Determination of Reactive RF-Sputtering Parameters for Fabrication of SiOx Films With Specified Refractive Index, for Highly Reflective SiOx Distributed Bragg Reflector

• Main Authors: Elnaz Afsharipour, Byoungyoul Park, Cyrus Shafai
• Format: Article
• Language: English
• Published: IEEE 2017-01-01
• Series: IEEE Photonics Journal
• Subjects: Distributed Bragg reflector (DBR); genetic algorithm; optimization; photonic crystals; photonic materials; refractive index of SiO<sub xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">x</sub>.
• Online Access: https://ieeexplore.ieee.org/document/7809096/

Fabricating materials with specific refractive indices, which do not naturally exist in the nature, has always been an issue. This paper presents a method for fabricating SiO_x films with specified refractive index. It is well known that the refractive index of reactively sputtered SiO_x films depends on its deposition conditions; in this paper, this fact was employed to fabricate films with arbitrary refractive indices. A statistical study and a Genetic Algorithm are implemented that can determine the deposition conditions (including oxygen partial flow and pressure) for fabricating a film with an arbitrary refractive index in the range of 1.4-4.2. The method was experimentally shown to correctly determine the deposition conditions. The functionality of using the proposed method in fabricating optical components was further evaluated by fabricating a distributed Bragg reflector (DBR) consisting of 4.5 pairs, whose refractive indices of the layers were determined by the proposed method. The DBR featured a high 95% reflection in a bandwidth of more than 270 nm, which can be categorized as a high-quality DBR. The advance of the proposed method is that the films are made from a single target source without making any physical changes in the target or substrate positions.