All-angle self-collimation in two-dimensional square array photonic crystals based on index contrast tailoring

Abstract

A comprehensive study has been performed to achieve all-angle self-collimation in basic two-dimensional square array photonic crystals with cylindrical scatterers. Based on plane wave expansion and finite difference time domain analysis for both rod-and hole-type structures, we report on all-angle self-collimation (SC) in the first band of the structure, which results in loss suppression due to out-of-plane scatterings. A lower threshold for index contrast has been obtained to achieve all-angle SC, which offers more design flexibility regarding structural parameters. Furthermore, it has been shown that a minimum and maximum coupling efficiency enhancement of ∼40% and 80% can be achieved for the proposed structure, respectively, by introducing a row of scatterers with proper radius at the input and the output air/photonic crystal interfaces. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms Optical Engineering 037111-2 March 2015 • Vol. 54(3) Noori, Soroosh, and Baghban: All-angle self-collimation in two-dimensional square array photonic crystals. . . Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms Mina Noori received her BS and MS degrees in electronics engineering (optical integrated circuits) from University of Tabriz, Iran, in 2010 and 2012, respectively. She is currently working toward her PhD degree at Shahid Chamran University, Ahvaz, Iran, and her current research interest includes photonic crystal devices and structures. Mohammad Soroosh received his MS and PhD degrees in electronics engineering from Tarbiat Modares University, Tehran,

Self‐Collimation in Photonic Crystals: Applications and Opportunities

“…As a highly qualified platform for the development of devices for optical integration, self‐collimating PCs must provide broadband and wide‐angle operation for both TE and TM polarizations . In recent years, a great number of studies have been devoted to broaden the frequency range for SC phenomena, expand the incident angle range, achieve PISC, and reduce the reflections from the interfaces …”

“…In this case, the incident light at any incident angle can be collimated to a certain direction inside the PC. As the second condition, the PC must present an open flat EFC . However, in conventional PCs, the incident angle for SC is limited to values smaller than 90°.…”

“…Schematic illustration of a) EFC for limited angle SC, and all‐angle SC achieved by b) long flat and c) open flat EFCs. Reproduced with permission . 2015, SPIE.…”

“…The possibility of achieving all‐angle SC in the first band of a 2D square array of cylindrical scatterers was studied in 2015 . The hole and rod‐type structures have been considered for various index contrasts and radius values.…”

“…The intentional use of the first band for the aim of SC rather than the second band can suppress the out‐of‐plane scattering and introduces a threshold for index contrast which results in all‐angle SC. The difference between the study presented in and relies on the fact that a high degree of freedom is obtained considering the condition required for all‐angle SC by presenting the threshold index contrast instead of using ultra‐high‐refractive‐index materials. Additionally, the possibility of attaining all‐angle SC in a basic square array without any need to further break the structural symmetry or complicate the PC lattice is revealed compared with previous reports.…”