A method of fabricating a microstructure for an optical waveguide such as
a photonic bandgap fiber is provided. The method includes the steps of
assembling a stack of capillary tubes having substantially identical
dimensions, fusing and redrawing the stack into a preform having a
plurality of parallel holes of equal diameter, selecting a pattern of the
holes for etching in order to increase their diameter, and plugging the
unselected holes at one end of the preform against the flow of a
pressurized etching fluid. Such plugging of the unselected holes is
accomplished applying a layer of a gel-like sealant over the end of the
preform, and then pushing the sealant into the holes to form sealant
plugs in all of the holes. The sealant plugs are then removed from the
selected holes by punching the sealant plugs out of the selected holes.
The selected holes are then etched by conducting a pressurized flow of
etching fluid to the end of the preform such that etching fluid flows
only through the pattern of selected holes. The resulting preform is then
fused and drawn into an optical waveguide, where the pattern of etched
and unetched holes may form, for example, the microstructure for a
photonic bandgap optical fiber.