Air-guiding photonic bandgap fiber with improved triangular air-silica   photonic crystal cladding
  We introduce a small-core air-guiding photonic crystal fiber whose cladding is made of improved air-silica photonic crystal with non-circular air holes placed in triangular lattice. The fiber achieves un-disturbed bandgap guidance over 350nm wavelength range. 
M. Yan, and P. Shum