Design Bragg Reflectors Consisting of Quarter-Wave Stack and Impedance Matching Concept
Shymaa Hussain Salih

Dr. Adawiya J.Haidar , Dr. Kassim S.Kassim , Dr. Gailan H. Abdullah Abstract The control of the group delay and group delay dispersion in the design of chirped mirror is difficult. To reduce this difficult it is important to adopt what is so called impedance matching design. This paper presents a design of quart wave mirror which includes the impedance matching. The design is divided into two stages. In the first stage a quarter waves stack to provide high reflectivity of over a bandwidth of the design and within certain limits is considered. The control on average group delay depends upon wavelengths that are function of penetration depth. However, the group delay as a function of wavelength shows periodic variations due to the impedance mismatch between the ambient medium and the mirror surface and its layers. In the second stage of the design tapered Bragg stack over a wavelength range (600-1100nm) is adopted as a single chirp.