Explaining the Bloch-Siegert Shift - A Beginner's Guide

[Malamala]

Hello! Can someone explain to me or point me towards a basic explanation of the Bloch-Siegert shift (even the Wikipedia explanation is not clear to me)? Thank you!

 

[BillKet]

Hello! Can someone explain to me or point me towards a basic explanation of the Bloch-Siegert shift (even the Wikipedia explanation is not clear to me)? Thank you!

Anyone, please?

 

[A. Neumaier]

What is unclear in https://en.wikipedia.org/wiki/Bloch-Siegert_shift ?

 

[Malamala]

What is unclear in https://en.wikipedia.org/wiki/Bloch-Siegert_shift ?

So from what I understand, in RWA we ignore the fast rotating frequency and doing so we get the actual resonant frequency of the system $\omega_0$. If we account for the fast rotating term, we basically have 2 laser lights interacting with the system, and the fast rotating one is shifting the levels that the slow rotating one is seeing, such that the measured frequency is shifted from $\omega_0$. I am not sure I understand how they go from the rotating frame (where they get these shifts), to the lab frame (where we actually measure them). Are the shifts the same in both frames (actually there seem to be 3 frames involved in this analysis)? What confuses me even more is how can the shift be a constant in time ($\frac{1}{4}\frac{\Omega_0^2}{\omega_0}$), given that the field is time varying?