Study Of The Polarization Property Of Chiral Multi-helix Grating

Chiral fiber grating was first proposed by Kopp etc. Chiral fiber grating not only havewavelength selection characteristics of traditional gratings but also havepolarization-sensitive characteristic which traditional gratings did not have. It can be used asfilter, circular polarizer, sensor and many other aspects. What is more, it showed greatadvantages in these applications. For example, when used as circular polarization, itsworking range is much larger than the traditional circular polarizer; furthermore, comparedwithraditional circular polarizer, the volume of chiral fiber grating circular polarizer is muchsmaller than the traditional one, so it is more convenient for integrating. When used astemperature sensor, it can measure wide range of high temperature at high accuracy.In order to learn the polarization property of chiral fiber grating more comprehensively,the thesis mainly study polarization sensitivity of the chiral fiber grating through theoryanalysis and simulation. Firstly, the polarization insensitivity of single-helix chiral fibergrating and polarization sensitivity of the double-helix was explained using the coupledmode theory. Secondly, the all wave conversion length of long period chiral double-helix iscomputed. Followed by that, the modes of intermediate period chiral fiber grating wereanalyzed. Finally, the polarization property of single-helix, double-helix, triple-helix andquadruple-helix were systematically studied. The results show that the single-helix andfour-helix are polarization insensitive while double-helix and triple-helix are polarizationsensitive. What is more, the polarization sensitivity of the double-helix is superior to thetriple-helix. Finally, in order to summarize the pattern of polarization sensitivity, we tookdouble-helix for example and discussed the various parameters of the double-helix, thechange of parameter mainly affects the wavelength and depth of dip which is caused bypolarization sensitivity.