Number 65 (Story #2), January 24, 1992 by Phillip F. Schewe and Ben Stein EXPLOITING MECHANICAL STRAIN EFFECTS IN SEMICONDUCTORS has allowed researchers to achieve some of the latest advances in laser design. In the newest models, light is released from ultra-thin, nanometer-scale junctions known as "quantum wells." Compared to the thicker junctions made in the past, quantum wells can better tolerate the surface strain which arises when the atoms in the well layer have different atomic spacings from those in the surrounding p- and n-semiconductor layers. As a result, scientists can vary materials in the junctions to a greater degree than ever before, bringing about a much wider variety of energies in semiconductor lasers. Straining techniques in quantum wells led to the first semiconductor lasers in the green range (New Scientist, 11 Jan.1992). In addition, the fastest laser yet, a gallium-arsenide-based laser which turns on and off 28 billion times a second, appears to have resulted from straining effects on the Ga-As lattice produced by a Ga-In-As quantum well. (Science News, 11 Jan.1992)