Abstract : The Terahertz gap, lying roughly between 300 GHz (0.3 THz) and 30 THz in the electromagnetic spectrum, exists because the frequencies generated by semiconductor based transistors and lasers do not overlap. The generation of coherent terahertz radiation has traditionally involved either extending electronic techniques to higher frequencies, or extending photonic sources to longer wavelengths. In both cases, the efficiency drops rapidly as the frequency approaches the terahertz region.

It was recently reported that the operation of the quantum cascade lasers based on GaAs/AlGaAs could be extended from the mid-infrared range to terahertz. In this talk, I will first review the basic principles of operation of the quantum cascade lasers. Next, a few key issues related to the THz generation will be addressed. The design, fabrication and electrical, and the optical characterizations of our terahertz quantum cascade lasers will then be presented. Recent experimental results from Dr. Ban’s group, such as doping effects, in-situ active-region temperature measurement, and thermal dynamics of THz quantum cascade lasers will follow.

Biography : Dr. Ban received his B.S. and M.S. degrees, both in physics, from the University of Science and Technology of China, Hefei, China, in 1993 and 1995, respectively, and his Ph.D. degree in Electrical and Computer Engineering from the University of Toronto in 2003. During 2001-2002, Dr. Ban was a visiting scientist at the Nortel Networks Optical Components, Ottawa, Ontario. After being with the Institute for Microstructural Sciences of the National Research Council for three years, in Nov.2005, Dr. Ban joined the Department of Electrical and Computer Engineering at the University of Waterloo. He is currently on sabbatical leave and is visiting the Research Laboratory of Electronics at MIT in Boston. Dr. Ban’s research interests include quantum optoelectronic devices, scanning probe microscopy, nanofabrication, infrared LEDs, photodetectors and up-converters, fiber Bragg grating sensors, and Terahertz quantum cascade lasers. He has authored/co-authored over 80 publications. Dr. Ban is the recipient of the Distinguished Performance Award from the Faculty of Engineering in 2008, Early Research Award and CFI Leader’s Opportunity Award in 2007.

Live webcast : http://vbxevents.powerstream.net/003/02484/Mar5/index.htm

Presentation Slides : http://www.dss.uwaterloo.ca/presentations_files/2009_Dayan_Ban.ppt