of vortices positions. Basically it is sufficient to determine the relative change in the positions of three optical vortices (vortex triplet). If there are 200 vortices in the measurement field then we can choose about 1 million vortex triplets. The important advantage of this measurement is that two rotation angles through two perpendicular axes can be determined into one step. Also the mechanical vibrations are automatically subtracted and the system is simple.
Our first results show5 that using about 1000 triplets we can measure the small angle with an error of 1.2arcsec (on the base of standard deviation). Performing the analysis we observed however that the real sensitivity of the OVI is higher than resolution resulting from the basic analysis methods. We observe the change of the histogram of the calculated angle if the tilt by the angle of 0.05arcsec is introduced. In the paper we analyze this effect. If the rotation angle is small then optical vortices change their positions by the small part of the distance between the measurement points. Due to detector quantization some of vortices can be still localized as lying in the same measurement point while the others are localized as shifted. This effect causes the histogram shift. The method of recomputing such histogram shift into the value of rotation angle is presented. In result we can achieve 6-10 times better resolution of the OVI.
We present one of the applications of the Optical Vortex Interferometer (OVI). OVI is based on the regular net of optical
vortices which are generated by the interference of three plane waves. Disturbing one of the interfering waves causes a
change in the position of the vortex points in the vortex net. The measurement is based on tracking the vortex position
change. This method can be used to determine small-angle rotation. OVI distinguishes two axis of rotation and the
corresponding two rotation angles can be measured with sub-second resolution. The linear vibrations of the measured
element are automatically subtracted. The single measurement provides hundreds of measurements points, so the
statistical methods for data analysis and corrections can be effectively applied. In the paper we present the experimental
testing of the method. To get the precise rotation of one of the interfering wave's the optical wedge is put into one of the
interferometer's arm. The analysis shows that the amplitude`s decrease does not influence the measurement accuracy.
From the vortex net shifting the rotation angle of one of the interfering waves is calculated and this rotation is also used
to calculate the refracting angle of the applied optical wedge.
The goal of this paper is the analysis of the wavefield in the vicinity of the simple two dimensional caustics. The caustics and the focuses are the objects of interest of many technical applications.
Ten years ago it seemed that due to packets of the special functions stored in memory of computer evaluation of the field in the caustic area and in focuses will become the simple procedure. Nothing such occurred excepting the access to the special functions. On the example of the simplest case the caustic with one cusp was shown how the problem of evaluation of the amplitude may be overcome.
For the appearing of caustics are responsible the concave fragments of the wavefront. From many possibilities we choose to consider the concavity which produces at the plane closing it cosine phase function (formula in paper)and the unity amplitude. Thus, our elementary task is simplified to the niche, which acts as cosine phase filter. The calculations were carried out on the cross section from the caustic to their asymptote using several methods. The first rough estimation was obtained on the grounds of knowledge of created caustic type and focusing index. Then it was shown as the stationary phase method which fails in this region is helpful besides of overlapping of active regions. The obtained results were compared with these obtained due to Kirchhoff s integral.
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