Ultrawide Photonic Bandgap and Ultrastrong Photonic Localization Produced by Series of Periodic Networks

Abstract

AbstractA series of periodic networks is designed, in which all of the unit cells construct a series of fractal triangles, and their extraordinary optical characteristics for producing ultrawide photonic bandgap (PBG) and ultrastrong photonic localization are investigated. The results indicate that with increasing fractal generation, the number of equivalent triangular loops increases exponentially, and consequently the gap–midgap ratio of the PBG produced by the networks with the integer waveguide length ratio of 1:2 enlarges rapidly and tends to the limit at 200%. For the networks with the noninteger waveguide length ratio of (where ), an extremely narrow passband occurs in the middle of the wide PBG. Furthermore, the ultrastrong photonic localization is generated when the electromagnetic wave with the frequency of the all‐transmission peak in the ultranarrow passband propagates in the networks. This type of fractal triangular networks may have applications to design all‐optical devices, such as highly sensitive optical filters, highly sensitive all‐optical switches, and high‐performance photonic energy‐storage devices.