Figure 6

Dimpling procedure. Schematics and microscope images illustrating the tapered fiber dimpling procedure. All scale bars are 125 μm. a) The fiber is detensioned slightly (by about 10 μm) by moving the fiber mounts inward, producing a small protrusion at the fiber’s thinnest point. The fiber mold is then adjusted such that it is aligned with this section of the fiber. b) The fiber mold is raised approximately 5 mm allowing the tapered fiber to wrap around it. The fiber mounts are gradually moved inwards as to prevent the fiber from breaking, while still maintaining tension on the fiber mold. c) An inverted hydrogen torch with a large flame (using HT series torch tip) is approached by hand, annealing the tapered fiber into a dimpled shape. d) The fiber mold is lowered while the fiber mounts are moved outwards to restore tension to the newly formed dimple. The dimple is gently removed from the fiber mold by flowing low pressure hydrogen gas from below. e) Optical microscope image of the resulting dimpled tapered fiber using this procedure. f) Plot indicating transmission (normalized to the pre-dimpled value) through the tapered fiber before and after dimpling. Losses induced by introducing the dimple to the fiber are around 8%.