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Powerful laser beams can be focused on a small area with enormous power density(1). Which means the focused beams can readily heat, melt, or vaporize material quick and accurately(1). Lasers have been used, for example, to drill holes in diamonds, to shape machine tools, to trim microelectronics, to heat-treat semiconductor chips, to cut fashion patterns, to synthesize new material, and to attempt to induce controlled nuclear fusion(5). The powerful short laser pulse also makes possible high-speed photography with an exposure time of several trillionths of a second(5). Highly directional laser beams were used for alignment in the construction of the Bay Area Rapid Transit system in San Francisco(5).
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