Análise de guias de onda ópticos segmentados com sequência quase periódica

Abstract

Waveguides with high contrast of refractive indexes between the core and the cladding, usually present considerable scattering losses in the imperfections of the core walls. A possible solution to solve this problem can be the stratification of the core, through the process of segmentation using materials with different refractive indexes. In this work, the vectorial beam propagation method (VBPM) is applied in the analysis of segmented waveguides with quasi-periodic sequences. The structure has intercalated refractive indices along the propagation direction and to obtain a quasi-periodic distribution along the direction of propagation, the Fibonacci sequence was used. In this case, the non-periodicity of the sequence was applied in order to reduce scattering losses caused by imperfections in the walls of the guiding region. Two models of dielectric waveguides were studied. The first to be analyzed was a rectangular waveguide of pure silicon immersed in a silicon dioxide substrate. Then, it was analysed a rectangular waveguide of pure silicon with a silicon dioxide substrate, and an overlay of a photoresist, known as SU-8, was deposited on this basis. The procedure for analysis is based on the propagation of the transverse modes of the structure along the guiding region, considering the power variation and the dispersion of the sequenced guide. The results were obtained using a computational platform with code written in FORTRAN 2008 in conjunction with the PYTHON programming language. The results show a good response in the distribution of modes, which results in less power loss due to imperfections in the sidewalls of the guide core. According to the results, it was found that the use of the proposed waveguide presents lower insertion losses, decreases the contrast between the refractive indexes of the core and the cladding and exhibits a linear dispersion.