W. A. Wozniak

Optical vortices generation using the Wollaston prism

A new setup of interferometers is proposed in which the set of specific optical markers--optical vortices--could be generated. The classical Mach-Zender two-beam interferometer has been modernized using the Wollaston prism. In this setup, the optical vortices could be obtained for a wide range of both beam parameters. The numerical analysis and experiments confirm our theoretical predictions.

Novel bifunctional systems for measuring the refractive index profile and residual stress birefringence in optical fibers and preforms

Two measuring systems are presented enabling determination of the refractive index profile and its anisotropy as well as principal stress components in optical fibers and preforms, respectively. The system for optical fibers is a scanning-type, differentiating interferometer used to measure directly the wavefront derivative, from which, after the inverse Abel transformation, the index profile is obtained. The required high sensitivity of measurement is achieved by applying the sinusoidal modulation of the input beam ellipticity and the homodyne detection of the first harmonic component of the output intensity. After removing the Wollaston prism, the system can be used to measure the retardation function that is related to the fiber residual birefringence. The dynamic spatial-filtering technique, used until now to measure the ray deflection function, has been modified for testing the preforms. An optionally applied linear modulator of ellipticity of the input beam was added, to enable the measurement of the retardation function also. The system can be easily switched from the measurement of the ray deflection function to the measurement of the retardation function by moving only a single element.

Performance analysis of a tandem of white-light fiber-optic interferometers

Abstract A white-light fiber-optic interferometric system composed of sensing and receiving interferometers separated with a dichroic-type linking interferometer was analyzed in order to determine the minimum group imbalance necessary to separate signal and noise patterns. For this purpose the analytical formulas for contrasts of the cross-interference patterns as well as the patterns produced by the sensing and receiving interferometers were derived. The contrast behavior was analyzed as a function of alignment at all coupling points and the dichroism of the linking interferometer. It is shown that the minimum group imbalance, which is the parameter responsible for temperature stability of the sensor, may be decreased to half for certain alignments.

Birefringence of gradient-index lenses of SELFOC® type

In recent 25 years a new kind of optical elements - gradient-index lenses, especially these of SELFOC type - meet with wide applications in many devices (photocopiers, compact disc players). Regardless of used in manufacturing of these lenses kind of technology, the nonuniformity of material (different doping concentration) and differences between the coefficients of linear expansion in the particular regions of the lens causes the internal stresses. Due to these stresses the gradient-index lens have to be considered as a birefringent medium. Anisotropy evoked by these stresses causes the splitting of the incident wavefront into two orthogonally polarized wavefronts and as a result: changing the image quality. The results of measurements of internal stresses and anisotropy for a few lenses are shown. The estimation of the split of the ordinary and extraordinary rays in these lenses and the numerical investigation of their diffraction image quality are presented.

The Numerical Investigation of Diffraction Image Quality of Gradient-index Lenses

A method for the exact calculation of the light intensity distribution in the focal plane of a gradient-index lens is presented. A modification is proposed based on a method exploited in classical systems of small aperture. The results of an investigation performed on selected lenses are shown.

Spatial elliptical polariscope for polarization distribution measurements

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.

Senarmont compensators with incorrect quarter wave plate and without calibrated quarter wave plates

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.

Transformation of polarization state of light using wave plates with arbitrary phase difference

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.

Interferometric characterization of side—hole fibers with elliptical core

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.

Multiple reflections in retardation plates with elliptical birefringence

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.