Characteristics Of Photonic Band Gap In One-dimensional Photonic Crystals

In this paper, the photonic band gap and the high reflection range of the one-dimensional periodic dielectric structures, structures with metal layers and non-periodic structures are studied theoretically.The particular expression of dispersion relations were deduced based on the traditional transfer matrix method. By using the expression, the relation between relative bandwidth and each optical parameter was analyzed. The results indicated that the relative bandwidth became wider when the ratio of two refractive indexes increased. According to the "parameter modulation method", the ratio of two optical thicknesses hardly affects the bandwidth when the discrepancy between the optical thicknesses is not too much. The numerical simulating shows the same result. The investigation of incidence angle shows that the relation between relative bandwidth and incidence angle differs in different polarizations.The transmission, reflection and absorption of light wave through one-dimensional metal-dielectric photonic crystals made of Si, Al and SiO₂ were numerical simulated. The results show that by inserting the Aluminum layers the rejection level is improved, the absorption of long wavelength is decreased and the high reflection bandwidth is broadened. Between the wavelength 400-1200nm, a high reflection range wider than Si/SiO₂ quarter-wave multi-layers was gained after inserting 30nm Aluminum layers.The variable thickness was introduced into periodic structures. The numerical investigation shows that the bandwidths of both the disorder and line graded dielectric structures are broadened compared to periodic photonic crystals. As in the metal-dielectric photonic crystals, line graded thicknesses increase the absorption and result in narrower band gap while the disordered thicknesses broaden the band gap.