The paper proposes a method for finding the characteristics of the birefringence in optical media that possess several types of anisotropy simultaneously. It is proposed to characterize birefringence ...by a vector equal to the Stokes vector of the eigenpolarization multiplied by the phase shift between waves with eigenpolarizations. It is shown that such a vector of the complex birefringence is equal to the sum of such vectors corresponding to the component birefringences. The proposed method is well compatible with approaches to finding the polarization dynamics of propagating radiation based on the concepts of the Jones matrix and the Poincaré sphere.
A cycle of works on manufacturing and studying laser and magnetooptical ceramics with a focus on their thermo-optical characteristics performed by the research team is analyzed. Original results that ...have not been published before such as measurements of the Verdet constant in the Zr:TAG, Re:MgAl2O4, and ZnAl2O4 ceramics are also presented.
Magnetoactive materials are of considerable current interest, primarily for applications in nonreciprocal Faraday devices used for polarization control, optical isolation, optical switching, and ...modulation. The need for such devices is growing with laser power enhancement. They reduce risk of self-excitation of the amplifiers and optical elements damage and are a handy tool for organizing multipass schemes. However, at high average power of radiation these devices are subject to thermally induced effects that impair their operability and lead to increased losses and to the formation of phase distortions in the transmitted radiation. One of the methods to reduce thermally induced effects is to use in Faraday devices new magnetoactive materials with better thermo-optical properties. This paper is devoted to the study of thermo-optical and magneto-optical characteristics of a unique magnetoactive material-a terbium scandium aluminum garnet (TSAG) crystal. The TSAG has an extraordinary value of optical anisotropy parameter ξ, a Verdet constant 25% higher than the traditionally used terbium gallium garnet crystal and the highest magneto-optical figure-of-merit known in magnetoactive materials at the moment.
Thermally induced distortions of laser radiation caused by the photoelastic effect during high-power beam propagation through optical elements cut along the optical axis of uniaxial crystals have ...been investigated. Thermo-optical characteristics for uniaxial crystals of all three syngony types have been introduced: the optical anisotropy parameter ξ defining the distribution of the axes of thermally induced birefringence over the cross section of the optical element, and the thermo-optical constants Q and P specifying the value of thermally induced depolarization and thermal lens strength, respectively. The introduced thermo-optical characteristics may be used as applicability criteria of various uniaxial crystals for work with high-power laser radiation. The optical anisotropy parameter ξ of trigonal and hexagonal crystals has been found to be equal to unity by virtue of the isotropy of their piezo-optical properties in a plane perpendicular to the optical axis. We have analyzed by way of example thermally induced polarization distortions in a tetragonal DKDP crystal and in a trigonal CeF 3 crystal. The distributions and dependences observed in experiment fully agree with the theoretical considerations.
The polarization distortions of radiation, which arise when it passes through optical elements cut from uniaxial crystals in the regime of strong thermally induced birefringence, are studied. The ...presented theoretical description of the effect convincingly corresponds to the results of the experiment carried out for verification purposes. The problem of the existence of critical orientations of crystallographic axes in an optical element, at which polarization distortions do not occur, is studied for uniaxial crystals of all symmetry groups. Criteria for the existence of critical orientations are defined; approaches to finding these orientations are presented.
A magneto-active terbium containing cubic zirconia crystal is an attractive material for creating Faraday isolators thanks to a high value of its Verdet constant and low absorption coefficient. The ...optical anisotropy parameter of this crystal which shows the distribution of orientations of the axes of thermally induced birefringence in a thermally loaded optical element has negative value. It means that there exists a dedicated orientation of crystallographic axes, at which the axes of thermally induced birefringence are arranged in the one direction and thermally induced depolarization may be reduced substantially. For assessing potential of this crystal for high-power applications we have investigated its temperature dependence of the Verdet constant that proved to correspond to the paramagnetic behavior. Thermo-optical characteristics are also of principal importance when operating with high-power laser radiation. We present results of measurements of thermo-optical characteristics Q and P which determines values of polarization and phase distortions of passing laser radiation. Measured values can be used to determine the characteristics of Faraday isolators based terbium containing cubic zirconia crystals in various implementations of their optical schemes for various parameters of laser radiation.
In the presented work, the prospects for using pure ZnS and CdSe semiconductors for the development of Faraday isolators are investigated. Both materials have advantages over conventional ...magnetoactive materials. Their use can make it possible to expand the spectral range, in which isolators for high-power laser radiation can be implemented, both in the long-wavelength and short-wavelength regions. Measurements of the Verdet constant of crystals and the dependence of thermally induced depolarization caused by stress-induced birefringence on laser power were carried out. Based on the obtained experimental data, the parameters of the magneto-optical figure of merit were determined. The studied samples showed promising results, while the potential for increasing the magneto-optical figure of merit by optimizing the parameters of the production process is assessed as high. This possibility is illustrated by the example of ZnSe crystal samples obtained in various technological processes.
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A Faraday isolator with a square magneto-optical element is proposed and investigated. It is shown that the device has better isolation ratio and higher level of maximal operating power over ...conventional isolators with a round aperture when used in high-power laser systems with a square profile of beam intensity distribution.
A method for measuring thermo-optical characteristics of cubic crystals having arbitrary known orientation has been developed. Unlike the traditional techniques, it does not demand samples of ...specified orientation that greatly expands the scope of its applications and frequently makes it indispensable when novel optical media should be investigated. Experimental verification of the technique using a well-studied TGG crystal shows a convincing agreement between the results obtained by the new and the conventional methods.
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