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.
Best Answer
As you need to heat air to high temperature anyway, maybe you should consider a very high-power (pulse) laser that induces breakdown in air (https://www.rp-photonics.com/laser_induced_breakdown.html ); after the breakdown, air will be ionized and will absorb more power. Ideally, you should choose shorter-wavelength laser to be able to better focus the beam, but it is often harder to get high power at shorter wavelength. There are several processes that need to be taken into account: when the air ionization is so high that the plasma frequency exceeds the radiation frequency, the plasma becomes opaque for the radiation; heated air expands, which causes decrease of temperature; some other nonlinear effects, such as self-focusing, can be significant as well.