报告 题 目: High Speed VCSELs and their Applications
报 告 人 ：Werner Hofmann教授
报 告 时 间：2018年3月28日(星期三) 10:30
报 告 地 点：研发大厦第二会议室
报 告 内 容：With the increasing bandwidth demand of optical interconnects, directly modulated VCSELs with ultimate speed ratings are needed. For serial 100 Gbps solutions today´s VCSELs have to increase their high speed performance. Here we report about our next generation devices, an optimized version of our very successful high-speed, temperature-stable 980 nm VCSELs featuring a very short half-lambda cavity and a binary bottom-mirror with 32 pairs, levels were further optimized in order to minimize internal loss. Like previously, parasitics are controlled by two oxide apertures and highly conducting current-spreading layers. InGaAs MQW active layers with with strain compensated GaAsP barriers were utilized for high differential gain. The 22-pair Al12Ga88As/Al90Ga10As top-mirror was replaced by a 18-pair GaAs/Al90Ga10As mirror for lower photon lifetime, better confinement and better heat extraction. The epi-structure was grown by IQE Europe. The VCSELs showed modulation bandwidth around and exceeding 30 GHz. The common set of figures of merit is expanded consistently to explain dynamic properties caused by carrier fluctuations. This new model allows the consistent extraction of figures of merit and can explain mode-dependent dynamics. Additionally, we would like to point out cultural differences between Germany and China, especially focusing on the education system.
专 家 介 绍：
Werner Hofmann is professor for Nanophotonic Devices, and CTO of the Center of Nanophotonics at the Technical University of Berlin, Germany. He received his Dipl-Ing degree in 2003 and the Dr.-Ing. degree in 2009 both from the Technical University of Munich, Germany. From 2003 to 2008, he was with the the group of Prof. Amann at the Walter Schottky Institute, where he was engaged in research on long-wavelength vertical-cavity surface-emitting lasers (VCSELs). Subsequently, he joined Prof. Chang-Hasnain´s Group, University of California at Berkeley, where he worked on the incorporation of high-contrast gratings into VCSEL devices. In 2010, he joined the Technical University of Berlin as principal scientist in the group of Prof. Bimberg. Since 2013 Prof. Hofmann is leading his own group focusing on ultra-high-speed nanophotonic devices. Since 2014 he is also with the Xiamen University, P. R. China as guest professor. Prof. Hofmann authored over 100 papers cited over 500 times and has presented over 10 invited talks and tutorials on international conferences. He is a member of the Association of the German Engineers (VDI), the German Association of University Professors (DHV) and the IEEE Photonics Society. Werner Hofmann also serves on conference organizing and program committees like the SPIE Photonics Asia.