Radiant energy sources include both coherent and noncoherent sources. Noncoherent sources are typically traditional light sources for illuminating applications, but also include light-emitting diodes. Lasers, on the other hand, rely on coherent emission that produces a beam that is highly collimated and highly monochromatic.

Semiconductor laser diodes represent a class of lasers especially useful in optical computing applications, optical sensors, optical disc systems, and materials processing. They are small and highly efficient. When the laser diode is forward biased, incoherent light emission takes place until the drive current reaches a threshold value. Below threshold, the device is similar to a light-emitting diode (LED). Above threshold, lasing takes place and the light output increases rapidly with current. A completely new segment on semiconductor laser diodes begins on p. 9.31.

This section also includes a chapter on cathode-ray tubes and electroluminescent displays, with valuable complementary material on the accompanying CD-ROM covering electro-optics and nonlinear optics, phosphor screens, photoemissive electron tubes, and camera tubes.

Four chapters treat radiant energy sensors. Photoconductive and semiconductor junction detectors convert electromagnetic energy to electric energy. Charge-coupled-device and charge-injection-device image sensors are applicable to high- and low-light-level imaging, spatial character recognition, and facsimile reproduction. Infrared detectors include both thermal detectors and quantum detectors, and often require cryogenic cooling to reduce...