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. - Highlights: • TiO₂/SiO₂ 1DPC has been fabricated using magnetron sputtering technique. • Experimental optical response is found good agreement with simulation results. • Wide omnidirectional photonic band in the visible spectrum has been achieved.