Introduction

Photonic crystals (PhCs) are a novel class of optical media represented by natural or artificial structures with periodic modulation of the refractive index. Depending on the geometry of the structure, PhCs can be divided into three broad categories, namely, one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) structures. Here, the periodicity of the refractive index (i.e. dielectric constant) gives rise to photonic band gaps (PBG), forbidden energy bands for photons. Basically, in case of 1D PBG structure, the periodicity is within the structure along 1D only and is considered in terms of Bragg gratings[1].

Villar et al.[2] have proposed a multiple wavelength optical filter for 1D PhC with defects. Further, L. Scolari et al.[3] have proposed a tunable bandpass filter based on PhC fiber filled with multiple liquid crystals. It is also seen that[4], photonic crystal polarization filter is a type of filter which uses the band gap property of the photonic crystal to control the polarization state of the light signal. Xi-Hua Zou et al.[5] proposed a 1D PhC based on multichannel filters using binary phase-only sampling approach. Some studies on Fourier transform theory has also been done on PhC for filtering action[6]. Qiu and Jaskorzynska[7] have proposed a model design for a channel drop filter in a two-dimensional triangular PhC.

In this chapter, an optical filter based on the tunability of its excitation pulse for differentmaterials such as glass, GaAs, ebonite and titanium dioxide is proposed using finite difference time domain (FDTD) method with varying layer thickness and mesh elements.

This chapter has been organized in followingmanner: Design and analysis, result and discussion and conclusion.

Design and Analysis

Photonic crystal structure

A photonic crystal is amicrostructure that exhibits frequency intervalswithinwhich electromagnetic waves propagate irrespective of their propagation direction. The basic function of PhCs is that it controls the recombination of an electron−hole pair in a semiconductor during spontaneous emission, such that when optical transition occurs within this structure, band gap overlapping takes place.

FDTD method

Various types of computational methods have been adopted to analyze photonic crystal structure. They are: plane wave expansion (PWE) method, transfer matrix method, Green's function method and finite difference time domain method. However, in this study the FDTD method based on Yee's algorithm[8] is employed to observe the 1D-PCS, because the computational time and memory requirements are reduced.