Some lasers are red. Some are green. Some of us have even seen blue and purple ones. So what causes lasers to appear in different colors? We’ll look into this in this article.
Whether you’re researching a laser to buy or planning to build your own, you’ll come across the letters NM. Or the term “wavelength.” These are basically the same thing; nm is the unit we use to measure wavelengths, the letters nm represent a nanometer, one millionth of a millimeter, so it’s an extremely small unit of measurement.
Colors of Light and Wavelengths
Light is actually an electromagnetic wave. Imagine these electromagnetic waves as wavy lines; imagine a lightbulb emitting a bundle of these small wavy lines, and these are what hit your eye and show you the color of the light.
In the electromagnetic spectrum above, we see that the wavelengths of the rays decrease toward the right.
The human eye cannot see all wavelengths of color. We can see between 400nm and 700nm. For example, we can’t see with the naked eye the light emitted by TV remotes that use infrared light. We also can’t see radio waves. Nor can we see the X-rays used when taking an X-ray. We can see rays with a wavelength between 400 nanometers and 700 nanometers. As you’ll notice in the spectrum, the colors of the light we can see also have different wavelengths.
Red Laser Wavelength
Common red lasers typically emit light in the 630-670 nanometer wavelength range.
Green Laser Wavelength
Green lasers typically have a wavelength of around 532 nanometers and appear as the brightest color to the human eye.
Blue/Violet Laser
Blue-violet lasers operate in the 405-450 nanometer range; this wavelength was used in Blu-ray technology.
Why Do Lasers Come in Different Colors?
The color of laser light varies because different types of laser diode emit light at different wavelengths. The color of a laser beam depends on the energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital in the semiconductor material used to make the laser diode. The specific material used and the design of the laser diode determine the wavelength, and therefore the color, of the emitted light.
What Is the Difference Between Green and Red Lasers?
A green laser pointer emits green light because; laser pointers that emit green light typically use green laser diodes that emit light in the 532 nm wavelength range. Red-light-emitting laser pointers typically use red laser diodes that emit light in the 650-670 nm wavelength range. In the image above, the wavelength labeled on the laser pointers is listed as 650nm for the red laser and 532nm for the green laser.
Laser diodes (above)
Laser diode materials and wavelengths (above)
In conclusion: we can say that the color of laser beams depends on the type of diode used, or more precisely, on the wavelengths they can emit.
Related Questions
The color of light depends on the wavelength it carries, and lasers produce light at a single wavelength. Whichever wavelength is produced, the eye perceives that wavelength as a specific color.
The eye can only perceive wavelengths between roughly 400-700 nanometers. Rays outside this range, such as infrared, cannot be seen with the naked eye even if they’re a laser.
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