What is a Green Laser?

S. Mithra

A green laser has more versatility, strength, and brightness than traditional red lasers. This color of laser can be produced in a small, handheld tool that looks like a miniature flashlight. Amateur astronomers often use a green laser because it reaches so far into the atmosphere, with a visible beam, that you can point out stars and galaxies.

Green lasers are more versatile than red lasers.
Green lasers are more versatile than red lasers.

Lasers are powerful lights where every wave, or piece, of light has been precisely lined up into a solid beam. Such light is said to be "collimated," or made into a column. Different colors of light, and lasers, are determined by the size of those tiny waves, called the wavelength. The popular red laser has a wavelength of 650 nanometers, that our eyes perceives in the visible spectrum as red. However, green light has even more energy in a wavelength of a minuscule 532 nanometers.

Misuse of a laser, including a green laser, can permanently damage a person's retina.
Misuse of a laser, including a green laser, can permanently damage a person's retina.

A green laser has several advantages over a red laser. First of all, green is closer to the center of the visible spectrum, so it's easier for our eyes to perceive the color at night. Since it has more energy, it can travel farther to project a small dot on low clouds and far off hillsides 9,000 feet away (2,740 m). The tool can form a visible beam even without fog or dust to exaggerate it. A green laser looks as much as 50 times brighter than the red equivalent.

During star parties, backyard astronomers using small telescopes prefer a green laser to point to particular constellations, galaxies, and stars because the beam reaches so far into the sky. A green laser is especially compatible because it doesn't interfere with dark adaptation, or how our eyes become more sensitive to dim light in persistent darkness. Astronomers opt for strengths around 5 milliwatts, which is a high powered laser. Yet machines that deliver fun laser light shows might use a much weaker strength, such as 1 milliwatt, to reduce the potential for harm.

The process of forming laser beams out of laser diodes is complicated. Special crystals must filter and focus the light to get it to the right wavelength and perfectly collimated. Red lasers use direct injection laser diodes, yet a green laser requires more steps so they are more expensive. Then again, the process can be more tightly controlled. Some models allow you to pulse the light, so it's released in spurts and makes a dotted line. Others let you focus the green laser, so the circle creates a tiny dot no matter the distance of the object on which it falls.

Using a green laser, just like a red laser, requires safety precautions. Even a quarter of a second exposure to your eyeball can permanently damage your retina. Never point a laser along the ground where it can encounter cars, people, or pets. Purchase a strength compatible with your intended usage, and don't let children play with lasers.

A green laser is preferred by backyard astronomers using telescopes to point to stars and constellations in the sky.
A green laser is preferred by backyard astronomers using telescopes to point to stars and constellations in the sky.

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Discussion Comments


During a routine traffic stop in the mid 2000's, I once had a Law Enforcement Officer or LEO commit a noticeable anomaly in that he retained me there until another unit arrived who had one of these hand-held green lasers and he used it to inspect/ verify/ do something inside my mouth because he asked me to open my mouth, and then, he appeared to shine it around upon my teeth, my tongue and so forth for a few seconds while he diligently looked therein. It was/is an event that still bothers me to this very day in that I've never, ever heard of such a thing occurring before and I've since then read that within a range of about a foot or so, these high-powered green lasers can ignite an unlit match after several seconds of shining sad laser directly upon the "head" of the match because of the heat produced therein. So, maybe he was trying to surreptitiously cause injury to the inside of my mouth by burning it in some manner?

I do not know what he was doing. It was a very strange incident, indeed, I must admit, but, I'm still looking for an answer to the following question:

Is there any kind application (at all) that you know of for why said LEO would have done as such?

I ask, in that it makes a difference to me between knowing that there is some sort of legitimate answer to my question, or he was trying to feloniously assault and batter me in a manner which would have "plausible deniability", as to whether he had actually done such a thing because it could be written off as a burn caused by some sort of hot consumable item or some sort kind of self-inflicted wound. I do not remember having any sort of burn inside my mouth, afterwards, and that fact actually bugs me even more, but, for now I'm just wanting an expert opinion as to whether or not there is a legitimate purpose for such a thing to have happened.

Thanks in advance - C


It's not OK to point these things at cars (whose drivers can stop, get out of, and kick the butt of the clown shining a laser) but it's OK to shine them into the sky where there may be passenger planes whose pilots can be blinded by the green laser of someone on the ground pointing at stars like he/she is at the planetarium?


Should I buy a green laser pointer online?


Can someone elaborate on the burning capabilities in regard to greenlight laser turp, like on the photoselective vaporization of the prostate? Apparently the green light marks the tissue containing hemoglobin but once reaching the prostate capsule ceases since there is no hemoglobin in that tissue. Why a green light for the procedure?


It's not true that a green laser doesn't interfere with the eye's dark-adaptation. What is true is that the light level of the green laser's beam reflecting off of atmospheric dust is generally not enough to significantly reduce dark-adaptation. The same would be true of a white flashlight as long as the beam wasn't pointed at the eye or at something that bounces a lot of the light back to the eye.


What is the normal ma setting for a green laser to achieve the burning capabilities? I know that red is around 380 and blue at 100 to 110. Also is the green produced by using a red diode and then filtering it through the crystals? Knowing that is a high power diode what happens if you strip the crystals away? Can you build a high power red laser as well?

Thanks, Brandon

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