Finite Difference Time Domain Method (fdtd) Transmission Characteristics Of Photonic Crystal

The finite-difference time-domain(FDTD) technique receives growing attention in the area of electromagnetic simulation. It is based on a direct discretization of Maxwell' s equations in the time domain. It can simulate electromagnetic field distributions in structures of arbitrary geometry. Another advantage of FDTD is, that it provides results for a large range of frequencies in a single run by applying a pulsed start field and Fourier transforming the response. Decades of development and rapid growth in computer capability have built up a firm foundation for FDTD technique to be applied to many practical problems.In this paper, the Finite-Difference Time-domain method is applied to the computation of the transmission properties of 2D photonic crystals. The program code is written in Fortran both and VC++ . Because of the scaling properties of photonic crystals, a square lattice 2D photonic crystal array in the GHz microwave range is fabricated. Its transmission spectra is measured. The theoretical results coincide with that of the experiment.For a plane wave incidence, transmission and reflection spectra of photonic crystals are given. Field distributions of different frequencies (inside and outside the photonic band gap) in photonic crystals are also presented. The time-evolution of electromagnetic field distribution coupled between a cavity and a waveguide are obtained. The results indicate: Photonic crystals waveguide coupling follows the same regulation with conventional dielectric waveguide, further more: Photonic crystals waveguide directional coupler coupling coefficient is linear with the frequency. Simulation show: Different-wavelengths can be multi/demultiplexed by using photonic crystals directional couplers which are connected sequentially. In addition, Poynting vector in photonic crystals waveguide is gained.