SNAP: fabrication of long coupled microresonator chains with sub-angstrom precision.

Based on the recently-introduced Surface Nanoscale Axial Photonics (SNAP) platform, we demonstrate a chain of 30 coupled SNAP microresonators spaced by 50 micron along an optical fiber, which is fabricated with the precision of 0.7 angstrom and a standard deviation of 0.12 angstrom in effective microresonator radius. To the best of our knowledge, this result surpasses those achieved in other super-low-loss photonic technologies developed to date by two orders of magnitude. The chain exhibits bandgaps in both the discrete and continuous spectrum in excellent agreement with theory. The developed method enables robust fabrication of SNAP devices with sub-angstrom precision.