A Study of Multimode Interference Waveguide with Directional Coupler

• Main Authors: Chuan-Feng Yeh, 葉全峰
• Other Authors: Wei-Yu Li
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/81727204213271773352

碩士 === 中華技術學院 === 機電光工程研究所碩士班 === 93 === The subject of this thesis on the design and analysis of multimode interference (MMI) based optical passive devices for directional coupler. We propose a novel 1.3/1.55-μm wavelength demultiplexer on the LiNbO3 material system. A chirp grating is placed inside a MMI and periodically segmented waveguides in a directional coupler structure to shorten the device length and increase wavength tolerance. Simulation results show that a demultiplexer with an insertion loss of 0.156dB and 0.223dB can be obtained at 1.55- and 1.3-μm wavelengths, respectively. A new principle that can reduce the N-fold self-images interval of the MMI waveguide is presented. By placing some partial index-modulation regions in this multimode waveguide, a paired-interference mechanism and a symmetric-interference mechanism will exist simultaneously. The formulas in this thesis provide a simple design option to shorten the device length. The coupling characteristics have good tolerance on the device length and wavelength variation. Design of the device was carried out and it is showed that the device performance can be optimized by proper allocation of the periodically segmented waveguides.