The optical responses of one-dimensional photonic crystals based on the transparent Ag‐anodic aluminum oxide composites with super low-refractive index

The super low refractive index of less than 1 is obtained through adjusting the deposition time of nano-metal Ag in Ag-anodic aluminum oxide (Ag-AAO) composite films. It is very interesting that the Ag-AAO composite films with super low refractive index are still transparent. Based on the results, the Ag-AAO composite films and titanium dioxide (TiO2) films were used to assemble 1D TiO2/Ag-AAO photonic crystal (PC) structure and its optical responses were simulated in the 500–2500 nm range by using the finite difference time domain method. It is found that the increase of Ag-AAO layer thickness makes the photonic band gap (PBG) become broad greatly, but has few effects on the blue edge of the PBG, which is different from the effect of TiO2 layers. It is more important that a broad omnidirectional PBG can be easily obtained from the simple 1D TiO2/Ag-AAO photonic crystal structure through the modulation of both the TiO2 and Ag-AAO layer thicknesses. Furthermore, the absorption of 1D TiO2/Ag-AAO PC structure at the PBG edges is very strong due to the photon localization in Ag-AAO layer. The different roles of Ag-AAO layer in the above mentioned 1D PC structure are mainly attributed to the different transmission process of optical pulse in Ag-AAO layer.

► Transparent anodic aluminum oxide (Ag-AAO) film with super low refractive index.
► The Ag-AAO film is used to assemble one dimensional photonic crystal (1D PC).
► The 1D TiO2/Ag-AAO PC has a broad omnidirectional photonic band gap (PBG).
► The Ag-AAO layer has different effect on the PBG from TiO2 layer in the 1D PC.
► The Ag-AAO layer has strong photon localization at the PBG edges in the 1D PC.