Green diode lasers are laser diodes that use semiconductors, similar to light-emitting diodes (LEDs), made mostly from indium. These lasers produce green light that is between 520 nanometers and 540 nm. They are used in laser pointers, for both presentations and surveying, and in laser movie projectors. Unlike red diode lasers, which also are commonly used in laser pointers, green lasers have less spread, so they are able to project farther with low-power systems and are better for use in sunlight.
When diode lasers were first made, red was the only color available. Then blue came around and, almost 15 years later, green diode lasers were created. Green diodes use a complicated set of semiconductors that must be made with materials that do not alloy well together, causing complications in development. The primary ingredient in green laser diodes is indium, a rare post-transition metal. The other primary ingredient, gallium nitride, diffuses green light, making it difficult to create green lasers. To create green laser light, these diodes must produce light that is from 520nm to 540nm.
While green diode lasers are one of the newest laser diodes, it is used in many applications, primarily laser pointers and projectors. These laser pointers are used by business people during presentations and teachers during class to bring attention to certain aspects on a board or projected presentation. Land-surveying personnel use more powerful laser pointers to survey the land. Laser projectors, used to project movies, make use of green diodes to create a fuller range of color.
Red lasers were commonly used for early laser pointers, but green offers several advantages that red lasers are unable to mimic without using substantially more power. Green diode lasers have a much thinner spread, so more power is focused in the main laser, rather than having a large amount of dispersed light, as with red lasers. This means green lasers can reach farther, even if the laser system is using less power. Green lasers also are useful in sunlight, because the laser is easily visible.
Some green lasers are not true green diode lasers. Instead, they are created using a complex set of components that are able to manipulate the wavelength of a laser and turn it into a green laser. For example, if an infrared laser is used and a nonlinear crystal is used to increase the frequency but lower the wavelength, the infrared laser can become a green one, though it is not a true green diode laser.