Parameters Of Polarization State Research Articles

Suppression of vortex electromagnetic wave divergence by modulating the wave front dislocation line

Abstract When the beam is transmitted in the atmosphere, under the influence of atmospheric turbulence, the beam will occur energy attenuation, wavefront distortion and other phenomena, which will seriously affect the transmission and reception of information. Based on the PB phase principle enhances the focusing capability of the auto-focusing Airy Gaussian vortex beam by regulating the wavefront error curvature of the vortex beam, and then enhances the resistance of the beam against atmospheric turbulence. The results reveal the curvature of the wavefront error curve and the peak intensity of the light field of the beam can be changed by changing the beam polarization state parameters n and m in the focal plane. The auto-focusing Airy Gaussian vortex beam with the polarization state parameters m=1, n=4 increases the peak magnitude of the light field intensity in the focal plane of the auto-focusing Airy Gaussian vortex beam with the polarization state parameters m=0, n=0 to 1.99 times. Demonstrate that geometric phase tuning the auto-focusing Airy Gaussian vortex beams can enhance resistance to atmospheric turbulence. Furthermore, this paper extends this method to the field of millimeter wave. Under the transmission distance of 1km, the peak intensity of the initial vortex electromagnetic wave after the geometric phase adjustment is increased to 3.33 times, and the receiving radius of the target surface is reduced to 0.24 of the initial vortex electromagnetic wave. It shows that geometric phase-regulated vortex electromagnetic wave can suppress vortex electromagnetic wave divergence and have potential applications in wireless communication.

Polarization properties of partially coherent mixed dislocation beams transmitting in biological tissues

<sec> <b>Objective</b> The optical information change of beams acting on biological tissue can get an insight into the new optical effects of tissue, and even can provide a theoretical basis for developing biphotonic medical diagnosis and therapy technologies. Polarization technology is also widely used in the field of biological detection due to its advantages of non-contact, rich information and without staining markers. In this work, the polarization behaviors of partially coherent screw-linear edge mixed dislocation beam transmitting in biological tissue are analyzed and explored. Simultaneously, in order to more clearly and more intuitively understand a mixed dislocation beam, both the normalized intensities and phase distributions at source plane for different parameters <i>a</i> and <i>b</i> are also discussed. We hope that the obtained results will provide theoretical and experimental foundation for expanding the application of singularity beams in biological tissue imaging technology.</sec><sec> <b>Method</b> By combining the Schell term with the field distribution of the screw-linear edge mixed dislocation beam at the source plane, and based on the generalized Huygens-Fresnel principle, the analytical expressions of the cross-spectral density matrix elements of partially coherent screw-linear edge dislocation beam propagating in biological tissues are derived. Adopting the unified theory of coherence and polarization, the polarization behaviors of the beams can be investigated in detail.</sec><sec> <b>Results</b> At the source plane, the intensity has a non axisymmetric distribution, and there exists a coherent vortex with a topological charge size of 1 and a linear edge dislocation. The sign of <i>a</i> is related to the rotation direction of the phase singularity. The larger the value of <i>b</i>, the farther the linear edge dislocation is from the origin. At the source plane, the degree of polarization and ellipticity between the two identical points are independent of the four parameters: dimensionless parameter <i>a</i>, off-axis distance of edge dislocation <i>b</i>, spatial self-correlation length <i>σ</i><sub><i>yy</i></sub>, and spatial mutual-correlation length <i>σ</i><sub><i>xy</i></sub>, the orientation angle is only independent of <i>a</i> and <i>σ</i><sub><i>xy</i></sub>; the polarization of two different points is independent of <i>a</i> and <i>b</i>, but is related to <i>σ</i><sub><i>yy</i></sub> and <i>σ</i><sub><i>xy</i></sub>. In transmission, the polarization degrees and ellipticity of two different points fluctuate greatly and the orientation angle displays less fluctuation. Finally, all the polarization state parameters tend to be their corresponding values, respectively.</sec><sec> <b>Conclusions</b> The results show that when <i>b</i> is smaller, the linear edge dislocation is paraxial and plays an important role in the polarization state change; when <i>b</i> is larger, the polarization state changes of the screw-linear edge mixed dislocation beam will tend to be the pattern of spiral beams. The absolute value of the difference between <i>σ</i><sub><i>yy</i></sub> and <i>σ</i><sub><i>xy</i></sub> is also one of main factors influencing the polarization state. The sign of <i>a</i> does not affect the change in polarization state, but its magnitude can influe the change of speed. Due to more complex factors determining the correlation fluctuations between different points in the light field, the changes of two different points are more sensitive than those of the two identical points in shallow biological tissue. Beams with different parameters can be selected for different application requirements.</sec>

Noninvasive polarization-based technique for hematocrit monitoring

Subject of study. Polarization images corresponding to the 2D distributions of polarization state parameters for light scattered by biological specimens with different hematocrit levels were obtained by shining laser light in a given polarization state of blood-containing tissue through the nail bed of the left fifth finger. Aim of work. The aim of this work is to determine whether active video polarimetry is suitable for noninvasive real-time monitoring of blood hematocrit and to develop data-based criteria to identify hematocrit levels corresponding to various body states of human test subjects. Method. Physical models of changes in the parameters of polarized radiation during interaction with a biological specimen are used. A prototype optical design was developed for a Stokes video polarimeter capable of recording the irradiance distribution within a single analysis field on the sensitive area of a photodetector array. The digital images were processed using the Stokes–Mueller matrix formalism. A comparative statistical analysis of the 3D distributions for various parameters describing the polarization state (degree of polarization and the azimuth and ellipticity of the polarization ellipse) was performed to determine whether it is possible to detect differences in the hematocrit levels of human blood. Main results. A new approach to noninvasive hematocrit monitoring based on optical polarization is proposed. We obtained 3D distributions and histograms of light polarization state parameters for two human test subjects known to have different hematocrits. Statistical analysis revealed that significant differences in the second–fourth order statistical moments of the light polarization parameters are the most relevant diagnostic indicators for comparative analysis of biological tissues having different blood hematocrit levels. Practical significance. With further development, the proposed method can be applied to both medical diagnosis and emergency treatment. Timely detection of significant deviations from the normal hematocrit based on automated calculation and analysis of the data parameters identified will enable continuous hematocrit monitoring during surgical operations and effective real-time adjustment of blood viscosity.

Measuring the Laser Polarization State and PBS Transmission Coefficients in a Heterodyne Laser Interferometer

By placing a polarizer between a dual-frequency laser source (DFLS) and a polarizing beam splitter (PBS), two optical beat signals are formed; then, the transmission coefficients of the PBS and the polarization state parameters of the DFLS can be simultaneously measured without coupling while achieving high accuracy. We obtained explicit equations for the ellipticity angles of the laser beam components and explained the relationship between the extreme values of the beat amplitude and the laser polarization state parameters, which obtain less uncertainties than the existing work. The method is validated experimentally. Measuring these parameters is important to compensate for nonlinearity errors in heterodyne laser interferometers and assess the quality of devices.

Size-dependent patterns in depolarization maps from turbid medium and tissue.

Mueller matrix measurements on turbid media can be used to quantify its polarization properties in terms of retardance, diattenuation, and depolarization. In particular, the depolarizing ability of such media, which is represented by the depolarization index, has been shown to be a useful diagnostic parameter. However, being a single valued metric, its dependence on a host of tissue optical parameters makes it difficult to interpret. In this paper, we show that a map of depolarization as a function of input polarization state parameters can be used to infer information about the size of scatterer and order of birefringent and depolarizing layers in turbid medium. The experiments carried out on different mice organ tissues indicate that the depolarization characteristics of tissue are closely represented by depolarization properties of intralipid. We also observed that these maps do not vary in the presence of absorption.

Full polarization measurement of SR emitted from twin helical undulators with use of Sc/Cr multilayers at near 400 eV

We carried out the full polarization measurements on highly circularly polarized light in soft X-ray region. The measurements were performed on synchrotron radiation of near 400 eV emitted from twin helical undulators at BL25SU in the SPring-8. All parameters of polarization state of the light were determined with a phase shifting transmission multilayer and a polarizing reflection multilayer. The phase shifter was a newly developed Sc/Cr multilayer and was evaluated as a quarter-wave plate. The results of full polarization measurement indicated that the twin undulators produced symmetrically circularly polarized light.

Polarization Parameters of a Reflector type Wire-Grid Polarizer

The polarizing properties of wire-grid polarizer, consisting of closely spaced, parallel metal strips etched on a metal backed dielectric sheet are investigated for a plane electromagnetic wave of arbitrary incidence and polarization. The structure can be designed to be used both as a linear polarization rotator and as a circular polarizer. The frequency characteristics of the polarization state parameters of the reflected wave have been studied. Also, experimental verification of the analytical result are carried out for a sample rotator.