Author/Authors :
Gharaati, Abdolrasoul Physics Department, Payame Noor University, Tehran, Iran , Miri, Nasrin Physics Department, Payame Noor University, Tehran, Iran , Zareian, Zahra Physics Department, Payame Noor University, Tehran, Iran
Abstract :
In this paper, we study two different Graded Index (GRIN) photonic
crystal (PC) structures which are named as structure type I and type II. The PC
structures are made of the square rod in an air background. To design a GRIN
PC structure the lattice constant has been altered in the direction transverse to
propagation. We investigated focusing effect and waveguiding behavior of
electromagnetic waves propagating throughout the GRIN structures. Wide
incident beam with a Gaussian profile is illuminated to the both GRIN
structures. In the case of structure type I, the incident wave bend toward the
central part of the structure and after getting out of it focuses on the narrow
area. The designed structure shows the strong focusing effect and increase
normalized intensity and decreases the width of the outgoing wave. In the case
of structure type II, the incoming beam after traveling short distance becomes
distracted to the central part and remains confine in the middle of the structure.
The exiting wave can be coupled to a photonic crystal waveguide. Plane wave
expansion method has been used for analyzing dispersion relation. Propagation
of electromagnetic wave within the graded structure has been simulated using
finite-difference time-domain method.
Keywords :
photonic crystals , graded index , effective refractive index , plane wave expansion
