Micromachining structured optical fibers using focused ion beam milling
  A focused ion beam is used to mill side holes in air-silica structured fibres. By way of example, side holes are introduced in two types of air-structured fibres (1) a photonic crystal four-ring fibre and (2) a 6-hole single ring step index structured fibre. 
C. Martelli, P. Olivero, J. Canning, N. Groothoff, B. Gibson, S.   Huntington
cond-mat.mtrl-sci