Binary Birefringent Crystal Depolarization Of The Study

Depolarization is opposite to polarization concerns with transforming light states of polarization. Polarization and polarizers are more concerned by human beings than depolarization and the depolarizer. Because most of the detectors have sensitivity to polarization, it's necessary to add a depolarizer in the front of the detector to erase the dependence of sensitivity. The depolarizers are widely used in many photoelectric measuring instruments, such as astronomical instruments, laser processing, laser medicines, optical fiber communication and so on.There are mainly two methods to achieve depolarization. Letting polarized light passes through the scattering medium or birefringent material of gradient phasic difference are both of them. The transmissivity of light intensity is so low when polarized light passes through the scattering depolarizer that the depolarizers are usually made by birefringent materials in fact.Study of depolarization of crystal focused on simple crystal and Lyot depolarizer from the national and international references. But study of depolarization of dual birefringent crystals in a common situation hasn't been discussed .So there are some values studying it .This thesis includes four chapters. The history and present research of depolarization and the depolarizer are discussed in the first chapter.In chapter two, the description methods of polarized light and depolarizer are discussed. The Stokes vector of different polarized light and the Mueller matrix of different polarization device are given;two definitions of degree of polarization and the introduction of degree of depolarization are also given;the coherent matrix is also introduced;several methods of depolarization are given;the principle of the common polychromatic depolarizer and monochromatic depolarizer are analyzed in brief.Study of depolarization of dual birefringent crystals is introduced in chapterthree. The principle of wedge depolarizer is introduced;the depolarization mechanism of quartz rotatory depolarizer is analyzed. Depolarization of dual-birefringent crystals is introduced as follows: Starting from calculous and optics matrix, the performances of white light by a dualistic birefringent crystal with several different optical axis angles and thicknesses are discussed, some conclusions can be drawn: (DThe depolarization of emerging light is relative to the thickness of the dualistic birefringent crystal, the optical axis angles and polarization direction of the incident light;?Different optical axis has an indirect effect to the polarization of emerging light;the polarization of emerging light might differ with same axis angle. ?The thickness of the crystal has an important effect on the degree of polarization. In order to make sure of enough retard of crystal and enough retard phase, the thickness of crystal should be made to achieve it. One of parameters which affect the thickness is the thickness parameter(X), we can calculate the thickness of crystal according to the following formula: t = Xhc/ln2 AnkT ,or rather, we can calculate the parameter X in relative to the degree of polarization. ?The ratio of the thickness of two crystals has an effect on the degree of the polarization. In order to receive an ideal polarization, the retard phase of thickness should be different and the ratio should be an integral. At last in this chapter the depolarization performance of a combination of dualistic wave plates is discussed: a polarizer which made by the combination and the rotating frequency ratio of the 1/4 plate and the 1/2 plate is 1:2, is discussed;The effect of depolarization is not ideal particular to the linear polarized light when light goes through the combination of 1/4 or 1/2 plates.Experiments are given to proof the theory of the dualistic birefringent crystal in chapter five. The experiments data coincides with the theoretical data in the range of the experimental errors.The original innovations of this thesis contain :1. Depolarization performances of white light of a dualistic birefringent crystal is discussed with a theoretical way. The results of theory are also validated with anexperiment. These conclusions can give theoretic analysis and reference to design the depolarizers and to apply them.2. The depolarization performance of a combination of dualistic wave plates is discussed, a theoretical analysis is also given to the combination of 1/2 plate and 1/4 plate. The results of theory are validated with an experiment. It's a development of this type.