Which laser mirrors should I buy?


whatever shines best for infrared

mw36gonjjovs-pcdtp9vtcaIt might sound strange, but infrared light in the wavelength used by CO2 lasers does not reflect on regular mirrors. In fact, it just burns its way through a regular mirror.

So, you need another material for the 3 mirrors inside a laser cutter.

Several possible materials can be found in online shops:

  • Si Mirror: Silicon Glass Gold coated has a very good reflective index, however it is not very suitable for laser powers over 50 Watt. (lasts about a year before it should be replaced)
  • Mo Mirror: Molybdenum is by far the toughest material. It does not have the best reflective index but it is strong, requires the least cleaning and is an absolute must for higher power lasers. (lasts about 3 years or more before replacement is needed)
  • Cu Mirror: Reflectivity between that of Si and Mo, but stronger than Si. This material is easily scratched and some people make them in the DIY style (I wouldn’t do that)
  • K9 Mirror: Little can I say about this stuff… it is good for the trash bin. This is the lowest of the lowest quality and should be avoided.


When you look around online, there are good prices to be found on all models. K9 is a definite NO GO, Si and Mo are good mirrors and Cu is the most expensive.

I personally use Mo mirrors already on a 80W cutter for more than 3 years and never had to clean them. For 40W cutters I think Si would be the best choice.

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