Fourier transform limited photons?

[Baggio]

Hi,

What is meant when they say photons are Fourier transform limited?


Thanks

 

[lalbatros]

references and quotations needed

 

[Baggio]

Ok sorry about that!

I'm basically just doing some quantum optics experiments for example this paper by Charles Santori:

http://www.nature.com/nature/journal/v419/n6907/abs/nature01086.html

(see attachment as well)

Which refers to photons emitted from a quantum dot. It is said that when there is no pure dephasing that the ratio of 2*(decay time)/(coherence time) = 1 and this means the photons are time-bandwidth or Fourier Transform limited. And apparently this means that your single photons are indistinguishable. After spending hours on google it seams that Transform limited photons are used in spectroscopy in other fields as well..

I just want to know physically and mathematically what a FT limited photon is.

It is also mentioned here

http://en.wikipedia.org/wiki/Ultrashort_pulse

 

[lalbatros]

Probably a good reference:

http://www.ull.rdg.ac.uk/documents/ULL_Antoncini.pdf

 

[Baggio]

Thanks looks promising!

 

[Baggio]

Hmm something still confuses me. It says there that transforrm limited photons have a broad spectrum. But if the spectrum is broad how is the light from the laser coherent? Wouldn't that mean that the laser emits at a broad range of wavelengths?

 

[lalbatros]

The light loses coherence indeed, but how much ?
The loss is minimal for a transform limited, I guess.
And still stimulated emission is involved.
And if coherence is reduced, your gain the impact of the pulse ...