Study On Diffraction Characteristics Of Several Dielectric Gratings

With the development of microfabrication, diffraction gratings become more and more important in modern science. This thesis mainly deals with the direct problems in the application of the diffraction gratings, that is, analyzing gratings' diffraction behaviors according to their geometry parameters, physical parameters and incident field information. In other words, we study diffraction gratings with the rigorous vector coupled-wave theory and scalar diffraction theory. This article mainly includes following aspects:1. Summarizing basic knowledge of diffraction gratings.We summed up some basic knowledge of diffraction gratings in this thesis, which includes diffraction gratings classification, basic nature (namely chromatic dispersion, splitting beams, polarization and phase match), Rayleigh expansions, reciprocity theorem, equivalent regular, phase shift theorem, generalized diffraction grating equation and scalar diffraction efficiency. These theories are very helpful to design and application of diffraction gratings.2. Researching on the rigorous vector coupled-wave theory and designing software DiffGrating1.0.The rigorous vector coupled-wave theory is one of the diffraction vector algorithms for gratings. We deduced the process of the rigorous vector coupled-wave theory solving diffraction efficiencies of rectangular gratings and free profilegratings, moreover, we changed the matrix form of the final result to calculate expediently and used enhanced transmittance matrix approach to improve its numeric stability. Then we designed diffraction gratings' efficiencies computation software DiffGratingl.O.The software, which need not to be installed, and can be run directly in the Windows operating system, is a green software. Also,with its friendly interface and powerful function, it not only calculates diffraction efficiency of sine gratings, symmetrical triangle gratings, symmetrical trapezoidal gratings, saw-tooth gratings and free profile gratings based on the input parameters, but also draws relational curves of diffraction efficiencies and incidence angle, wavelength and period for above diffraction gratings. As a result of its good computation pertinence, the operating speed is high.We used DiffGratingl.O and above theories to study the influence of gratings' geometry parameters and incident field parameters upon diffraction gratings' efficiencies, at the same time, we studied the relation between harmonics numbers and astringency of diffraction efficiency. As we used uniform thickness multilayer approximate method to solve free profile gratings, we find that it is very necessary to study the relation between thin layer numbers and diffraction efficiency astringency. In addition, we confirmed reciprocity theorem and equivalent regular.3. Study on color separation gratings (CSG), beam sampling gratings (BSG) and polarization gratings (PG).CSG and BSG are important subassembly of the ICF terminal optics elements; we studied their diffraction characteristics, fabrication processes, alignment error, depth error, duty cycle error and incidence error, etc. In addition, we regarded sine gratings and rectangular gratings with uniformity period as BSG's analog and studied their some characteristics. As a result, it indicates sine gratings and rectangular gratings with uniformity period can well approximate to BSG except that sine gratings don't possess BSG's congregate function. PG is one kind of new polarization optics elements, which is studied widely overseas. However, we have not seen domestic concerned reports, although a lot of research results have beenpublished in foreign periodical. We studied polarization characteristic and diffraction characteristics of PG, and discussed PG which was used as the optical switch and the beam separator. Then we introduced the method that deducing the grating function according to the grating vector, which has important referenced value to polarization gratings' design and manufacture.