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Answer: Although light-emitting diodes and laser diodes sound similar – in fact, both are made of semiconductor materials – they are very different beasts, designed to behave in different ways and to tackle different jobs. Laser diodes take the form of a semiconductor material between what is essentially a pair of mirrors. The region between the mirrors is called the resonator cavity. When electricity goes through the semiconductor, it gives off photons, which then bounce back and forth inside the cavity, exciting other nearby electron-hole pairs to release more photons at the same wavelength. The light increases continuously in intensity, with the photons marching in lockstep together as they oscillate between the two mirrors. If one of the mirrors allows just a small fraction of the light to escape some of the photons exit. All at same wavelength and in phase, they produce an extremely narrow column of pure, bright light at a single wavelength. In physicists’ terms, the photons are coherent. This extremely well defined beam is one of the main characteristics of a laser. As such, it is something like a scalpel: sharp, thin and able, with proper optics, to do delicate work, such as reading the fine pits on a compact disc or scanning the bar codes in a checkout line. By comparison, the widely scattered light of an LED is like the pattern of raindrops. Because LEDs are not in a proper cavity (that is, not between mirrors), the photons they emit are, in a sense, incoherent. Light comes out not in a unidirectional column but in a broader, more diffuse pattern, composed of a spread of wavelengths from one area of the spectrum. The photons an LED produces may not be all at the exact same wavelength, but they are close enough so that they are perceived by the human eye as being the same color. 1. M. George Craford, Nick Holonyak, Jr., Frederick A. Kish, Jr., "In Pursuit of the Ultimate Lamp." Scientific America, February 2001, p. 65. Do you have an LED lamp question? You can e-mail your LED lamp questions to our application engineers at: click
here to email us. Founded in 1983, LEDtronics leads where others only follow when it comes to designing, manufacturing and packaging state-of-the-art LEDs to meet the world’s constantly changing lighting needs. Our inventive product line encompasses an array of direct incandescent lamp replacement Based LED lamps, low-cost snap-in and relampable Panel Mount LED lamps, high intensity sunlight-visible Discrete LEDs, circuit board status indicators (PCB LEDs), surface mount diodes (SMT LEDs), full-spectrum rainbow RGB LEDs and Infra-Red (IR) LEDs. Visit the Future of Light on the Web at: www.LEDtronics.com
You can e-mail your LED lamp questions to our application engineers at:
www.LEDtronics.com.
Founded in 1983, LEDtronics leads where others only follow when it comes to designing, manufacturing and packaging state-of-the-art LEDs to meet the world’s constantly changing lighting needs. Our inventive product line encompasses an array of direct incandescent lamp replacement Based LED lamps, low-cost snap-in and relampable Panel Mount LED lamps, high intensity sunlight-visible Discrete LEDs, circuit board status indicators (PCB LEDs), surface mount diodes (SMT LEDs), full-spectrum rainbow RGB LEDs and Infra-Red (IR) LEDs.
Visit the Future of Light on the Web at: www.LEDtronics.com
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310-534-1505/800-579-4875
webmaster@ledtronics.com
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