Vanadium Yttrium Prism Temperature Characteristics

Polarizing prisms are the optical devices to generate polarized light.The birefringent polarizing prism is the most widely used in both the polarization light and the laser technology in modern times.Polarizing devices often play a mutual role with outfield during the process of employing.Temperature field can't be escaped by any polarizing devices.Temperature affects the performance of the instrument,equipment and devices.Much attention has been paid to this problem for a long time.Temperature effect research of the polarizing devices is very important to the development of optics project.The research has focused on the prism made of calcite crystal-a kind of negative crystal in the past years.YVO₄(positive crystal) polarization beam splitting prism,as a new-type polarizing devices,has also been widely used in both the polarization light and the laser technology in modern times.The dissertation puts emphasis on the YVO₄ crystal and Glan-type polarizing prisms made of the YVO₄ crystal.Thermal effects on both the material and the devices are also presented:The first chapter is the introduction part.It gives a summary of the basis of this topic,as well as work that has been done and the vital significance of the research.The second chapter deals with polarizing devices elementary theory.At first a brief introduction of crystal materials is given;Then some basic concepts of optics and ways to gain polarized light are presented;At last several kinds of daily polarizing prisms are introduced.The third chapter is about YVO₄ crystal temperature characteristic.Firstly,the material properties of the YVO₄ crystal are described and the notion of the chromatic dispersion are presented;And the expression of each constant in Sellmeier equation is analytically calculated out by testing the principal refractive index of the crystal.Then the expression of the thermo-optical coefficients at different wavelength are got by means of simple linear regression with least square method,by which we obtain the refractice indices corresponding in different wavelength under each temperature.Birefringence at the wavelength of 1064 nm can be got. Comparing its value with the value offered by the literature,we find Sellmeier equation has well expressed the relation of chromatic dispersion of YVO₄ crystal.Chapter Four is the kernel of this dissertation.In this chapter,we will discuss the effect that the temperature has on YVO₄ crystal,which is the original idea raised from this work.Elements made of YVO₄ crystal will change with temperature,and parameters of these elements like transmission ratio and extinction ratio will also change.According to the measuring principles of transmission ratio and the definition of extinction ratio,a testing system of the effects that the temperature has on the prisms was established.By means of this system,the temperature effect of the transmission ratio and the extinction ratio of the prism was tested.The result proves that, while the temperature is getting higher,the transmission ratio and the extinction ratio of the prism are getting lower.In order to analyze performances and parameters of Polarizing prisms overally,in Chapter Four,the elements which can affect the capacity of Polarizing prisms,as well as problems in the experiment are also discussed.The main task of this dissertation is:1) By testing the transmission ratio of YVO₄ crystal in the temperature control system,the transmission ratio curve at different temperature is got.Considering only the change of refractive index caused by temperature,the changing regulation of YVO₄ crystal's transmission ratio is theoretically calculated.The result is compared with the experiment result,which are coincident well.2) By testing the extinction ratio of YVO₄ crystal in the temperature control system,the extinction curve at different temperature is got.The result proves that the extinction ratio is getting lower while the temperature is rising.In order to explain these regulations,we have:3) Rearranged data according to our references:The main refractive indices of YVO₄ crystal at different temperature and wavelength,which provides references for calculating the theoretical value of the transmission ratio of YVO₄ crystal is presented;the refractive temperature indices of YVO₄ crystal at different temperature and wavelength can be calculated with the thermal refractive index coefficients.According to the references home and abroad,present studies of YVO₄ crystal as material are concentrated on crystal growth.And the studies of YVO₄ crystal prisms are concentrated on designing prisms and testing their performances.There's few articles about the subject on temperature characters of crystal polarizing prisms.Temperature affects mostly on the transmission ratio and the extinction ratio of YVO₄ crystal prisms.The study has practical values on analyzing performance indices as well as providing theoretical parameters in choosing and matching prisms in engineering experiments.