ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 2, April 2012 ` 161 All Rights Reserved © 2012 IJARCSEE Abstract— one dimensional photonic crystal is the simplest possible type of the photonic crystals. The investigation of photonic structures by mathematical and a simulation method is highly important. At optical frequencies the optical density inside a photonic crystal varies periodically, they have the property to strongly affect the propagation of light waves at these optical frequencies. In the present work, band gap has been computed for a 1D photonic crystal. Both Plane Wave Expansion (PWE) and Finite-Difference-time-Domain (FDTD) methods are widely used for band gap computation of photonic crystals. Due to its advantage over PWE method, we have used FDTD method for computation of band gap for 1D photonic crystal. Index Terms— Band Gap, Finite-Difference-time-Domain, Plane Wave Expansion. I. INTRODUCTION Nanotechnology is a key technology of the 21st century. It investigates very small structures of the size of a few nanometers up to several 100 nanometers. Thus, these structures are often smaller then the wave length of light. Photonic crystals are an important class of physical structures investigated in nanotechnology [1]. The need for photonic crystals is often overshadowed in the public eye by the amazing benefits of fiber optic wires. True fiber optic wires, as well as plastic ones, are only able to bend to a small extent before either signal loss or cable fracture set in. Additionally, fiber optic cables acquire significant signal loss over long distances, and the signal must be strengthened by repeaters along the cable or by transmitter in order to be detectable by the receiver. Photonic crystals eliminate this problem, experiencing very little signal loss compared to the best fiber optic wires we have today [2]. Photonic crystals are typically ―honeycomb‖ structures made of silicon. They can be made into three different kinds of categories depending on what they will be used for: one-dimensional (1D), two-dimensional (2D), and three- dimensional (3D) builds. Examples of 1D, 2D and 3D Photonic crystals are shown in Figure 1. One-dimensional photonic crystals are made of layers of material stacked together with miniscule spaces between them to serve as Manuscript received April, 2012. Swarnjeet kaur, University College of Engineering, Punjabi University Patiala, Patiala, India, 9988237658. Deepak Saini, University College of Engineering, Punjabi University, Patiala, India, 9417401694. Amandeep Sappal, University College of Engineering, Punjabi University, Patiala, India, 9814357652. canals for light to pass through. The material serves as a buffer to keep the light from escaping. Figure 1: Examples of (a) 1D Photonic crystal (b) 2D Photonic crystal (c) 3D Photonic crystal Example of 1D Photonic crystal is Bragg grating, which is widely used as a distributed reflector in vertical cavity surface emitting lasers. One-dimensional crystals only allow light to propagate in a straight line, limiting their applications. However, two and three-dimensional photonic crystals have enormous potential in upcoming technologies. 2D Photonic crystal can have comparatively large variety of configurations, because it possesses periodicity of the permittivity along two directions, while in the third direction the medium is uniform. A good example of the 2D Photonic crystal is porous silicon with periodically arranged pores, which is represented by the silicon substrate with etched holes. There were also given results of band structure computation for the Photonic crystal with diamond lattice made of dielectric spheres placed in air where they found the complete Photonic band gap between the second and third bands. In 1992, H.S. Sozuer and J.W. Haus [6] computed the band structure of the Photonic crystal with inverted FCC lattice (also known as inverted opal). The term inverted opal means that instead of dielectric spheres placed in air, the inverted FCC lattice consists of a number of spherical cavities separated by baffles with higher refractive index. It appeared that such a Photonic crystal has complete Photonic band gap at relatively high refractive index of material. Investigated inverted opal had complete Photonic band gap between the eighth and ninth bands. The appearance of the complete Photonic band gap inside the Photonic crystal with inverted FCC lattice attracts a special interest, because today inverted artificial opals provide possibility of mass photonic crystal production. Band Gap Simulations of 1-Dimensional Photonic Crystal Swarnjeet Kaur, Deepak Saini, Amandeep Sappal