Technical Library: YAG vs. CO2 Lasers

Two of the most common types of lasers you hear about are YAG and CO2. While Epilog manufactures a CO2 laser system, we wanted to give you some information about the two different types of laser systems and which one may be right for your application.

Both CO2 lasers and YAG lasers generate a very concentrated beam of light, but from there the lasers become very different in their uses and how they work. In this article we will first look at the different uses of the two laser types, and when each one is right for your application, and finally break down the benefits of each system.

What are the different uses for YAG and CO2 lasers?
YAG lasers and CO2 lasers react very differently on different materials because of the differing wavelengths of the laser beams. The wavelength of a YAG laser (1.064 microns) is exactly ten times smaller than the CO2 wavelength of 10.64 microns, which makes it ideally suited for absorption in most metals, but this small wavelength inhibits its ability to be absorbed by many other materials (wood, acrylic, plastics, fabrics, etc.)

A CO2 laser beam is not easily absorbed by metal, but can easily be absorbed by many organic materials such as wood, acrylic, rubber, etc, while it tends to reflect off of most metal surfaces. It's the different wavelengths of the two beams that are mainly responsible for the different types of materials that they will react with. There are a number of other differences between the two lasers; thermal efficiency, heat transfer, minimum and maximum power output, etc. and these characteristics all have an affect on the materials that the beams react with.

Will a CO2 Laser work on any types of metals?
Yes, the CO2 will work on certain metals in a couple of different ways.

1. Coated Metals
   Coated metals include painted brass, anodized aluminum, or any other metal that has been coated with a material that the CO2 laser beam will engrave away. Even a low powered CO2 laser is very effective at removing paint from most metal surfaces; with painted brass being a popular engraving material because of all the different colors available and the high contrast that is generated when it is engraved. However, some metal surfaces are painted with exceptionally hard paint coatings that even a 120 watt laser has difficulty engraving cleanly. The common products where you will see this are ballpoint pens, and anything that is powder coated.
   
   Another metal that is very popular with CO2 lasers is most anodized aluminum. When the CO2 laser beam contacts the anodize coating, it turns it white and provides excellent contrast on the many different anodized colors. Aluminum that is protected with a gold coating is probably not anodized (it's probably protected with a process called chromate conversion) and will not engrave well.
   
   CO2 laser systems are compatible with painted metals and anodized aluminum because of the high contrast, fast engraving speeds, low power requirements and the wide variety of projects that these materials lend themselves to.
   
   
2. Stainless Steel Metal Marking
   Until recently, marking stainless steel with a low powered CO2 laser was very difficult to do. The problem is that most of the CO2 energy is reflected from the metal surface and only a small amount is absorbed, providing a very faint or non-existent mark. In the last few years a couple of different companies have introduced products that allow low powered CO2 lasers to create a very dark, permanent mark on stainless steel. The products are known as Laser Marking Materials (LMM) and go by the common name of Cermark, or Thermark. The LMM is sprayed onto non-coated stainless steel from a spray can (just like spray paint!). The LMM is allowed to dry for a couple of minutes before it is ready to engrave.
   
   When the laser engraves on the Cermark, it permanently bonds the material to the metal, resulting in a permanent black mark. After engraving, the metal is washed with water to remove the excess spray. This simple process is often used for marking tools, medical instruments, and industrial parts with bar codes and serial numbers. LMM will also work with some other metals, but we suggest you test out any other material you are considering using to ensure the mark is acceptable. It is our experience that stainless steel is the most predictable metal for use with LMM.

Will a YAG Laser work on any types of non-metallic materials?
Unlike a CO2 laser, a YAG laser is compatible with only a limited number of materials. Because of its small wavelength, a YAG laser can mark many different types of metal, and a few plastics, but its effectiveness on standard CO2 products (wood, rubber, acrylic, etc) is almost non-existent. You will typically only find YAG lasers in industrial applications, with personalization applications limited mostly to high volume marking of products like ballpoint pens.

The reason that so many people are excited about the LMM discussed earlier is that there are a lot of stainless steel products that require laser marking and marking with a YAG laser is very expensive.

This was a quick look at YAG versus CO2 lasers. While both have applications that they are best for, if you would like us to run a test on a material and show you how a CO2 laser will work with it, you can contact our Applications Lab, or fill our our Request Form for more information.