Laser collimation of a chromium beam

Abstract

We have studied laser collimation of a chromium atomic beam using a transverse polarization gradient cooling scheme. We present detailed measurements of the angular distribution of atoms on the beam axis, over a broad range of laser intensities and detunings, including those that produce significant excitation, and observe collimation angles as small as 0.16Ϯ0.01 mrad ͑50% quantile͒. We compare our results with existing calculations based on assumptions of steady-state conditions and low excited-state population. ͓S1050-2947͑97͒09402-X͔ PACS number͑s͒: 32.80.Pj, 42.50.VkHere ⌫ is the linewidth of the transition, ⌬ is the laser de-*Present address:

Fluorescence polarization imaging of Sisyphus cooling in an atomic beam

“…The fluorescence polarization imaging method was compared to measurements of the atomic beam divergence determined from the spatial derivative of the atomic beam profile [6]. A sharp knife edge was inserted to obscure half of the atomic beam immediately following the laser collimation, and the beam divergence of the cooled beam was obtained from the angular distribution function, …”

“…The cooling effect is typically characterized by measurement of the external motion of the atomic sample, such as the momentum distribution, density, or beam collimation [6]. Here we consider the polarization of the resonance fluorescence, in particular, the localization of atoms into subregions of the optical field and the evolution of the internal atomic states through optical pumping.…”

“…Sisyphus cooling can also be used to collimate a thermal atom beam [6], with applications in nanofabrication [7], frequency standards in atomic clocks [8], and focused ion beams [9][10][11].…”

Laser manipulation of iron for nanofabrication

“…We note that all these atoms possess a closed (or almost closed) optical transition that allows for efficient laser collimation. 7 In this letter we demonstrate atom-optical nanofabrication with iron. An iron atomic beam is deposited onto a glass-ceramic substrate through a one-dimensional laser SW tuned 200 MHz above the…”

“…In practice, laser cooling schemes are applied as they lead to extremely well-collimated atomic beams with no loss of flux. 7 It is this laser cooling requirement that has limited nanofabrication via atom optics to just a few atomic species with a suitable optical transition. So far, laserfocused nanofabrication was demonstrated only with sodium, 8 chromium, 3 aluminum 9 and ytterbium 10 in the direct deposition regime, and with cesium 11 via lithography with a self-assembled monolayer as the resist.…”