Novel grating design approach by radiation modes coupling in nonlinear optical waveguides

作     者：Massaro, A. Cingolani, R. De Vittorio, M. Passaseo, A. 

作者机构：Univ Salento Distretto Tecnol ISUFI INFM CNRNatl Nanotechnol Lab I-73100 Lecce Italy IMM CNR Sez Lecce I-73100 Lecce Italy 

出 版 物：《OPTICS EXPRESS》 (Opt. Express)

年 卷 期：2009年第17卷第9期

页      面：6982-6995页

核心收录：

学科分类：070207[理学-光学] 07[理学] 08[工学] 0803[工学-光学工程] 0702[理学-物理学] 

主　　题：.tailored guiding conversion efficiency guided modes Enhance GaAs/AlGaAs optical waveguides coupled mode design approach radiation modes substrate region core/substrate inside the waveguide 

摘      要：In integrated optics the radiation modes represent a negative aspect regarding the propagation of guided modes. They characterize the losses of the substrate region but can contribute to enhance the guided modes by considering the coupling through properly designed gratings arranged at the core/substrate interface. By tailored gratings, the radiation modes become propagating modes and increase the guided power inside the waveguide guiding region. This enhancement is useful especially in low intensity processes such as second harmonic. chi((2)) conversion process. For this purpose, we analyze accurately the radiation modes contribution in chi((2)) GaAs/AlGaAs nonlinear waveguide where second harmonic signal is characterized by a low power intensity. This analysis considers a new design approach of multiple grating which enhances a fundamental guided mode at lambda(FU) = 1.55 mu m and a codirectional second harmonic guided mode at lambda(SH) =0.775 mu m. In particular we analyze the second harmonic conversion efficiency by studying the coupling effect of three gratings. The combined effects of the gratings provide an efficient second harmonic field conversion. Design considerations, based on the coupled mode equations analysis, are theoretically discussed. A good agreement between analytical and numerical results is observed. (C) 2009 Optical Society of America