Monolithic Integration of Optical Spot-Size Converter and High-Speed Electroabsorption Modulator using Laterally Tapered Undercut Waveguide

• Main Authors: Fang-Zheng Lin, 林方正
• Other Authors: Yi-Jen Chiu
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/27mg2z

博士 === 國立中山大學 === 光電工程學系研究所 === 97 === This thesis proposes a novel structure to realize the monolithic integra-tion of optical spot-size converter (SSC) and high-speed electroabsorption modulator (EAM). The SSC is based on a scheme of coupled asymmetric waveguide fabricated by tapered undercut waveguide. Using a selectively undercut-etching-active-region (UEAR), the laterally tapered undercut ac-tive waveguide (LTUAWG) can be processed from a wide tapered ridge waveguide using in situ control to avoid submicron photolithography as well as complex processing, such as selective area growth, selective area etching and re-growth. By monolithically integrating EAM and SSC, the EAM waveguide width can be beneficial from scaling down the waveguide size for enhancing the EAM bandwidth, while the optical coupling loss from single mode fiber can still be kept low. In this finished SSC-integrated EAM, a 1-dB misalignment tolerance of ±2.9μm (horizontal) and ±2.2 μm (vertical) is obtained from SSC side, which is better than the results, ±1.9μm (horizontal) and ±1.6μm (vertical), from EAM side. The measured far-field angles for SSC and EAM are 6.0 (horizontal) ∗ 9.3 (vertical) and 11 (horizontal) ∗ 20 (vertical) respectively. As low as mode transfer loss of -1.6 dB is obtained in such SSC. All the simulation results are quite fitted with the experiment results, realizing the function of SSC by LTUAWG. The fabricated EAM waveguide width is 2.5 μm, leading to over 40 GHz of -3-dB electrical-to-optical (EO) response. The high efficient SSC integrated with high-speed EAM suggests that the LTUAWG technique can have potential for applications in high-speed optoelectronic fields.