Jan. 28, 1958: a laser is born: the use of a diffraction grating for mode selectivity captured the imagination of Arthur L. Schawlow, one of the laser's inventors

Article Abstract:

The laser, which is a device for light amplification by stimulated emission of radiation, is only a few decades old. The idea of the laser grew out of work done by Charles H. Townes in the 1950s. Townes was working on masers, which involve microwave amplification. In 1957, Townes and Leonard Schawlow discussed the possibility of infrared or even visible-light lasers. At the time, mode selection was a major problem to be overcome, and an entry in Schawlow's notebook on Jan 28, 1958 (reproduced in an illustration accompanying the article) is therefore of particular interest. The entry describes how to achieve mode selection by using the shape of the resonator's cavity and it indicates that selectivity can be increased by using a diffraction grating. By the year 1960, Schawlow's ideas were shown to be valid and optical masers were a reality. On Mar 22, 1960, Schawlow and co-worker George Devlin were awarded US patent No 2,929,922. Soon after that, commercially available lasers appeared. For their work in these areas, Townes shared the Nobel Prize in Physics in 1969 and Schawlow shared it in 1981.

History, Scientists, Physics, Physicists, Lasers, Laser, Schawlow, Arthur Leonard, Townes, Charles

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Expert opinion: the barrier to high performance is no longer bandwidth

Article Abstract:

Trends in Gbit networks, high-speed digital transmission on copper-based systems, fast-packet transmissions on wide area networks (WANs) and advances in cell-relay services are discussed. Advancements in very-large-scale integrated (VLSI) circuit and lightwave technologies are enabling the development of G-bps networks with negligible error rates and low delay. Consequently, the obstacles to speed now are the processing rate of communications protocols and the efficiency of algorithms to minimize buffer overflow and packet-loss. New technologies to provide high-speed communications over twisted copper wire are the high-rate digital subscriber loop and its asymmetrical digital subscriber loop variation, which respectively provide 1.5M-bps and 1.544M-bps performance. Fast-packet technology is now providing WAN access speeds in the tens of M-bps range. Developmental requirements and competing service definitions for cell relay services are briefly discussed.

Packet switches, Telecommunications transmission technologies, Wide area networks, Business conditions, Trends, Performance, Packet Switch, Data Communications, Review of Past Year, Twisted Pair, WAN

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