Temperature and wall coating dependence of alkali vapor transport speed in micron-scale capillaries

Abstract

The impact of storage temperature and wall coatings on alkali vapor transport through micron-scale glass capillaries is analyzed. Glass microbore tubing, chromatography vials, and copper tubing are assembled into closed atomic spectroscopy units with varying capillary lengths and inner diameters. Such devices serve as valuable test models for integrated atomic spectroscopy platforms that rely on hollow-core optical waveguides for chip-scale implementation of quantum coherence phenomena such as slow and stopped light. The inside surface of the systems are coated with dimethyldichlorosilane (DMDCS) after which the system is loaded with rubidium vapor and hermetically sealed. The loaded units are stored in a tube furnace at elevated temperatures and tested daily for absorption over several weeks. Both a wall coating of DMDCS and higher storage temperature increases the transport speed of Rb vapor. The limits and implications of these results are discussed and compared to an expected theoretical model. Suggestions for increasing transport speed are given.