Ultra-wide bandgap of gradient dielectric constant photonic crystal

A diamond-structured photonic crystal (PC) of gradient dielectric constant realized by combining alumina PC with two different solid loadings of alumina powder in the slurry was fabricated using the stereolithography (SL) and gel-casting process. The ultra-wide bandgap was experimentally confirmed by reflection and transmission measurements and simulated by the Finite Integration Technique (FIT). It was found that, the bandgap width of the PC with gradient dielectric constant increased remarkably in comparison with that of the normal alumina PC and reached 8 GHz, which was 117.6% of that of the alumina PC(60 vol.%). The maximum attenuation attained from the fabricated sample is-63.4 dB. The results indicate that the diamond-structured PC with gradient dielectric constant could effectively expand the bandgap width of the PC. The simulation result agreed well with the measurement result by FIT.