Rubidium vapor cell with integrated Bragg reflectors for compact atomic MEMS

This paper reports on a method for improving the optical efficiency of micromachined reflectors integrated in rubidium vapor cells for application in atomic MEMS sensors. A hybrid bulk micromachining and multilayer PECVD thin film process is used to form the Bragg reflectors on angled sidewalls, which redirect laser light through the vapor cell and back toward the plane of the source with reduced optical power loss. Integrated thin film Bragg reflectors are shown to improve the reflectance of the micromachined surface by almost three times, resulting in an optical return efficiency of two paired dielectric reflectors that is as much as eight times higher then uncoated silicon reflectors. Absorption of the Rb87D1 absorption line at a wavelength of 795 nm in a 1 mm3mm3 vapor cell is demonstrated experimentally by use of two integrated thin film reflectors with a total optical return efficiency approaching 40%.