Study On EM Properties Of Photonic Crystal And Design Of Large Band-gap Structure

A photonic crystal is an artificial structure which has a periodic arrangement of dielectric or metallic materials. It is so-called "photon-semiconductor". In the past decade, it has become a new fast-developing research field due to its unique properties and many potential applications.As the structure of a photonic crystal is complex, it is relatively hard to analyze a photonic crystal in an explicit analytical way. People usually analyze a photonic crystal through numerical simulations. So numerical methods are the main clew in this paper.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 a pulsed start field and Fourier transforming the response. In this paper, the material of photonic crystal is supposed to be idealization and the FDTD equations for photonic crystal is educed. The electromagnetic nature of line-defect in photonic crystal was analyzed by FDTD method. The result shows that the special wave can propagate in the line-defect through sharp corners with low energy loss, which make the electromagnetic wave circuitry are easily integrated. Then the electromagnetic coupling from line-defect- to cavity in photonic crystals was analyzed and a high efficiency frequency-dropping model is designed.The method of transfer matrixs is relatively easy but very practical. It is mainly used to calculate the photonic band-gap (PBG) of one- dimensional photonic crystal. For many applications of photonic crystals, it is essential to design structures with large band gaps. In this paper, a new definition is given which is called" composite-photonic-crystal. It is made up of tow kinds of photonic crystal with different parameters. A one-dimensional composite-photonic-crystal and a two-dimensional composite-photonic-crystal are designed. Using transfer matrixs method and FDTD method, the photonic band gaps of composite-photonic-crystal were calculated. The result shows that the band gaps are obviously wider than that of both composite photonic crystals at near infrared wave.Among several theoretical methods proposed for photonic crystals, the plane wave expansion method (PWM) is the one that was proposed first and is used most commonly. However, it has disadvantage of slow convergence. In the last chapter, we use the plane-wave expansion method to study the absolute band gap of two-dimensional photonic crystal. We find the best parameters of photonic crystal for absolute band gap.The piecewise linear current density recursive convolution finite-difference time-domain (PLCDRC-FDTD) has high speed and efficiency, which is used to simulate the plasma photonic crystal in this paper. The dependence of EBGs on the plasma frequency, the collision frequency is investigated.In conclusion, the work in the present thesis is devoted to numerical methods, designing new structures large photonic band-gap or absolute band gap and application of new materials. Much progress has been obtained in each of the above-mentioned aspects.