CO2 Laser Lense/Mirror Choices


  • If < 130W but > 40W, = CVD ZnSe
  • If > 130W = CVD ZnSe or GaAs
  • If <= 40W = cheaper PVD ZnSe lens.

Lens coating:

  • PVD = Physical Vapor Deposition
  • CVD = Chemical Vapor Deposition


  • Plano Convex (one side flat/one side convex)
    • Note: Curved side faces UP
  • Meniscus (one side concave/one side convex)
    • slightly smaller spot size
    • possibly cleaner engraving
    • possibly worse cutting

Focal length criteria:

” The greater the degree of detail of the graphic, the shorter the focal distance during laser engraving. The thicker the material during laser cutting, the greater the focal distance”

  1. clearance between the cutting bed and the cutting head.
  2. The port size of the cutting nozzle (longer focal lengths produce a larger column as the beam converges toward the focal point. This can lead to the beam clipping the cutting nozzle if it doesnt fit through the opening. This really should only be an issue on the 3-4″ lenses if your lens is near the nozzle, and on 1.5″ if lens sits in tube above nozzle. See #3.
  3. Where your lens physically sits. If it is down in the nozzle, longer lenses will still be too wide as they pass through the nozzle, clipping the beam. If the beam is in the tube above the nozzle, you might not be able to get the work-piece close enough to focus. The focal length is the distance from the lens to the workpiece (not from the nozzle).

Focal length impact:

  • Shorter lengths may cut better IME because the air assist is closer and more forceful around the cut
  • Longer lenses = focal range — which is the length of the focused beam after convergence but before divergence) for cutting thicker materials


Si Mirror
Silicon Glass Gold Coated. Good reflective index for our machines (less than 50w)
High reflective index, needs cleaning more often.

Cu Mirror
Copper mirror, better than MO, a bit below SI when talking about reflective index

Mo Mirror
Molybdenum mirror. Can withstand alot of “abuse” but have less reflective index than the SI-mirrors.
Good for up to 100w+ lasers.

K9 Mirror
This is the worst mirror you can ever put in your machine. Bad reflective index and really easy to damage with dust or mishandling.
Theese K9 is often mounted in the K40 on delivery.