Webster`s Ninth New Collegiate Dictionary defines optoelectronics as the branch of electronics that deals with electronic devices for emitting, modulating, transmitting, and sensing light. Such devices include semiconductor lasers, light-emitting diodes, detectors, fiberoptic components, optoelectronic integrated circuits, and liquid-crystal displays. And according to some definitions I`ve seen, cathode-ray tubes could be included--although at Laser Focus World we tend to limit ourselves to solid-state devices.
However you define it, the technology that combines photons and electrons in single components is playing an increasingly important part in our lives. Integration of semiconductor lasers with modulators, for example, is a key element of current telecommunications systems, while the evolution of flat-panel displays into viable commercial devices results from continuing optoelectronic advances and refinements. Recognizing the significance of optoelectronics, we begin a series of supplements this month. Optoelectronics World will allow us to provide more-detailed coverage of this technology, emphasizing different aspects of optoelectronics in each issue--we begin with a close look at detectors. The supplement is separate from, but mailed with, this issue of the magazine--so if your copy is missing, please contact Carole Root by e-mail: [email protected].
Directed energy drives new applications
For decades, lasers have inspired science fiction writers to "invent" a host of different techniques and devices to take advantage of directed-energy beams. Star Trek fans are familiar with the phaser--a directed-energy gun--and with the tractor beam, by which one spacecraft can "attach" itself to another for towing or other reasons. All fiction perhaps--but scientists at Edwards Air Force Base in California have succeeded in launching a small craft powered by a beam of directed energy from a ground-based laser; their ultimate goal is launching the craft into space (see p. 90). A significant advantage of this setu¥is that no fuel is expended lifting more fuel off the ground.
High-power diode lasers can deliver a controlled dose of thermal energy to a specific location. Their ability to direct energy in this manner has led to these lasers being described as high-performance converters of electrical power to light and high-quality spots of heat. As direct thermal sources, high-power diode lasers have numerous material-processing and medical applications, which means they are rapidly becoming one of the industry`s fastest-growing product segments. Reliability may become a key factor influencing this growth and will doubtless add more energy to the debate over the advantages or otherwise of aluminum-free devices (see p. 93).