Magneto-optical trap loading rate dependence on trap depth and vapor density

Abstract

We study the dependence of the particle loading rate of a rubidium vapor cell magneto-optic trap (MOT). Using a trap depth determination of the MOT that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state, we experimentally determine the MOT escape velocity and show that the loading rate scales with escape velocity to the fourth power, or, equivalently, with the square of the trap depth. We also demonstrate that the loading rate is directly proportional to the background rubidium density. We thus experimentally confirm the loading rate model used in the literature since the invention of the MOT. In addition to confirming this long-standing conjecture, we show that the loading rate dependence can be used to reliably infer the trap depth and to tune the relative depth of a MOT (i.e., capture and escape velocities) when the background density is held fixed. The measurements have allowed an experimental determination of the relationship between capture and escape velocities in our MOTs of v c 1.290.12v e .

Pump–probe and Four-wave Mixing Spectra Arising from Recoil-induced Resonance in an Operating Cesium Magneto-Optical Trap

“…This equation is widely used by other groups and the reliability has been verified. 27,28) Ignoring the effects of magnetic field and the Gaussian intensity profile of the laser beams, the radiation pressure force can be written as 25) F ¼ ħk 0 À 2…”

Precision engineering for ultra-cold atoms and space experiments

“…The polarimetry measurement was normalized with the input power (photodiode signal) to extract the probe-light optical rotation 76 . Care was taken to remove the photodiode offset before the normalization 77 . In order to reduce the noise in the estimation of the probe power, a moving average technique was implemented: a moving average window time of 2 ms was employed, which was sufficient to follow accurately the (low frequency) fluctuations in power and satisfy the low noise requirement described in section 5.9.2 (fractional power uncertainty < 10 −6 ).…”

“…5.26. 77 As mentioned in section 5.9.2, at each run, data recording started 100 ms before turning on the Faraday probe, allowing for the precise estimation (after averaging over all the runs) of the offsets. 78 Here, we concentrate on the part of the recorded data that contained the Faraday optical rotation (blue curve in Fig.…”

“…The first realization of a MOT was done in [74] and since then has become one of the cornerstones of many ultra cold atoms experiments [75]. One important advantage is that atoms can be loaded into the trap from room temperature vapor [76] and it's trap depth can extend even up to a few Kelvin [77].…”

Guided matter-wave interferometry

“…The first realization of a magneto-optical trap was done in the optical molasses setup by simply adding a spherical quadrupole field [12]. The trap depth of the MOT can extend even up to a few Kelvin [68], and atoms can be loaded in this trap from the room temperature vapor [69]. Fig.…”