Recently physicists have managed to build "attosecond lasers", lasers
which emit pulses 10-18 seconds long, interrupted by much longer periods of darkness (at least 10-14 seconds). Before them, lasers emitting
femtosecond (10-15 seconds) pulses have been around. Assuming they
produce visible light, what colour is it?
A pulse that goes on and then off is a square wave. A Fourier transform of this is an infinite sum of sine waves. The largest component of this is a sine wave whose period is double the length of the pulse.
So I think the key wavelength would be 600 nm (red light), along with harmonics of decreasing intensity and shorter wavelengths.
Posted by Larry
on 2006-10-06 18:04:03