One-dimensional alumina photonic crystals with defect modes were successfully fabricated through inserting a constant voltage waveform into the periodic voltage signals. The trans-mission spectra show that the thickness of defects plays a key role in determining the trans-mittance of defect modes. When the thickness was ？180 nm, an obvious defect mode with the high transmittance of 55% and a narrow full width at half maximum of 18 nm was observed in the original photonic band gaps. The defect mode shifted linearly with the increasing of refractive index of the analytes infiltrated into pores, indicating its potential application in chemical sensing or bio-sensing.
