Light-emitting diodes transformationalIt seems like only yesterday when I hitchhiked from Texas A&M University to Dallas in March 1966 to meet Ed Bonin at Texas Instruments. Bonin showed me a cylinder no larger than his thumb. When he pressed a button at one end of the device, red light emerged from a tiny crystal installed in the opposite end.
This was a magical moment. It was amazing to see light emitted by a crystal the size of a grain of salt powered by a small flashlight battery.
The crystal in Bonin's miniature light source was a light-emitting diode, or LED, a device that emits light when electricity passes from one region of the crystal to another.
In 1961 Texas Instruments developed powerful LEDs that emitted invisible near-infrared light just beyond the red that we can see. These LEDs eventually evolved into the infrared light sources used in TV remote controllers, intruder alarms and military night-vision devices.
Meanwhile, Nick Holonyak Jr. had a clever idea. Holonyak worked for General Electric, the company cofounded by Thomas Edison in 1892. Edison developed the first commercially successful incandescent electric light, and in 1962 Holonyak followed in Edison's footsteps by developing the first practical LED that emitted visible light.
In 1963 Holonyak became a professor at the University of Illinois, where he trained students who went on to develop improved LEDs and lasers.
Holonyak's pioneering LED work led to the development of many kinds of red, orange, yellow and green LED indicators and readouts that displayed numbers and letters.
The blue LED completed the spectrum and permitted the development of giant display screens and advertising signs.
The white LED arrived when blue LEDs were coated with a phosphor that glows green and red when illuminated by blue light. Mixing these colors produces white light.
Today LEDs are everywhere. The monitor of the computer into which this column was typed is illuminated by LEDs. Many traffic signals and car tail lights use bright LEDs. Flashlights that employ white LEDs are much brighter than incandescent flashlights and use much less power. You can now buy long-lasting LED lamps for household use.
Holonyak received the National Medal of Science, the National Medal of Technology and various other awards for his innovative developments of LEDs and lasers. More information about the program is available on the web site at www.hmhid.com.