Widening Of PBG In 1D Photonic Crystal And Design Of Filter

Photonic crystal is a new type of artificial microstructure material with characteristic of photonic band gap (PBG) structure .And it has peculiar ability of inhibiting spontaneous radiation of atoms and controlling light propagation. It will be widely used in the fields of optical communication, microwave communication, integration optical and many others. One-dimensional (1D) photonic crystal can be made easily due to its simple structure and has the properties of 2D and 3D photonic crystals. These novel optical materials will probably be crucial components in the field of optical communication, so the relevant theoretical researches are valuable and wide application perspectives are expected.The summary of the dissertation is as follows:1. The historical back ground, the physical foundation and the main properties (photonic band gaps and photonic localization) of photonic crystals are introduced in chapterâ… . Different design methods and different theoretical research methods are also compared in this chapter. Finally, possible utilization and main research fields in photonic crystal are listed so that we can set the aim of the present thesis. 2. Chapterâ…¡starts from the Maxwell's equation, deduces the basic differential equation of light spreads in photonic crystal and the theory ofone dimensional optical transfer matrix. This theory has small calculationquantity and high precision in calculation and may calculate photonic band gap properties, transmission spectrum and reflection spectrum of photonic crystals.3. Chapterâ…¢describes the study actuality of one-dimension binary photonic crystal's widening of band gap , and sum up the one-dimension binary photonic crystals of the new structure which rule by the widening of band gap.(1) The ratio of the two refractive indexes, the number of cycle, and the structure of the crystal are the impact factors of one-dimension binary photonic crystal's width of band gap. The impacts are:a) The ratio of the two refractive indexes is greater, the bandwidth is wider.b) The number of cycle makes no difference to scope of band gap, just the number is bigger the edges are more obvious. After the number reaches a definite value, the band gap will steadiness. After contrast, when the other parameters being equal, the number of cycle should not be more than 20.c) The band gap of Complex-period photonic crystals is not simple formed by the band gaps of two or three ordinary photonic crystals, it has a unique band structure, in the long-wave zone appear a new band gap , this will be a wider use in practice .d) The band gap of disordered one-dimension binary photonic crystals broadens obviously. This makes a new breakthrough in the band gap widening for us. The layer-number of disorder is more, the bandwidth is wider. The number of cycle is more, the bandwidth is wider. The degree of disorder is more, the bandwidth is wider.(2) It can also achieve the effect of widening the band gap, which the new one-dimension binary photonic crystals. The advantage is. it can control the thickness of each layer accurately, and then receive a very precise band gap.a) Whether high or low refractive index medium increases, the band gap widening obviously by the arithmetic incremental photonic crystal. When the margin makes certain, the layer-number of increment is more, the bandwidth is wider. And also, the margin is more, the bandwidth is wider. When the margin of width both high and low refractive index medium are at the same ratio with the initial width of them, the movements are accordant. So we can choose the medium and their thickness, and receive inexpensive products.b) The increment-decrease of cycle photonic crystal is the cycle when it is singular, the widths are, when it is even, the widths are margin decreasing. The first band gap of this crystal almost unchanged, but two new band gaps present to its both sides. And with the increase of the margin, the new band gaps widened significantly, especially the one in the long-wave. In practice these will be good applications.c) The increment-decrease of medium photonic crystal is one medium width is arithmetic incremental, the other width is margin decreasing, andwe keep the optical thickness of a cycle 1/2 center wavelength. A new bandgap present to the short-wave by this crystal, and with the margin increasing, the new band gap and the first band gap will widen gradually.4. Chapterâ…£describes the study actuality of one-dimension ternary photonic crystal's widening of band gap, and discusses the one-dimension ternary photonic crystals of the new structure which rule by the widening of band gap. And also designs a new filter.(1) The three medium values of optical thicknesses, the relation of the three refractive indexes, the number of cycle, and the structure of the crystal are the impact factors of one-dimension binary photonic crystal's width of band gap. The impacts are:a) We usually take the optical thicknesses of the three medium are In these values,when u = -v increasing gradually, the first band gap of crystal was widening, the second band gap is narrowing, and the third band gap was widening. When u = -v=1, the crystal turned into one-dimension binary photonic crystal, and the second band gap disappeared. We can see the binary less than the ternary for the number of band gaps, so the application of one-dimension ternary photonic crystal wider.b) When the ratio of which the first and third refractive index reduced, all the band gaps will narrow. The refractive indexes of the second and the third medium are more approach, the first band gap is broader, the second band gap is narrower, and the third band gap is broader.c) The number of cycle makes no difference to scope of band gap, just the number is bigger the edges are more obvious. After the number reaches a definite value, the band gap will steadiness. After contrast, when the other parameters being equal, the number of cycle should not be more than 20.d) The band gap of disordered one-dimension ternary photonic crystals broadens obviously. The layer-number of disorder is more, the bandwidth is wider. The number of cycle is more, the bandwidth is wider. The degree of disorder is more, the bandwidth is wider.(2) We discuss the arithmetic incremental photonic crystal only for the new one-dimensional ternary photonic crystal, which base on the structure of the ternary one-dimensional photonic crystal is more complex. The following conclusions have been: when the layer number of arithmetic incremental was one, the refractive index of this medium is higher the band gap is wider, and the margin is more, the bandwidth is wider. When the layer number of arithmetic incremental was two. the band gap is the widest if the two refractive indexes are higher in these three, and the band gap is the narrowest if the two refractive indexes are lower in these three, and the margin is more, the bandwidth is wider. When the layer number of arithmetic incremental was three, the margin is more, the bandwidth is wider. When the margin was uniform, the layer number of increased is more the band gap is widener.(3) In the study of filter, we find a great distinction in band gap through compare the previous studies with our studies, which we make the opticalthicknesses of three mediums 1/4 center wavelength. The main difference isthat the center wavelength is in the forbidden band by previous studies, people can control waves which prohibited by controlling the width of the forbidden band. However, the center wavelength in the conduction band, for the new filter. We can control waves which passed by controlling the width of the conduction band. In this way, we can attain the purpose, which control some useful light-wave through the filter.