Common laser wavelengths and their uses
Tuesday, November 02, 2021
Before we dive in, let’s rewind to the height of summer. You’re driving on a beautiful drive on a sunny summer day, and you catch yourself wondering: Can I get a sunburn through my car window?
It turns out that car windows are pretty effective at blocking UVB (280-315 nm) rays, which are of a shorter wavelength than visible light (approx. 380-750 nm). Those same car windows are of course nearly 100% transparent to visible light.
You’ll see that choosing the right wavelength for the right material is half the battle when it comes to lasers. Let’s illustrate that by looking at 3 real-world applications of lasers: telecommunications, laser welding, and eye surgery.
In telecommunications, information can be transmitted literally at the speed of light via an optical fiber. The wavelengths that are most prevalent are 1,310 nm and 1,550 nm. Why these wavelengths? Well, let’s see what’s important in fiber-optic communication.
These 2 requirements are in fact closely tied and could be rephrased as: choose a wavelength that doesn’t get absorbed by the optical fiber. 1,310 and 1,550 nm both fit the bill!
In the case of welding, our imperative is the opposite: Melt the target!
Some common wavelengths used in laser welding are the 1,064 to 1,070 nm produced by Nd:YAG and Ytteribum-fiber lasers and the 10,600 nm wavelength produced by CO2 lasers.
In a nutshell, if you shine a laser of an appropriate wavelength at the junction between 2 components, the materials will heat up and melt together as the energy in the laser light gets absorbed.
Because steel does not absorb every wavelength equally, it is important to choose a wavelength that is absorbed for it to heat up effectively. You could look up some absorption coefficient charts and notice that steel and iron absorb 1,064 nm decently well, but 10,600 nm even better. However, that doesn’t mean CO2 lasers are always the perfect choice.
Wavelength is important, but there are other important considerations, some of them practical (cost and ease-of-use), others more technical. Gentec-EO partners with the automotive industry to help ensure they get an effective weld every time. You can read more about that here.
In the case of our eyes, we need a bit more finesse. We need to very precisely cut and remove some parts, but cannot recklessly heat, distort or destroy the surrounding tissues. 193 nm ArF Excimer lasers allow for such precise cuts and a minimum amount of thermal distortion.
Laser eye surgery to correct near-sightedness, far-sightedness and astigmatism uses this 193 nm Excimer laser to change the shape of the cornea, one of the lens’ of the eye. It does this by selectively cutting away small bits of the cornea in order to flatten or steepen it.
This is just a glimpse of the many different laser wavelengths used today. Other wavelengths are useful for remote sensing technologies such as LIDAR, cosmetic surgeries such as tattoo and hair removal, manufacturing techniques for electronic chips, and a host of other applications.