APPLICATION

The main features of a laser beam are (1) high directionality, (2) narrow spectrum (monochromatic), (3) coherence, (4) high power density, and (5) high switching speed.

A laser is attractive for its small size, high efficiency, and low-voltage operation. It can be operated in CW mode for low-power applications and in pulse mode for high-power applications. The laser is indispensable as the light source for advanced optical-fiber communication whose main advantage is large bandwidth. The optimum choice of wavelength is between 1.3-1.5 for this purpose. A modulation rate of higher than 20 Gb/s has been demonstrated. Another related application is direct-beam communication, e.g., between satellites. A laser is also useful in laser radar systems, in f range-finders for terrain profile, in military navigation, tracking and guidance systems, and in intrusion alarm systems. It is important for holography where three-dimensional images can be stored and retrieved. The highly directional beam is useful for precision alignment, and with extremely high power density it can be used for cutting metal, drilling (also for wood and ceramics), and welding. The metal interconnections in ICs that serve as fuses can be burnt off by a laser beam. Lasers are also used in the medical field for surgeries, such as retina repair and in cancer research. It is a good analytical tool in chemical-emission spectroscopy such as exhaust and pollution analysis, and for meteorology. In more common commercial applications, it is used in compact disc (CD) audio and video players, copy machines, and printers. One shortcoming of lasers is that they cannot be easily fabricated in an integrated circuit for monolithic optoelectronics.