Computation of photonic bandgap in two-dimensional periodic triangular lattice for bandpass filter design

Complete photonic bandgap is formed in two-dimensional photonic crystal with triangular geometry under TE mode of propagation. Maxwell's equations are solved using plane wave expansion method and eigen equations for TE and TM modes are obtained using appropriate boundary conditions. Structure is realized by inserting cylindrical rods in triangular lattice. Results reveal that magnitude of bandgap and mid-band frequency depends on refractive index difference of the two materials, and also on lattice filling factor. Result is compared with that obtained for rectangular lattice, and better control on tunability of the properties is exhibited by triangular geometry. Simulated findings will play key role in designing photonic bandpass filter for photonic integrated circuit.