Flat-band localization and self-collimation of light in photonic crystals

• Published in: Scientific reports Vol. 9; no. 1; p. 2862
• Main Authors: Myoung, Nojoon, Park, Hee Chul, Ramachandran, Ajith, Lidorikis, Elefterios, Ryu, Jung-Wan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.02.2019; Nature Publishing Group
• Subjects: 639/624/399/1022; 639/766/400/1021; Crystals; Humanities and Social Sciences; Localization; multidisciplinary; Optical properties; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-39471-0

We investigate the optical properties of a photonic crystal (PC) composed of a quasi-one-dimensional flat-band lattice array through finite-difference time-domain simulations. The photonic bands contain flat bands (FBs) at specific frequencies, which correspond to compact localized states as a consequence of destructive interference. The FBs are shown to be nondispersive along the Г →  X line, prohibiting optical transmission with incident light in x direction. On the other hand, the photonic band for the FB frequency is found to be dispersive along the Г →  Y line, resulting in nonzero optical transmission. Such anisotropic optical response of the PC due to the FB localization of light in a single direction only results in a self-collimation of light propagation throughout the PC at the FB frequency.