Page 107 - Photonics Essentials an introduction with experiments

Source: Photonics Essentials

Chapter
6

Light-Emitting Diodes

6.1 Introduction

Light-emitting diodes (LEDs) can be used for displays, for signals
such as traffic lights, or for sending information at very high frequen-
cies. Of course, all of these applications could be grouped under the
heading of communications. LEDs have been made and sold for
decades. Recent innovative research has led to dramatic improve-
ments in LED output power and efficiency. The situation has evolved
to the point that it is now clear that LEDs will be used in some light-
ing applications by displacing the tungsten light bulb. The commer-
cial stakes in this industry are very high; in my opinion, even higher
than those in the communications industry. This application of LEDs
may solve an important problem faced by engineers in optoelectron-
ics, a marketing problem: how to achieve product sales volumes that
grow faster than product prices decline. This is a requirement for the
existence of a business.
The circumstances imposed by the communications industry have
led to the simultaneous development of high-reliability lasers with
continuously improving bandwidth and, at the same time, optical
fibers with reduced loss and dispersion. Initially, a result of this
progress was to reduce the need for large numbers of optoelectronic
devices in optical fiber telecommunications systems. As a result, mak-
ing a growing business out of the design and manufacture of optoelec-
tronic components like detectors, LEDs, and lasers for telecommuni-
cations has not been a simple task. During the past few years, the
explosive growth of the Internet has prompted network equipment in-
stallers to develop wavelength-division multiplexing. Basically, this

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