The laser wavelength chart explained
Monday, November 07, 2022
They say an image is worth a thousand words. That’s certainly true of the laser wavelength chart. Full of colors and packed with information, it allows you to compare different lasers at a glance.
We’ll be using Wikipedia’s version for this article. It’s not complicated, but it does take a bit of explaining.
Let’s dive in!
Image source: https://en.wikipedia.org/wiki/File:Commercial_laser_lines.svg
Who’s got the power?
One key laser parameter you’ll want to know is: how much power can this laser deliver?
This laser wavelength chart indicates the available power (and energy) levels by the length of the lines. The scale is on the left-hand side. Take note that it is a log scale.
CW (solid line) vs pulsed (dotted line)
You may know already that lasers emit light in two ways. They can emit light continuously (CW) or in short bursts, called pulses. Average power measurement is mainly used for CW lasers. Peak power and energy measurement make more sense for pulsed lasers.
On this chart, lasers that can operate as CW lasers will have a solid line. Lasers that operate more commonly as pulsed lasers will have a dotted or checkered line.
As an example, the left-most F2 Excimer laser is a pulsed laser. At the time this laser wavelength chart was made, it could reach max energy levels around 300 mJ.
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The importance of wavelength
Choosing the right wavelength is of critical importance. What’s best for cutting shipping‑grade steel won’t be best for delicate jewelry engraving.
Wavelength is inversely correlated with photon energy. This chart lists short-wavelength (high-energy) UV lasers on the left. Long-wavelength (low-energy) infrared rays are on the right.
Thin and thick lines, what do they mean?
Some lasers emit light in a very narrow spectrum of wavelengths. All the lasers with thin lines (i.e. the top half of the chart) are in that category. As an example, if you buy a CO2 laser, its optical components will age. The laser’s power output and beam profile will vary with time, but its output wavelength will always hover around 10.6 µm.
On the other hand, some lasers are tunable lasers. This means that the user can actually change the wavelength at will (within certain limits). As an example, Titanium-sapphire (Ti:sapphire) lasers can emit anywhere between around 650 and 1100 nanometers.
Lasers with multiple lines
By using frequency-conversion crystals, one wavelength can be transformed into another. For instance, you can note that the Nd:YAG laser has its main line at 1064 nm, but also has a frequency-doubled line at 532 nm, and a frequency tripled one at 355 nm. Frequency conversion broadens the range of action of tried-and-tested of tried-and-tested industry workhorse lasers like the YAG.
Other lasers have multiple lines simply because the laser itself emits at different wavelengths. We can again use the Nd:YAG as an example. This laser has frequency-converted versions of the main 1064 nm line, as discussed in the previous paragraph. But it also has secondary lines that happen naturally (without any frequency-conversion), such as the 946 nm and 1319 nm lines.
There is much more to be said about lasers, and even more is being discovered all the time, but the laser wavelength chart certainly gives you a good standing point and a great visual representation.
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