Progress towards chip-scale transverse laser cooling of thermal atomic beams

We present progress toward on-chip laser cooling of thermal rubidium atomic beams in an integrated platform using microfabricated collimators and MEMS mirrors. An array of etched thin silicon microcapillaries are attached to a rubidium reservoir containing a dispenser source. The photolithographically patterned array collimates and directs thermal atoms to the downstream cooling region with pinpoint accuracy. Micromirrors at the cooling region maneuver laser beams to form a strong standing wave, a stimulated blue molasses, that can reduce the transverse velocity spread to the cm/s range within a sub-centimeter travel distance. We have fabricated collimators and micromirrors, and performed stringent tests of the resistance of the latter to alkali deposition by directly spraying rubidium atoms emitted from dispensers. Our study shows that a dielectric coating layer effectively protects the gold mirrors from alkali attack compared with non-coated mirrors, as revealed by scanning electron micrograph (SEM) inspections on the test samples. The robustness of our micromirrors embedded with the beam source guarantees its reliability for long-term operation. This on-chip hybrid of passive and active collimation paves the way towards a high-brightness atomic beam source that can find its applications in making compact atomic instruments.