What is a laser diode?
Do you own a DVD or CD player or even a printer? How about a remote control that controls your TV? Each of these household items features a laser diode. It is a semiconductor device that emits waves of equal frequency and phase when power flows through them. The light beams emitted by laser diodes are not the pencil-shaped beams capable of mass destruction that you might imagine. Rather, they emit wider, cone-shaped beams of visible or infrared light. They are low intensity rays. They are small devices that are typically less than a millimeter in size with minimal power requirements. A single crystal wafer comprising p-type and n-type regions is one of their characteristics, and it is this characteristic that classifies them as semiconductor rather than solid-state lasers.
Diodes are similar to LEDs. In fact, LEDs are described as lasers without feedback cavities. Laser diodes have internal or external feedback cavities that are used to trigger laser action. High-Q cavities narrow the emission lines and beams. These beams are not as sharp or narrow as gas laser beams.
Laser light and colors
They emit visible or infrared light. Colors range from blue, blue-violet and green to red. The use of the laser diode depends largely on its wavelength and its position in the light spectrum. For example, Blu-ray disc players use blue-violet 405nm laser diodes, while red laser pointers use laser diodes in the 635nm range.
Common uses
Durable and small in size, laser diodes are the most common type of laser. They are found in the items mentioned above, as well as in barcode readers, fiber optics, optical mice, rangefinders, laser pointers, and medical equipment.
Safety issues
Although they are not as dangerous as gas or solid-state lasers, they must be used with care. In some cases, such as CD and DVD players, the laser diodes are located inside the device and are not meant to be seen. In addition, their low-power beams are nearly invisible and highly divergent. In contrast, laser pointers have higher power and are highly visible. Laser pointers are collimated and it is possible for the powerful beams of the laser pointer to burn the retina of the eye. Laser pointers can also cause less significant effects such as headaches, afterimages and visual distraction when not used properly.
Greater danger is associated with the more powerful visible and infrared diode lasers. Even invisible rays can be dangerous if collimated. Because of the possibility of eye injury or burns, it is wise to exercise caution whenever a diode laser is present. Never look into the laser beam or point a laser pointer into another person’s eyes. Be aware of reflected laser beams as well.
Small, powerful and useful, they are becoming more and more common. In many cases you will never see the beam, but you should be aware of it and avoid the temptation to look at it or alter it in any way.
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