Abstract
It has recently been shown that optical reflection gratings fabricated directly into an atom chip provide a simple and effective way to trap and cool substantial clouds of atoms (Nshii et al. in Nat Nanotechnol 8:321–324, 2013; McGilligan et al. in Opt Express 23(7):8948–8959, 2015). In this article, we describe how the gratings are designed and microfabricated and we characterise their optical properties, which determine their effectiveness as a cold atom source. We use simple scalar diffraction theory to understand how the morphology of the gratings determines the power in the diffracted beams.
Highlights
Atom chips [3, 4] are microfabricated devices [5] which control and manipulate ultracold atoms in a small, integrated package. Because they provide a convenient way to trap [6,7,8,9], guide [3, 10] and detect atoms [11], atom chips are becoming increasingly important for clocks [12, 13], Bose–Einstein condensates [14,15,16], matter wave interferometers [17,18,19,20] and quantum metrology [20]
Measurements on the three gratings of chip B gave P1/Pin = 0.381(2), 0.381(2) 0.380(2), showing a good level of reproducibility. This is due in part to better uniformity of the e-beam lithography, and, chip B operates with r = 0.46(5), which is very close to the maximum of the plot in Fig. 4c, where P1 is insensitive to variation of r
Optical reflection gratings fabricated on an atom chip offer a simple way to build a large, robust, integrated magnetooptical trap (MOT) for atoms [1]
Summary
Atom chips [3, 4] are microfabricated devices [5] which control and manipulate ultracold atoms in a small, integrated package. Thick wafers are available, days of etching are needed to make pyramids of mm size and additional polishing is required to achieve optical quality surfaces [8, 23, 24]. The gratings are fabricated on any standard substrate material and can readily be made on the centimetre scale This allows the MOT to capture up to 108 atoms above the surface of the chip, where they can be conveniently transferred to magnetic traps [3]. Because they only need a small depth of etching, the gratings preserve the 2D nature of the structure and sit comfortably with other elements on the chip.
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