Low-threshold stimulated emission at 249 nm and 256 nm from AlGaN-based multiple-quantum-well lasers grown on sapphire substrates

Xiao Hang Li, Theeradetch Detchprohm, Tsung Ting Kao, Md Mahbub Satter, Shyh Chiang Shen, P. Douglas Yoder, Russell D. Dupuis^*, Shuo Wang, Yong O. Wei, Hongen Xie, Alec M. Fischer, Fernando A. Ponce, Tim Wernicke, Christoph Reich, Martin Martens, Michael Kneissl