Omnidirectional photonic band gap in magnetron sputtered TiO2/SiO2 one dimensional photonic crystal

One dimensional photonic crystal (1DPC) of TiO2/SiO2 multilayer has been fabricated by sequential asymmetric bipolar pulsed dc magnetron sputtering of TiO2 and radio frequency magnetron sputtering of SiO2 to achieve wide omnidirectional photonic band in the visible region. The microstructure and optical response of the TiO2/SiO2 photonic crystal have been characterized by atomic force microscopy, scanning electron microscopy and spectrophotometry respectively. The surface of the photonic crystal is very smooth having surface roughness of 2.6 nm. Reflection and transmission spectra have been measured in the wavelength range 300 to 1000 nm for both transverse electric and transverse magnetic waves. Wide high reflection photonic band gap (∆ λ = 245 nm) in the visible and near infrared regions (592-837 nm) at normal incidence has been achieved. The measured photonic band gap (PBG) is found well matching with the calculated photonic band gap of an infinite 1DPC. The experimentally observed omnidirectional photonic band 592-668 nm (∆ λ = 76 nm) in the visible region with band to mid-band ratio ∆ λ/λ = 12% for reflectivity R > 99% over the incident angle range of 0°-70° is found almost matching with the calculated omnidirectional PBG. The omnidirectional reflection band is found much wider as compared to the values reported in literature so far in the visible region for TiO2/SiO2 periodic photonic crystal.