A hollow-core waveguide structure for on-chip atomic spectroscopy is presented. The devices are based on Anti-Resonant Reflecting Optical Waveguides and may be used for a wide variety of applications which rely on the interaction of light with gases and vapors. The designs presented here feature short delivery paths of the atomic vapor into the hollow waveguide. They also have excellent environmental stability by incorporating buried solid-core waveguides to deliver light to the hollow cores. Completed chips were packaged with an Rb source and the F = 3 ≥ F′ = 2, 3, 4 transitions of the D2 line in 85Rb were monitored for optical absorption. Maximum absorption peak depths of 9% were measured.
Impedance spectroscopy in the radio frequency range from 100 MHz to 20 GHz can reveal the dielectric relaxations of biological and chemical solutions. S-parameters for a coplanar waveguide are derived. To perform these measurements, a coplanar waveguide device was fabricated on a conventional FR-4 substrate for fluid interrogation. The microfluidic channel was formed by milling conventional waveguides and laser-cutting channels in the dielectric substrate. Measurements using this device were performed on standards: deionized water, isopropyl alcohol, and air. These measurements were compared to those taken with a conventional dielectric probe. The results demonstrate the ability of the fabricated device to extract varying transmission parameters due to changing sample properties.
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.
This section is intended for the publication of (1) brief reports which do not require the formal structure of regular journal articles, and (2) comments on items previously published in the journal.
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