A Simple Analytic Method for Design of Optical Circular Grating Fillets with Phase-Shifting Region

Circular Bragg gratings(CBGs) canbe incorporated in most of the semiconductor laser devices because of the frequemcyselective property applicable as an optical narrowband-pass filter in DWDM optical communications. In this paper, the optical filtering characteristics of CBGs are evaluated by a novel and simple analytic modal transmission-line theory(MTLT), which is based on Floquet-Babinet's principle. The numerical results reveal that this method offers a simple and convenient algorithm to analyze the filtering characteristics of CBGs as well as is extended conveniently to evaluate the guiding problems of circular multi-layered periodic structures.