Omnidirectional bandgap in Cantor dielectric multilayers

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• 作者：Francesco Chiadini ; Vincenzo Fiumara ; Ilaria Gallina ; Antonio Scaglione
• 关键词：Dielectric multilayers ; Cantor fractals ; Omnidirectional bandgap
• 刊名：Optics Communications
• 出版年：2009
• 出版时间：1 October 2009
• 年：2009
• 卷：282
• 期：19
• 页码：4009-4013
• 全文大小：766 K

文摘

Analysis of the transmission spectrum of Cantor dielectric multilayers for obliquely incident plane wave shows that the main bandgap shifts towards higher frequencies, substantially retaining its shape, as the incidence angle increases for both s- and p-polarization of the impinging wave. For suitable refractive index values of the two constituent materials a range of frequencies can be found where transmission of the incident wave is almost completely forbidden at any angle of incidence. This omnidirectional bandgap can be found also for lossy media. In this case the stop-band widens as the tangent loss increases, while the depth of the stop-band does not change significantly. Comparison with the periodic quarter-wave stack shows that the Cantor multilayer exhibits a narrower omnidirectional bandgap with transmissivity values that are about one order of magnitude lower.