Investigation of defect modes with Al2O3 and TiO2 in one-dimensional photonic crystals

One-dimensional photonic crystal (1D PC) filters with one defect layer are investigated at visible frequencies both theoretically and experimentally. 1D PC filters containing one Al2O3 or TiO2 defect layer are fabricated by pulsed laser deposition. The optical properties of the filters, including the transmittance and the resonance wavelength, are numerically calculated by using the transfer matrix method. Our results show that the defect layer with the lower refractive index is more suitable for the filters. Both blue- and red- shifts of the filter resonance are observed, depending on the thickness of the defect layer. We also find that the resonance may disappear as the number of periods in the filter increases (with the optical thickness of the defect layer fixed at 3/2 λ.