Second order correlation function for non ideal laser

[pumpkin]

Hi, it is known that second order correlation function (g²) is a constant( =1) for ideal laser or single frequency light sources. So, what is the second order correlation function for non ideal laser? Is it still a constant or something related to the coherence time of the laser?

 

[Cthugha]

For non-ideal laser the second-order correlation function at zero delay is typically larger than 1 (thermal light would show a value of 2) and decays down towards 1 with increased delaywith a time constant given by the coherence time of the light. The actual shape of the decay towards 1 depends on the reason why the laser is not ideal.