Orthogonal Eigenpolarizations Research Articles

Design and experimental verification of a monolithic complete-light modulator based on birefringent materials

This paper presents a method to design a monolithic complete-light modulator (MCLM) that fully controls the amplitude, phase, and polarization of incident light. The MCLM is made of birefringent materials that provide different refractive indices to orthogonal eigen-polarizations, the ordinary o and extraordinary e states. We propose an optimization method to calculate the two relief depth distributions for the two eigen-polarizations. Also, a merging algorithm is proposed to combine the two relief depth distributions into one. The corresponding simulations were carried out in this work and the desired light distribution, including information on amplitude, phase, and four polarization states, was obtained when a laser beam passed through a 16-depth-level micro-structure whose feature size is 8 μm. The structure was fabricated by common photolithography. An experimental optical system was also set up to test the optical effects and performances of the MCLM. The experimental performance of the MCLM agrees with the simulation results, which verifies the validity of the algorithms we propose in this paper.

Characteristic Features of the Solution for the Inverse Problem of Polarimetry, Based on the Generalized Equivalence Theorem

We consider the characteristic features of the solution for the inverse problem of polarimetry for an arbitrary homogeneous anisotropic object, based on the generalized equivalence theorem. We show that in the general case, this problem has two solutions corresponding to the polarization basis sets, in which the amplitude and phase anisotropy matrices are not mixed. Using the solutions obtained, we carry out a comparative analysis of the conditions for realization of elliptical amplitude anisotropy with orthogonal eigenpolarizations (Hermitian dichroism) and we show the effect of these conditions on the characteristics of the eigenpolarizations. In both solutions, the orientation of the eigenpolarization is determined by the azimuth of the linear amplitude anisotropy and the ellipticity angle of the eigenpolarizations does not depend on the azimuths of the linear amplitude and phase anisotropy. The dependences of the ellipticity angle of the eigenpolarizations on the parameters of the amplitude anisotropy are different in these two solutions. The ellipticity angle depends on the magnitude of the type of amplitude anisotropy for which the matrix is first represented in this basis. The magnitude of the second type of amplitude anisotropy determines only the rate of change in the ellipticity angle.

Generalized non-local surface susceptibility model and Fresnel coefficients for the characterization of periodic metafilms with bianisotropic scatterers

A non-local surface susceptibility model for the consistent description of periodic metafilms formed by arbitrarily-shaped, electrically-small, bianisotropic scatterers is developed in this paper. The rigorous scheme is based on the point-dipole approximation technique and is valid for any polarization and propagation direction of an electromagnetic wave impinging upon the metafilm, unlike existing approaches whose applicability is practically confined to very specific cases of incidence. Next, the universal form of the resulting surface susceptibility matrix is employed for the derivation of the generalized Fresnel coefficients for such surfaces, which enable the comprehensive interpretation of several significant, yet relatively unexamined, physical interactions. Essentially, these coefficients include eight distinct terms, corresponding to the co-polarized and cross-polarized reflection and transmission coefficients for the two orthogonal eigenpolarizations of a linearly-polarized incident plane wave. The above formulas are, then, utilized for the prediction of the scattering properties of metafilms with different planar and non-planar resonators, which are characterized via the featured model and two previously reported local ones. Their comparison with numerical simulation outcomes substantiates the merits of the proposed method, reveals important aspects of the underlying physics, and highlights the differences between the various modeling procedures.

DOMINANT TYPE OF DETERMINISTIC POLARIZATION TRANSFORMATION FOR INHOMOGENEOUS ELLIPTIC BIREFRINGENT MEDIUM

The features of spectral properties of the Jones matrix model of the dominant deterministic polarization transformation for inhomogeneous elliptic birefringent medium have been studied. It is shown that in the case when azimuths of linear dichroism and linear birefringence are coincide the arbitrary Jones matrix can not be characterized by orthogonal eigenpolarizations.

Eigenanalysis of dichroic, birefringent, and degenerate polarization elements: a Jones-calculus study

A theoretical analysis of eigenpolarizations and eigenvalues pertaining to the Jones matrices of dichroic, birefringent, and degenerate polarization elements is presented. The analysis is carried out employing a general model of a polarization element. Expressions for the corresponding polarization elements are derived and analyzed. It is shown that, despite the presence of birefringence, a polarization element can, in a general case, demonstrate a totally dichroic behavior. Moreover, it is proved that birefringence necessarily accompanies dichroic elements with orthogonal eigenpolarizations. A transition between degenerate, dichroic, and birefringent eigenvalues is studied, and examples of synthesis of polarization elements are given.

Polarization control of vertical-cavity surface-emitting lasers through use of an anisotropic gain distribution in [110]-oriented strained quantum-well structures

An analysis of the in-plane optical matrix elements connected with the gain distribution of (In,Ga)As-GaAs quantum-well structures on [110] GaAs substrates is presented. The in-plane gain distribution is found to be anisotropic-with a maximum directed along the [110]-[110] crystallographic axis. Optically-pumped vertical-cavity surface-emitting lasers on the [110] surface with these quantum wells in the cavity exhibit stable, well-defined polarization states; this stability is believed to be a consequence of the predicted anisotropic gain distribution on the [110] surface. Of the two orthogonal eigen polarizations observed, the one with the higher optical intensity, for a given pump power, was found to be stabilized along the [110] crystallographic axis; this is in agreement with the analysis. >

Gain-dependent polarization properties of vertical-cavity lasers

We show that the partitioning of power into the two orthogonal eigen polarizations of infra-red gain-guided vertical cavity lasers depends upon the relative spectral overlap of the nondegenerate polarization cavity resonances with the laser gain spectrum. Furthermore, at the condition where the polarization resonances and the peak laser gain are aligned, abrupt switching of power between the eigen polarizations is observed as the gain sweeps through the polarization resonances. The gain-dependence of the polarization requires spectral splitting between the eigen polarizations, which is found to be strongly influenced by local strain. The polarization of the fundamental and higher-order spatial modes can be selected and maintained for all InGaAs vertical-cavity lasers in a wafer simply by employing a 20 nm or greater blue-shift offset of the peak laser gain relative to the cavity resonances. >

Homogeneous and inhomogeneous Jones matrices

The classification of polarization properties of polarization elements is studied to derive data-reduction equations for extracting the diattenuation, retardance, and other polarization properties from their Jones matrices. Polarization elements, and Jones matrices as well, are divided into two classes: homogeneous, with orthogonal eigenpolarizations, and inhomogeneous, with nonorthogonal eigenpolarizations. The basic polarization properties, diattenuation and retardance, of homogeneous polarization elements are straightforward and well known; these elements are characterized by their eigenvalues and eigenpolarizations. Polarization properties of inhomogeneous polarization elements are not so evident. By applying polar decomposition, the definitions of diattenuation and retardance are generalized to inhomogeneous polarization elements, providing an understanding of their polarization characteristics. Furthermore, an inhomogeneity parameter is introduced to describe the degree of inhomogeneity in a polarization element. These results are then adapted to degenerate polarization elements, which have only one linearly independent eigenpolarization.

Polarization properties and frequency stabilization of an internal mirror He-Ne laser emitting at 543.5 nm wavelength

Frequency stabilization to the gain profile of an internal mirror He−Ne laser emitting at 543.5 nm wavelength is described. The dependence of the power and polarization on frequency was investigated for multi-mode and two-mode operation. The emitted laser modes are linearly polarized. Two orthogonal eigenpolarizations fixed to the laser tube were observed. Spontaneous switching between these polarizations occurred when the laser frequency was scanning through the gain profile. In two-mode operation, these polarization flips have been suppressed by applying a weak magnetic field transversal to the gas discharge. Under such operation conditions the frequencies of the laser could be stabilized to the gain profile by controlling the power difference of the two modes to zero. The fractional frequency reproducibility is in the region of Δf/f≃3×10−8.