Demonstration of a MOT in a Sub-Millimeter Membrane Hole.

We present a demonstration of generating a cold-atom ensemble within a sub-millimeter diameter hole in a transparent membrane. The atom number inside this physical hole of diameter d = 400 um is about 10^5 times higher than the predicted value using the conventional d^6 scaling rule for the same physical hole on the optically opaque material. The atoms trapped by the membrane MOT are cooled down to 10 uK with sub-Doppler cooling. Such a device can be potentially coupled to the photonic/electronic integrated circuits that can be fabricated in the membrane device representing a step toward the atom trap integrated platform.