Temperature On The Impact Of The Birefringent Crystal And The Polarizing Device

Polarizing technology has got the development at full speed with the development of laser and photo-communication technology. And the development key is polarizing devices which often play a mutual role with outfield during the process of employing, temperature field can't be escaped by any polarizing devices, the refractive indices of the crystal and shape of face,etc. should be changed because of the change of temperature among them, that cause splitting beam angle , deviating angle, sheared difference, transmittance ratio and extinction ratio changed, thus influence the optical performance of the devices.This thesis mainly takes Calcite crystal and quartz crystal as an example, temperature characteristic and the temperature effect of splitting beam angles of Wollaston prism of two kinds of crystal have been studied, that have offered the theory and experiment basis for use of prism at different temperature. The full text includes the following contents briefly:In the first chapter, we mainly introduce the general development of polarizing devices and temperature effect of crystal, and explain the work of this thesis.Chapter two recommend the basic theories of polarizing devices at first, and make a brief introduction of crystal materials;Then Snell formula ,thermal expansion and acquisition methods of polarized light are drawn into;At last several kinds of daily polarizing prisms are introduced .In chapter three, firstly, the materials properties of the Calcite crystal are described and the notion of the chromatic dispersion and Sellmeier equation are presented.;secondly, constants expression of Sellmeier equation are analytically calculated out, then the expression of the thermo-optical coefficients at different wavelength are got by curve-fitting means, by which we obtain the refractive indices corresponding in different wavelength under each temperature. Comparing its value with the value offered by the literature [18 ], we findSellmeier equation has well expressed the relation of chromatic dispersion of Calcite crystal. Thus a method for asking the refractive indices of crystal is offered.Chapter four is a key part and also is the innovation in this thesis. The temperature effect of Wollaston is carried on the research in detail: firstly, the experiment system of measuring the temperature effect is established and the Calcite Wollaston prism is test by it. We find theory calculation and experimental result are not identical only considering the change of the refractive indices, the experimental result reveals: with the temperature rising, the splitting beam angle of o light (regarding first prism as reference) drops quickly, while that of e light does not basically change. In theory, the situation of o light and e light is exchanged. For proving the accuracy of experimental result and theory calculation, we design the temperature effect experiment of the right angle prism, and find it is similar to Wollaston prism. That splitting beam angle is a function of refractive indices and structural angle is founded out from the formula of splitting beam angle of the right angle prism, so we design the following experiments to prove the accuracy of refractive indices and the degree of influence on structural angle by temperature, at first, we measure the main refractive indices and thermal-optical coefficients of Calcite crystal by auto-collimation method, and find the measurement value is identical with the value offered of the literature [18 ] to 10-4 at the room, but there is a greater deviation while temperature intensifying;then we design the temperature effect of OE double output prism experiment to prove the structural angle varying with temperature and find the structural angle varies with temperature greatly. So, we obtain: The influence of temperature on the splitting beam angle of prism relate to not only the change of the refractive indices, but also the change of the structural angle.We measure structural angles of Wollaston prism and right angle prism in every temperature point again after considering the change of structural angle by the change of temperature, through theory calculating, we find the theory valuesof the splitting beam angle of both right angle prism and Wollaston prism accord with experimental values well in this way. We also find that the structural angle varied with temperature should be considered when the refractive indices of Calcite crystal is measured , thus the measurement value is identical with the value offered by literature [18 ] to 10-4 when temperature rise. Then the Wollaston prism temperature effects of different structural angles are measured, and found the bigger the structural angle is, the greater it* s splitting beam angles are influenced by temperature. To the same pieces of prism, the splitting beam angle from the positive incidence is influenced greater than that from negative incidence by temperature.In addition, constants expression of Sellmeier equation of quartz crystal are analytically calculated out, then the expression of the thermo-optical coefficients at different wavelength are got by curve-fitting means;The temperature effect of quartz Wollaston prism is studied, and found that the splitting beam angle of o light does not basically change when temperature is varied, while that of e light drop very fast, but comparing with calcite Wollaston prism of same structural angle, the influence by temperature is greatly smaller.