# Optimal laser wavelength for heating air

Lets say I want to heat air with laser,what wavelenght should I chose,ultraviolet,infrared or something in visible spectrum? To clarify,I want the laser beam to lose power and get converted to heat in shortest amount of distance possible. I am looking for maximum absorbtion, to convert the laser into heat.

When I think about it,two different wavelenght may produce equal heating of air,but the thing is one that have short range will produce heating that is more concentrated in space while other will heat air over longer distance so the energy will be spread over greater amount of air,I want that short range concetrated type heating so minimum quantity is heated to high as possible peak temperature.

• en.wikipedia.org/wiki/Atmosphere_of_Earth#Optical_properties – John Dvorak Jan 8 '17 at 19:57
• If it's moist air - definitely IR. Otherwise difficult exciting $N_2$, $O_2$ molecules by themselves. There are more efficient ways of heating air other than lasers. – docscience Jan 8 '17 at 20:33
• You may have better luck with phased array ultrasonics; acoustic frequencies modulated at a distance by one or more ultrasonic sources. How high of a temperature are you trying to heat the air to? – docscience Jan 8 '17 at 20:38
• the other gentleman who commented is saying "short wavelenght",you say IR which is long wavelenght,now I dont know who to believe – wav scientist Jan 8 '17 at 21:22
• @wavscientist: Both approaches make sense, but for different reasons. IR is the simple approach. UV isn't going to do much, until you hit non-linear effects (ionization). That requires much more engineering to work. Then again, how do you plan to avoid heating up your laser source? Even more engineering question, not so much physics theory. – MSalters Jan 9 '17 at 0:56