The image on our cover this month highlights another quest for speed. In the field of ultrafast lasers, making femtosecond light pulses is now fairly routine—in fact, several turnkey ultrafast systems are commercially available. Now, however, the ante has been raised by an international collaboration of researchers who have produced pulses in the attosecond (10-18 s) range. Their 650-attosecond soft x-ray pulses are reportedly the fastest measured to date (see p. 17).
SiGe quantum-well device lases in the terahertz region
An assemblage of European and American researchers is working toward making a silicon germanium (SiGe) laser that emits terahertz radiation. The group includes scientists from the Institute of Radioengineering and Electronics of RAS (Moscow, Russia), the Royal Institute of Technology (Kista, Sweden), the University of California (Los Angeles, CA), Lund University (Lund, Sweden), and the A. F. Ioffe Physico-Technical Institute of RAS (St. Petersburg, Russia). Acceptor-doped SiGe has good thermal properties, low absorption in the terahertz range, and low cost, and can be integrated with Si-based electronics.