Ultraviolet light-induced atom desorption for large rubidium and potassium magneto-optical traps

We show that light-induced atom desorption (LIAD) can be used as a flexible atomic source for large ${}^{87}\mathrm{Rb}$ and ${}^{40}\mathrm{K}$ magneto-optical traps. The use of LIAD at short wavelengths allows for fast switching of the desired vapor pressure and permits experiments with long trapping and coherence times. The wavelength dependence of the LIAD effect for both species was explored in a range from $630\text{to}253\mathrm{nm}$ in an uncoated quartz cell and a stainless steel chamber. Only a few $\mathrm{mW}∕{\mathrm{cm}}^2$ of near-UV light produce partial pressures that are high enough to saturate a magneto-optical trap at $3.5\times {10}^9$ ${}^{87}\mathrm{Rb}$ atoms or $7\times {10}^7$ ${}^{40}\mathrm{K}$ atoms. Loading rates as high as $1.2\times {10}^9$ ${}^{87}\mathrm{Rb}$ atoms/s and $8\times {10}^7$ ${}^{40}\mathrm{K}$ atoms/s were achieved without the use of a secondary atom source. After the desorption light is turned off, the pressure quickly decays back to equilibrium with a time constant as short as $200\mu \mathrm{s}$, allowing for long trapping lifetimes after the MOT loading phase.

Figure 1

Vacuum system of the experimental apparatus. The positions of the dispensers and the LIAD light are indicated.

Figure 2

${}^{87}\mathrm{Rb}$ atom number as a function of the MOT loading time for desorption light at various wavelengths.

Figure 3

Maximum atom number in the MOT versus desorption light wavelength, for ${}^{87}\mathrm{Rb}$ (solid dots) and ${}^{40}\mathrm{K}$ (open circles).

Figure 4

${}^{87}\mathrm{Rb}$ (solid symbols) and ${}^{40}\mathrm{K}$ (open circles) loading rates versus wave number of the desorption light. The solid squares for ${}^{87}\mathrm{Rb}$ represent rescaled data (see text).

Figure 5

${}^{87}\mathrm{Rb}$ (solid symbols) and ${}^{40}\mathrm{K}$ (open circles) atom numbers (top) and loading rates (bottom) versus desorption light intensity. The model which was used to fit the data will be evaluated in future work.

Figure 6

${}^{87}\mathrm{Rb}$ loading rate as a function of the delay after the desorption light was turned off.

Figure 7

${}^{87}\mathrm{Rb}$ loading rate versus wave number of the desorption light in a stainless steel chamber (solid dots) and a quartz cell (open circles).