Design of 7 and 19 cells core air-guiding photonic crystal fibers for low-loss, wide bandwidth and dispersion controlled operation.

We study the modal properties of feasible hollow-core photonic bandgap fibers (HC-PBGFs) with cores formed by omitting either 7 or 19 central unit-cells. Firstly, we analyze fibers with thin core surrounds and demonstrate that even for large cores the proposed structures are optimum for broad-band transmission. We compare these optimized structures with fibers which incorporate antiresonant core surrounds which are known to have low-loss. Trade-offs between loss and useful bandwidth are presented. Finally, we study the effects that small modifications to the core surround have on the fiber's group velocity dispersion, showing the possibility of engineering the dispersion in hollow-core photonic bandgap fibers.