Do you own a DVD or CD player or even a printer? What about the remote control that powers your TV? Each of these household tools features a laser diode. This is a semiconductor device that emits waves of the same frequency and phase when energy flows through it. The light beams from laser diodes are not the pencil-shaped beams of mass destruction you might imagine. Instead, they emit broader, cone-shaped beams of visible or infrared light. They are low density beams. They are small devices usually less than a millimeter in size with minimal power requirements. A crystal wafer featuring p- and n-type regions is one such feature, and it is this feature that classifies it as a semiconductor rather than a solid-state laser.
Diodes are like LEDs. In fact, LEDs have been described as lasers without feedback cavities. Laser diodes have internal or external cavities that are used to trigger the action of the laser. High Q cavities narrow the emission lines and beams. These beams are not as sharp or narrow as gas lasers.
Laser light and colours
These emit visible or infrared light. Colors range from blue, blue-violet, and green to red. The use of a laser diode depends in large part on its wavelength and position on the light spectrum. For example, Blu-ray players use blue-violet 405nm laser diodes while red laser pointers use laser diodes in the 635nm range.
Common uses
Laser diodes, which are very small, are the most common type of laser. They are found in the items listed above as well as barcode readers, fiber optics, optical mice, range finders, laser pointers, and medical equipment.
Safety issues
While not as dangerous as gas or solid-state lasers, they still need to be used with caution. In some cases, such as CD and DVD players, the laser diodes are located inside the unit and are not intended to be seen. In addition, its low output beams are nearly invisible and highly contrasted. In contrast, laser pointers have a higher output and are very visible. Laser pointers are collimated, and high-energy laser pointer rays can burn the retina. Laser pointers can also cause less substantial effects such as headaches, after-image, and visual distraction when not used properly.
There is a greater risk associated with higher energy visible and infrared diode lasers. Even invisible beams can be dangerous if they are balanced. Because of the potential for eye injuries or burns, it is wise to use caution around a diode laser. Never look into the laser beam or point the laser pointer into another person’s eyes. Watch for reflected lasers, too.
Small, powerful and useful, it is becoming increasingly popular. In many cases, you will never see the ray, but you should be aware of it and avoid the temptation to look at it or alter it in any way.