High vacuum compatible fiber feedthrough for hot alkali vapor cells

We demonstrate a method to produce vacuum-tight, metal-free, bakeable, and alkali-compatible feedthroughs for optical fibers. The manufacturing process mainly relies on encasing fibers made of fused silica with glass materials with lower melting points by heating. We analyze the vacuum and optical performance of the devices by various methods such as helium leak checks and review several spectroscopic schemes, including electromagnetically induced transparency involving Rydberg states.