Switching to a laser record.A year ago, Lester F. Eastman and his collaborators at Cornell University Cornell University, mainly at Ithaca, N.Y.; with land-grant, state, and private support; coeducational; chartered 1865, opened 1868. It was named for Ezra Cornell, who donated $500,000 and a tract of land. With the help of state senator Andrew D. surprised the scientific community by reporting that they had built a laser that could turn on and off 15 billion times a second (15 gigahertz). Using a tiny, newly designed and fabricated "strained quantum well A quantum well is a potential well that confines particles, which were originally free to move in three dimensions, to two dimensions, forcing them to occupy a planar region. " laser, the Cornell scientists have now pushed the rate up to a breathtaking 28 gigahertz, the fastest ever for any laser. Theorists had doubted that quantum well lasers would ever approach such rates. The Cornell laser consists of several extremely thin layers of indium gallium arsenide Indium gallium arsenide (InGaAs) is a semiconductor composed of indium, gallium and arsenic. It is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide. separated by gallium arsenide An alloy of gallium and arsenic compound (GaAs) that is used as the base material for chips. Several times faster than silicon, it is used in high frequency applications such as cellphones, DVD players and fiber optics. barriers. These layers -- no more than 40 atoms thick -- serve as quantum wells, which confine electrons within their boundaries. The laser appears to owe its superior switching rate to the presence of indium atoms, which distort, or strain, the orderly gallium arsenide crystal structure. |
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