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I'm searching for a notch (band-stop) filter (like [1]) for a 10.6 $\mu$m CO$_2$-Laser and I have yet to find one. Is there some physical reason such filters don't exist or is there just no demand?

The use case is to protect a far infrared camera from accidental laser reflections.


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closed as off-topic by Carl Witthoft, ACuriousMind, user36790, Gert, Kyle Kanos Nov 18 at 16:23

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Have you looked at laser safety goggles? See what they do for protecting against CO2 or similar IR sources. – Carl Witthoft Nov 18 at 13:45

1 Answer 1

CO2 lasers tend to be very high power. Often they will have 100 W in the beam. They can be much higher. Some will burn through safety goggles about as fast as you can blink.

Optical elements used with such lasers need to be designed for such power. When light strikes a coating, it is transmitted, reflected, or absorbed. Absorption must be kept down to a few tenths of a percent to avoid overheating. Reflectivity must also be low. Even so, light reflected from an antireflection coating on a concave surface can come to a focus and start a fire.

So I expect there isn't much demand.

That said, if you have a need, companies that manufacture such coatings can make custom coatings. There is no reason that a notch filter cannot be made. Look for companies that make lenses and other optical components for CO2 lasers.

Custom coatings tend to be expensive. They are sputtered in a vacuum chamber. For standard coating, the chamber can be filled with optics. For a custom coating the entire run is for your part.

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As a note, if you go the custom coating route, make sure to ask how much the price scales per piece. It usually doesn't cost much more to fill the entire chamber with parts. Sometimes you can get 10 parts for only ~10% more than the cost of a single part, because the coating run cost stays the same no matter how many parts are put in. Its just the material costs that increase. – tmwilson26 Nov 18 at 15:21

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