What is the best mirror choice for CO2 TEA lasers pulsing in the MW range?

[GregR]

I bought a used TEA CO2 laser and it needs optics. It is supposed to pulse in the megawatt range. The seller said that he had used moly mirrors from a machine shop previously and that they could get damaged and show the damage by having the laser burn pattern in them.

On eBay there are a variety of choices of mirrors off of high power CO2 lasers. Some are water cooled. Some have a TRZ. Others have no coating, or a gold coating. If there is a gold coating does it matter what the underlying metal is for the mirror--is stainless steel okay?

What works for mirrors for the CO2 TEA laser in the MW output power range? Any other suggestions and advice is greatly appreciated.

[helium]

The CO2 TEA lasers I worked on some time back used copper for the rear mirror.

[GregR]

For the copper rear mirror, did you need to cool it? Is there any special curvature required or is a flat copper air cooled used mirror okay? Do you have any pictures of your some time back devices?

[helium]

A chilled water internal heat exchanger / axial fan setup kept the cavity cool. The rear mirror and front optic mounts were bolted onto this cavity. The fans kept the mixed gas circulating and the heat exchanger ensured everything remained at a constant temperature for optimum performance. The rear copper mirror was housed in a large aluminum mount and seemed to be flat but I can't tell you this for sure. I often polished these myself using very fine abrasives, I guess the manufacturers would frown on this practice but when a laser is down and the production manager is barking in your ear............Sorry, I don't have any pictures to hand, I don't work on this stuff any more, but I'll have a look and see what I can find.

[planters]

What is the average power? This will determine the need for thermal management ie. water, convection or metal conduction. The peak power is high and if you have a guess as to the spot size on the mirror (the burn patterns on the moly mirrors might help ) then you have a peak/cm^2. With this info I would go to the short list of commercial IR optics manufacturers and ask the tech dpt. for a mirror recommendation. Sometimes the eBay source is not cheaper and at least you might learn what to avoid and what should work. Lastly, with these high intensities you do need to assure the optic remains scrupulously clean.

[helium]

GregR, is this a Laser marker you bought? The laser marker system I used to work on had an average power of 150W. The dimension of the beam emitted from the front optic was about 25mm x 19mm. The beam was steered to a mask made from brass and then focused on the product. Due to the size of the beam profile (before foccusing) the laser could still manage a reasonable mark with fairly shot optics.