The Effect Of Dispersion Based On Optical Rotation Of Quartz Crystal Optical Rotation Optical Filter

The optical filter based on the optical rotatory dispersion effect is an important optical tuning device,which is composed of n optical rotators[rotation angles,ρ₁,ρ₂,ρ₃,…,ρ_n]and n+1 polarizers[azimuth,P₁,P₂,P₃,…,P_n+1].The ratios between the rotation angles are assumed to be 1:2:4:8:……2^n-1and the ratios between the relative azimuths are the same as those of the rotation angles,i.e.(P₂-P₃):(P₃-P₂):(P₄-P₃):…,(P_n+1-P_n)=ρ₁:ρ₂:ρ₃:…:ρ_n.The polarizers and rotators are arranged in series along a light beam's axis to form n single stages,each containing one polarization rotator separated by polarizers.In such a way,the exit polarizer of one stage serves as the entrance polarizer of the following stage.So the filter was tuned when the intermediate and exit polarizers were rotated.This filter has some merits such as low cost,easiness to construct,high transmission and wide range of use.In this paper,the quartz optical filter based on the optical rotatory dispersion effect was constructed by quartzs and polarizers,and the filter principle was systematically investigated after the existing domestic and foreign work about optical filter was investigated in detail.Using Muller matrix and Stokes parameter,theoretical calculation formulas for characteristic parameters were deduced from the optical quartz filter's transmission equation based on the rotatory dispersion effect.The factors which have effect on the single-stage and multiple-stage filter's filter characteristics were theoretically and experimentally analyzed.So this work could be very useful for designing and constructing a high performance optical quartz filter.The full text mainly includes four chapters given as follows.In the first chapter,we introduce the development and present research of the optical filter. The work of this paper is also introduced.In the second chapter,a few fundamental theories about the optical filter are introduced. Firstly,some characteristic parameters which are used to describe the filter characteristics are simply discussed.Then the classification of the optical filter and their filter principles of them are introduced in detail.The third and fourth chapters are the most important parts in this paper.In the third chapter, the filter principle of the optical quartz filter based on the rotatory dispersion effect is investigated.Firstly,the optical rotatory dispersion effect of the quartz was analyzed and the transmission equations of single-stage and multi-stage filter were deduced.Then the calculated transmission curves of filters are fitted by the deduced equations.According to the fitting results, the main peak's wavelength and free spectral range of the multi-stage filter is determined by the thinnest quartz;the full width at half maximum is determined by the thickest one.Next,the theoretical calculation formulas for characteristic parameters of the single-stage and multi-stage filter were deduced from the quartz optical filter's transmission equation based on the rotatory dispersion effect.The formulas show that the characteristic parameters have direct relationships with the stage of the filter and the thinnest quartz.So the values of the characteristic parameters of n-stage filter can be calculated with thinnest quartz's thickness d₁ and then the filter effect can be described.The qualified filter can also be designed.In order to get the monochromatic frequency-doubled lasers,an optical quartz filter for selecting the frequency-doubled laser based on the optical rotatory dispersion effect was designed.The operating principle was analyzed and the results indicated that the second-harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of(2n+1)π/2(n=0,1,2,3,...)between the second-harmonic laser of a frequency-doubled laser and the fundamental laser.The effect of the quartz's thickness error on the filter effect was also discussed and the results showed that the filter effect is little and it is a perfect filter for the frequency-doubled laser.In the fourth chapter,the spectral transmission of the optical quartz filter was measured by a spectrophotometer(UV-3101PC).Firstly,the quartz,polarizer and optical cement's spectral transmissions were measured firstly.Then the single-stage and multi-stage filter was constructed with quartz optical rotators and polarizers according with the arrangements,and its spectral transmission of them was measured.The measured transmission curve is in accord with the theory,and the experimental results of characteristic accord with the one that deduced from the theoretical equations.These results indicate that the calculated curves and the equation are correct.By analyzing the measured transmission profiles,we can draw the conclusion that the rational value of the thicknesses to the minimum thickness among the quartzs in the filter plays an important role in the filter's effect.Finally,the optical quartz filters for selecting the frequency-doubled laser(532nm and 559nm)were constructed and the spectra of the output laser were measured.The experimental results are in good agreement with the theoretical analysis.In addition,the structure and operating principle of spectrometer UV-3101PC used in the experiment was introduced,and based on the optical rotatory dispersion effect of the quartz,a spectral method for determining the thickness of quartz plate along the crystal axis is presented. The method can improve the measurement accuracy of the thickness and do no damage to the quartz's surface.The error in the experiment is also analyzed,and it is found that the measuring accuracy will be improved by some methods which can guarantee the reliability of the test results.