Design And Fabrication Of Diffractive Elements For Terahertz And Infrared Lightwave

With the rapid development of the research in terahertz and infrared frequency region,the applications of terahertz and infrared lightwave technology have being extended year byyear, and then the exploitation of the diffractive elements has became an importantstudying field. In this dissertation, a special designing software is developed for acquiringdiffractive elements employed in terahertz and infrared region, respectively, according to thediffractive theory. Several elements are fabricated by standard semiconductor technologicalprocess. Infrared diffractive elements are mainly used to form complex wavefront fields andthe terahertz elements are used to focus incident terahertz beams and generate severalparticular patterns, respectively.The software is programmed and run in the Matlab. The software is composed of fourmodules including the module of the visible-interface, the module of theset-default-parameter, the module of the calculating-phase, and the module of the creating-cif-file. The module of the visible-interface can be used to create the window, the menus,the display areas, and the buttons of the software. The module of the set-default-parameterwill be assigned needed parameters values when the module is called. The module of thecalculating-phase can be used to simulate the diffractive process according to the commonRayleigh-Sommerfeld diffractive theory or angular spectrum diffractive theory, and then thephase distribution of elements can be calculated by Gerchberg-Saxton (GS) Algorithm. Themodule of the creating-cif-file can be employed to create cif files according to the practicalprocess.The developed software is also used to design several diffractive elemnts. According tothe practical requirements, the software is further improved and extended, such asrobotization-calculation, generation pattern module, the module of reading-writing-patternfile, testing module for measurement imaging efficiency. An new method or so calledsubarea calculating is proposed to decrease the data in acting software, to reduce the file, andto make the technological process more easily.Several devices are fabricated according to the standard semiconductor technology,which mainly includes making photomask, growthing protective film layer, photolithography and etching. In this dissertation, the key technological process in the wet etching and dryetching are discussed, and the different requests in both etching operations above are alsoanalyzed. The layout “cif” file is explained explicitly through combining the restrictionconditions in acting technological process.Infrared wavefront elements for constructing several typical wavefront fields have beensimulated and designed, and then the technological processes for fabrication devicementioned above already arranged. The terahertz diffractive elements for generation severalpatterns have been fabricated and measured. The experiments show that the devices alreadyreach the target expected.