A Study of the Cross Section of Distributed Bragg Reflector on Lithium Niobate Waveguide

• Main Authors: Yi-Ting Kuo, 郭宜婷
• Other Authors: Way-Seen Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/56698661972605559918

碩士 === 國立臺灣大學 === 光電工程學研究所 === 88 === Distributed Bragg reflector (DBR) can provide high reflectivity and narrow bandwidth when it is applied as the cavity mirror of an erbium-doped LiNbO3 waveguide laser. Additionally, DBR can be integrated with other integrated optical devices. However, the traditional erbium-doped LiNbO3 waveguide laser was produced by etching the groove directly on it, such that the reflectivity is limited. The reflectivity can be improved if the Si-on-LiNbO3 structure is used, and the groove is produced on Si-layer. In this thesis, this structure is analyzed by the cuopled-mode theory. The insertion loss caused by mode profile mismatch and the trapezoid shape of groove due to the processing are both considered. The simulation results show that the reflectivity is more sensitive to the cross section of the groove than to the slope of the hypotenuse of trapezoid shape grating. Furthermore, the reflection spectrum has more narrow bandwidth and suffer the maximum reflectivity reduced slightly as the slope is smaller. Thus, the perfect rectangular shape of the grating is not necessary. Finally, the aperiodic DBR structure are used to improve the bandwidth and side lobe.