报告题目：Advanced Quantum Cascade Lasers: Design and broadband tuning
报告人：Quankui Yang（Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg, Germany）
Quantum cascade (QC) lasers are based on unipolar carriers making intersubband transitions within e.g. the conduction band. In this talk, we will discuss the design and molecular beam epitaxial growth issues of broadly tunable hetero-cascading QC lasers. Attention was paid on the goal that all the individual active regions should operate under identical electric field, and similar threshold current density should be achieved simultaneously for all the active region sections. The optical confinement factors for each active region were adjusted so that the total gain spectrum should have a flat top, to enable a large tuning range. A narrow-linewidth emission covers a frequency range of 300 cm-1 (1050 cm-1 to 1350 cm-1) has been achieved for a single laser chip. For external-cavity QC lasers fabricated in our institute, narrow- linewidth emission has been achieved to cover the wavelength range from 4.2 µm to 10.5 µm without any gap.
Quankui Yang received the Bachelor of Sciences degree from Wuhan University, Wuhan, China, in 1995, and the Ph. D. degree in Solid-State Electronics from the Chinese Academy of Sciences, Shanghai, China, in 2000, both with honors. After that he joined the Fraunhofer Institute for Applied Solid-State Physics (IAF), Freiburg, Germany in 2000, as a postdoc, and holds a permanent position as a senior scientist at the Fraunhofer IAF since 2002. His work mainly focuses on the development and application of infrared semiconductor lasers, in particular quantum cascade lasers. His interests also include other semiconductor devices such as infrared detectors, heterojunction bipolar transistors, and backward diodes. Dr. Yang is a co-inventor of 4 patents, has co-authored 85 peer-reviewed journal papers, more than 90 presentations in international academic conferences, and contributed to an edition of Landolt–Börnstein dedicated to quantum cascade lasers.