Understanding Waveform & Autocorrelation in Pulse Lasers

[Ted goldmund lee]

So, I was working on autocorrelation for my pulse laser system and I started to wonder what is the difference between single wave with 400nm of wavelength and two 800nm waves overlapped.
In the knowledge, I know of, is that wavelength is the length between two picks.

And when it is pulse laser, often we use co-linear autocorrelation to obtain time width of our pulse. When I do this, how accurately I overlap two beams it shows 800nm not 400nm but in my dumb head I can't help but think this should be 400nm.

I know it is not 400nm because I saw it, but I just want to know what is the main difference.

 

[mjc123]

If you overlap two 800 nm waves, exactly half a wavelength apart, you will get destructive interference and no intensity. You will not get a wave of wavelength 400 nm.

 

[Andy Resnick]

Summary: So, I was working on autocorrelation for my pulse laser system and I started to wonder what is the difference between single wave with 400nm of wavelength and two 800nm waves overlapped.
In the knowledge, I know of, is that wavelength is the length between two picks.

I'm confused- why do you associate a single wavelength with a laser pulse?