Photonic band structure of nanoporous anodized aluminum oxide with radius-to-period ratio modulation

Photonic band structure and photonic band gap of nanoporous anodized aluminum oxide (np-AAO) based photonic crystals is numerically investigated in detail based on the plane-wave expansion method, with emphasis on the modulation of radius-to-period ratio of the cylindrical holes. This ratio is extremely convenient to be controlled experimentally, which is a unique feature of np-AAO. Transverse-electric and transverse-magnetic polarizations are considered due to the inherent optical anisotropy. Generally, a larger band gap (up to 10%) with wider wavelength range can be generated for TE polarization compared with TM polarization, considering the fairly low dielectric constant contrast.