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What does nm Mean in Lasers (and Light)?

What does nm Mean in Lasers (and Light)?

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In a previous article, we discussed the significance of the mW (Milliwatt) measurement when it comes to laser technology.

Another one that you would frequently encounter is the ‘nm’.

What is it and why is it important?

nm stands for nanometer, which is equivalent to a micrometer (1×10−9 m). It is used to measure the wavelength of lasers.

What is nm in Lasers?

The nm stands for nanometer, as recorded in the International Bureau of Weights and Measures. It is a measurement unit within the metric system.

Formerly known as the milli-micrometer or milli-micron, it is 1/1000 of a micron, which is equivalent to 1 micrometer. Now, the common measurement of nm is used instead, denoting a unit that is one-billionth of a meter; you will also sometimes see it written as 0.000000001 m or 1×10−9 m.

This unit of measurement is mostly used for dimensions that need to be measured on an atomic scale, certainly too tiny for mundane rulers or measurement tapes. For example, it could be used to measure the diameter of a helium atom or more relevant to this article, the wavelength of a laser.

The nanometer is also commonly used to specify the wavelength of electromagnetic radiation within the visible part of the electromagnetic spectrum. The visible light ranges from around 400 to 700 nm.

Understanding the characteristics of a laser and the wavelengths required to produce various colors is useful because these are often listed in a laser pointer or laser tool’s specifications.

Lasers - Wavelength (nm) Explained

What is the Wavelength?

A wavelength is a concept in physics that reflects the wave character of matter. All matter and energy have properties that resemble both waves and particles.

The wavelength is the distance between two successive crests or troughs of a wave, as measured in the wave’s direction. In other words, it is the distance over which the shape of the wave is repeated.

Wavelength is influenced by the medium that the wave travels through. Common media known to most people would be water, air, and a vacuum. Waves that you might be familiar with are light energy, water waves in the ocean, sound waves, and electrical signals transmitted through a conductor (such as high-voltage power cables).

Sound waves reflect a difference in air pressure, while light waves reflect variations in the strength of the surrounding electromagnetic field. As you may have deduced by now, wavelengths of laser are influenced by variations in electromagnetic radiation.

What is the Wavelength of Light produced by the Laser Pointer?

Visible light comprises a range of wavelengths from 400 to 700 nm. The human eye is most sensitive to visible light with a wavelength of about 555 nm. Obviously, the light beam produced by laser pointers falls within the above range of wavelengths so as to be easily detected.

Further, each color is produced by wavelengths of different nm. One thing to take note of is that a laser’s wavelength or color does not always directly relate to its power output.

Here, we will be exploring the different nm ranges based on the colors they are categorized under.

Red / Orange

Lasers that are tinted red, orange or any shade in between were the earliest types of laser pointers. Even today, many basic laser pointers or tools are in this color spectrum. In terms of power output, red or orange lasers are more or less harmless but you still should not point them at a person’s eyes.

On the lower end, you will find red/ orange lasers within the 630 to 680 nm wavelength that have rather short-range and low power output (less than 5 mW). However, there are also red/ orange pointers that boast a range of up to a few miles and power output of up to 200 mW.


A lot of laser tools or pointers are of the green spectrum today. This is because a green laser beam is VERY visible. They’re often brighter than red/ orange lasers and have incredible range.

Even at below 5 mW in power output, you could point a green laser pointer into the sky and it would be seen from far away.

Green lasers typically have a wavelength of about 532 nm. The high-powered ones will generally be restricted at Class 3A and above – do not use them near an airport!


Blue lasers are commonly used in HD video technology, such as Blu-ray drives. To be precise, Blu-ray actually uses violet-colored lasers that have a short wavelength of 405 nm, which makes them barely visible.

In contrast, blue lasers have a wavelength of about 500 nm. Some really high-powered blue lasers are categorized as Class 4 due to the hazards of operating them.

Improper use will cause permanent damage to your eyes and camera sensors, even if it is pointed from a fairly long range.


Yellow lasers are rarely seen, even though they have been around for some years. They tend to be more expensive than laser pointers of other colors. This is due to the cost of using high-powered diodes and other quality components.

Yellow lasers tend to have wavelengths of about 593.5 nm. Power output ranges from relatively low levels of 2 mW up to an incredible 50 mW- be sure to check the safety information if you wish to purchase one!

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