Figure 3
From: Fiber guiding at the Dirac frequency beyond photonic bandgaps
Guided modes in a triangular lattice photonic crystal fiber of germania glass. The fiber structure is shown in Figure 1a, where a=2.21 μm, ra=0.47a, R=1.9a, and εr=1.592. The modes were numerically calculated using the PWE method. The light-blue circles in the dark blue background give the positions of the hole−glass interfaces. (a–e) correspond to the red diamonds labeled 3a–3e in Figure 2b: (a) a gap mode (ωa/2πc= 1.432), (b) a mode at a frequency between the photonic band gap and the lower edge of the Dirac spectrum (ωa/2πc=1.601), (c) the Dirac mode (ωa/2πc=1.689), (d) a mode in the Dirac spectrum (ωa/2πc=1.761), and (e) a mode at a frequency higher than the upper edge of the Dirac spectrum (ωa/2πc=1.950). The electric-field pattern |E| is shown on the left, and the product r3/2|E| or r|E| on the x- or y-axis is shown on the right.
