# Optimum wavelength for ground-based laser weapons

In a futuristic setting where people are worried about enemy spacecraft doing things like dropping bombs from orbit, and are building ground-based lasers to shoot back,

Given that such weapons have the disadvantage of having to shoot up through atmosphere (putting them on high ground ~2 km helps a bit, but only a bit),

What is the optimum wavelength to minimize absorption and scattering by air (and preferably by clouds)? It's definitely going to be some way into the infrared, but what exact wavelength would be best?

• Maybe you will find this interesting gsp.humboldt.edu/olm_2016/Courses/GSP_216_Online/lesson2-1/… . Otherwise there are several wikipedia articles about such a topic. I think as it stands this question doesn't really display a lot of research effort. It's also not really about world building – Raditz_35 Apr 18 '18 at 11:15
• you can see the Sun outside. that's should give you a huge hint... – L.Dutch Apr 18 '18 at 11:35
• Have you read about military laser projects from the past? On some, wavelength was not classified. – Mołot Apr 18 '18 at 11:37

• What about that band around $10 \mu m$? Sure, absorption seems to be about 15%, but on the upside you probably have way less scattering. Is there any numerical estimate on how much scattering you get? – Alice Jul 4 '18 at 8:40