Preparation of photonic crystals made of air pores in anodic alumina

16 Aug 2007

Researchers from China describe the fabrication of large-area photonic crystals with strong photonic bandgaps in the visible region.

The researchers fabricated the photonic crystals (PCs) by electrochemical oxidation of aluminum foil while periodically adjusting the anodizing cell voltage, and then enlarging the pores by chemical etching. The team then confirmed the presence of a photonic band gap in the optical spectrum using optical photographs and transmission spectra (Nanotechnology 18 365601).

The team found that the color of the sample and the diffraction peak position in the transmission spectra can be easily adjusted by tailoring the chemical etching process. The size of air pores in the membrane can be altered by adjusting the chemical etching time, temperature and concentration of the acid solution, and the researchers demonstrated that the volume fraction of air nanopores in the photonic crystals can be reliably controlled between 30% and 80%, and the diameter can be controlled from 40 to 80 nm.

The method described by the team provides a possible approach to producing large-area optical photonic crystals cheaply and rapidly. The fabrication method offers additional advantages, since the ability to tune the rejected wavelength by simply adjusting the chemical etching time means that this kind of anodic membrane can be used directly in fabricating diffractive optical components, such as narrow-band filters.