Differentiating surface plasmon-polariton waves and waveguide modes guided by interfaces with one-dimensional photonic crystals

One-dimensional photonic crystals (PCs) are made of planar layers of different materials with periodic arrangement. Such PCs can support multiple surface waves at their interfaces with homogeneous materials as well as multiple waveguide modes guided by individual constituent layers. The numerical results comparing multiple surface plasmon-polariton (SPP) waves and waveguide modes guided by a metal and a PC with only two layers in each period indicated that the periodic nonhomogeneity and the waveguide modes guided by the individual layers in the PC engender the multiplicity of SPP waves. For smaller value of the period of the PC, the coupling of the individual layers in the PC near the metal/PC interface gives rise to new SPP waves but the coupling reduces as the period increases and waveguide modes dominate. The differentiation between the waveguide modes and the surface waves is necessary to fully exploit the promise of photonic crystals in integrated optics.