Resonance Fluorescence

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Definition

Effect that occurs when an atom is subject to an electromagnetic field whose frequency is near the atom's resonant frequency. Due to the nonlinear nature of the atom, the behavior of the system can be non-trivial. For example, the incoherent fluorescence spectrum (at sufficiently high intensity) is not a single Lorentzian peak, as one might expect, but rather a three-peak structure (often referred to as the Mollow triplet).

Equations

The master equation for resonance fluorescence can be written as (see Carmichael reference below)

$\dot{\rho}=\frac{1}{i\hbar}[\mathcal{H},\rho]+ i(\Omega/2)[e^{-i{\omega_{A}}t}\sigma_{+}+e^{i{\omega_{A}}t}\sigma_{-},\rho]+ \gamma/2(2\sigma_{-}\rho\sigma_{+}-\sigma_{+}\sigma_{-}\rho-\rho\sigma_{+}\sigma_{-})$

where

$\mathcal{H}=\hbar\omega_{A}\sigma_{z}$

is the atomic Hamiltonian, and the $σ$ operators are the 2x2 Paul spin matrices.

This master equation is derived assuming the standard Born approximation and Markoff approximation, and assumes a classical driving field that is left undepleted by the interaction.