Quartz Crystal Optical + Birefringent Composite Optical Filter Design And Characteristics Of The Study

The quartz crystal is a kind of common material for making optical filters. It has highdamage threshold, easy processing, easy obtaining and its deliquescence is unlikely. At the sametime, it also has birefringence and optical activity. Investigation at home and abroad show thatfilters made of this crystal can be divided into two main categories: birefringent filter and opticalrotation filter. After analysis of transmission spectrum of both kind of filters, it is found that theyall have a continuous range of spectrum, which allow multiple non-target peaks besides maintransmission peak. In view of this shortcoming，we make use of optical activity of the crystal toeliminate or decrease non-target transmission peaks. Thus we can achieve light-wave with asingle wavelength in a wide spectrum range.The paper is divided into five chapters:The first chapter is introduction. It is mainly about the development and status of the filterat home and abroad and the work to be done in the paper accordingly.The second chapter introduces performance parameters and classification of filters. Thestandard and angle of measuring filter performance is given, and several type of filters are brieflyintroduced based on their different filtering theories.In the third chapter the basic theory of the two optical filters by quartz crystal, which is alsothe basis of the design in this paper, is given. It includes basic design idea of the standardbirefringent filter and the rotation optical filter as well as their filtering effect. What’s more,dispersion curve of the refractive index is gotten by the modified Sellmeier equation.Chapter four is the core content of this paper. The innovations lie in: In view of theshortcoming that they all have a continuous range of spectrum, which allow multiple non-targetpeaks besides main transmission peak，a compound optical filter combining optical activity ofquartz crystal with its birefringence is designed. The principle of this filter is analyzed detailedly,and its transmittance formula is also derived detailedly. It is found that the filter can reducenon-target peaks indeedly, and half width of passband decrease gradually simultaneously withthe increase of the series by observing the theoretical transmission curve of the filter. Accordingto the analysis, the effect of the birefringence device is mainly to compress bandwidth while theeffect of the rotator is to reduce non-target peaks in this compound filter. Thickness error of thefilter is theoretically analyzed by transmission spectrum. To get the filtering effect, redesign ofthe filter is done by half-width of passband finally.Chapter five is the part of experiment. The design of the sample is stated and test is done byTsushima UV-3101PC spectrophotometer. By comparison of the experimental transmissioncurve with the theoretical transmission curve, it is known that the filter can achieve the purpose of the design, ie, the achievement that a single wavelength wave is transmitted in a widewavelength range. Accordingly the feasibility of our design and the correctness of the formuladerivation are verified.