Fabrication and characteristics of rugate filters deposited by the TSH reactive sputtering method

Abstract

Theoretical investigations on rugate filters have recently received much attention. For the most efficient use of the rugate filters, the deposition processes such as EB coevaporation, reactive ion beam assisted deposition and chemical vapor deposition methods, have been investigated as the most importance to achieve our objective. However, since periodic rugate filters manufactured in these manners require sophisticated and precise control of the process, they cannot sufficiently offer either the required stable deposition rate, wide variation of refractive index, or a particularly long-time constant deposition process. In this experiment, the two-stage high-rate reactive sputtering method, called TSH reactive sputtering, is used to fabricate such rugate filters. Their spectral performance, elemental composition ratio, and cross-section morphology have been investigated.