The stack and draw process

The fabrication of high quality custom-designed PCF is central to the research of the Division. We use the "stack-and-draw" procedure, which relies on manual assembly of glass capillaries and rods into an appropriate preform stack whose structure corresponds approximately to the desired fibre structure. After inserting the preform stack into a glass tube and fusing during the drawing process, one obtains a microstructured preform or "cane". The final step in PCF fabrication involves drawing the cane into fibre with the desired dimensions, such as cladding-lattice pitch and the outer fiber diameter. By tuning process parameters such as temperature, preform feed rate and drawing speed, as well as the pressure inside the preform, the size of the air-holes and their regularity can be controlled. As for standard fibers, the fabricated PCF is coated with a polymer jacket for improved mechanical strength.

Steps in the fabrication of photonic crystal fibres. (1) 1 mm thick capillaries are drawn to precise dimensions and then (2) stacked to form the desired "preform". (3) The preform is fused together and drawn down in size to a "cane" (~1 mm in diameter). (4) In the final drawing step, the cane is drawn down to fibre and encased in a silica outer cladding.