Study For The Antireflection Of The Subwavelength Diffractive Optics Elements

This paper is divided into two sections. The first section includes the theoretical and numerical analysis for diffractive optics elements and the second one gives the results of the fabrication experiments of diffractive optics elements.In the first section, we analyzed the antireflection of the diffraction optics elements. Binary optics processing methods may be applied to a glass or silicon substrate to generate an array of small columns in order to enhance transmission. We employ the rigorous vector coupled-wave theory to analyze the electromagnetic diffraction nature of two-dimensional columned grid gratings. By computer simulation and calculation, the relation between the reflectivity and the structure parameters of such gratings are presented. These results show that a glass grating can achieve antireflection over almost the whole visible light waveband for unpolarized light, while a silicon grating with a columned grid substrate also can achieve low reflectance over as a broad field of view as a tapered silicon grating structure can, but it can be fabricated more simply.In this section, we also designed 2D subwavelength multilevel (2-, 4-, 8-, etc. level) columned stairstep grating with coned spatial profile to reduce reflection. The structure is shown to achieve extremely low reflectance over a wide field of view and a wide light wave band.In the second section, we analyzed the etching surface. It is very importance to analyze the evolution of microscopic surface features, which impact on the etching surface shape in solid etching process. Much theoretical and experimental study point out that the different etching surface shapes by the plasma beam with same energy will be different. In the fabrication of diffractive optics elements and semiconductor, it is demonstrated that an initial edger can expand into smooth curves and the surface motion in different local place is not identical. Generally, the etching rate for different local surface is dependent of the local slope of the surface. In this paper, we call this phenomena quasi-direction effect. To reduce the difficulty, we use a mathematical model for the surface shape analysis in this paper. We give some useful analyses and the computer simulations for the ion etching process. Compared with the atomic force microscope (AFM) scanning photograph of the etching surface, the theoretical results prove that these simulation analyses assure the precision required by this problem, so these mathematical models are reasonable and correct. The analysis method in this paper is useful to analyze etching process, and it can also afford some valuable reference to etching technology.