Single-Photon Atomic Cooling - Raizen Lab - The University of ...
Single-Photon Atomic Cooling - Raizen Lab - The University of ...
Single-Photon Atomic Cooling - Raizen Lab - The University of ...
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could potentially have undergone the single-photon cooling process thereby<br />
reducing the transfer efficiency. <strong>The</strong>refore, the intensity and detuning must be<br />
set strategically to maximize the efficiency <strong>of</strong> the transfer process. One may<br />
wonder why higher transfer efficiencies occur at larger frequency detunings.<br />
We believe that this can be understood by comparing the scattering rate in<br />
the depopulation beam to the rate in the magnetic trap due to scattered light.<br />
<strong>The</strong> rate at which atoms scatter near resonant light is found from Eq. 2.73 by<br />
multiplying ρ22 by the excited state decay rate. <strong>The</strong> result is<br />
Srate =<br />
s0Γ/2<br />
1 + s0 + 4(∆/Γ) 2,<br />
(4.1)<br />
where s0 ≡ I/Isat is the saturation parameter, Γ is the excited state decay rate,<br />
and ∆ is the detuning from the resonance transition frequency. This equation<br />
shows that the scattering rate is not a linear function <strong>of</strong> beam intensity, rather<br />
the scattering rate begins to saturate when atoms spend a significant fraction <strong>of</strong><br />
their time in the excited state. With this formula in mind, we are in a position<br />
to compare the scattering rate at the depopulation beam focus (high saturation<br />
parameter) with the rate in the magnetic trap (low saturation parameter) as a<br />
function <strong>of</strong> depopulation beam detuning from resonance. We begin by writing<br />
the scattering rate in the depopulation beam as<br />
Sdepop =<br />
s0Γ/2<br />
1 + s0 + 4(∆/Γ) 2.<br />
(4.2)<br />
While the amount <strong>of</strong> light scattered into the magnetic trap is unknown, it must<br />
be proportional to the intensity <strong>of</strong> the depopulation beam. Since s0 ≡ I/Isat<br />
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