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Study Of Device Design And Its Light Guiding Properties Of Generalized Photonic Crystal

Posted on:2015-02-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:L H WangFull Text:PDF
GTID:1268330431455078Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Photonic crystals from the date of proposed is in focus for its periodic dielectric structure, which gives the electromagnetic wave propagating in photonic crystals a band structure mode, and can lead to the generation of photonic band gap. When the frequency of electromagnetic waves happens to fall in forbidden band, the electromagnetic waves will not be able to penetrate this kind of medium. This feature makes photonic crystals become a new means to effectively control the behavior of electromagnetic waves. With the development of the research, it was found that the conduction band of photonic crystals have many use as well. As some certain areas of the conduction band of photonic crystal has special dispersion relations, the propagation of electromagnetic waves in certain frequency range will show unusual behavior, Such as the super prism effect, negative refraction effect, since the collimation effect, etc. These effects have huge potential application value in optical integration, high-density optical storage and high sensitive biological sensors and other fields. In recent years, the research on dispersion characteristics and potential applications of photonic crystal has been highly valued by the international scientific circle. Science magazine choose negative refraction research as one of the top ten scientific and technological achievements in2003. The development and application of the research will have an incalculable impact on the future of photovoltaic technology.Although there are a lot of research on photonic crystals and their optical properties, most is for standard type photonic crystal as the gradient photonic crystals with its long-range disorder short-range order provides more research content. In this paper, several new gradient photonic crystals are proposed, the characteristics of the photonic crystal is studied, using the known and the new proposed gradient photonic crystals, photonic crystal device is designed, and the simulation is done by using the plane wave expansion method and finite difference time domain method. Then we prepare regular square photonic crystal which improves LED luminous efficiency by using double-beam exposure method.The focus of this article is mainly manifested in the following two aspects:1、Research on the gradient photonic crystalsResearch on properties of conventional photonic crystal is comparatively mature, while there is still a lot of space in research on gradient photonic crystal as well as the device design. From the third chapter to the fifth chapter, we proposed several new gradient photonic crystals and their optical properties are studied, also we design several photonic crystal devices.In the third chapter, we design a new kind of photonic crystal splitter by using radiant gradient photonic crystal. The beam splitter is consist of two identical symmetrical about the horizontal axis of radiant photonic crystal1/4circular arc. To increase the beam splitter transmittance, we add the tetragonal self-collimation photonic crystal structure. By magnifying the defect of self-collimation photonic crystal, the total transmittance of photonic crystal splitter got a lot of ascension. And we can easily adjust the ratio of beam splitter. Radiant gradient photonic crystal splitter has great potential for application in optical integration. The fourth chapter puts forward a new type of circular gradient photonic crystal, a kind of deformation structure of the conventional two-dimensional photonic crystals, of which the conduction band property is mainly considered here. Using this new type of circular gradient photonic crystal, we implemented asymmetry transmission of light and frequency selective optical coupler. Due to the directional band gap of circular gradient photonic crystal, light from one direction can transmit through the photonic crystals, but can’t do it from the other direction. Using this structure, we realize the asymmetry transmission of light on numerical simulation, and a higher contrast ratio is obtained. Thanks to the light focusing phenomenon in specific frequency range of the circular gradient photonic crystal, the light through this photonic crystal is gathered in the photonic crystal waveguide, and very high coupling efficiency is gotten. When the parameters of the circular gradient photonic crystal are changed, the corresponding frequency of the peak transmissivity will change to get the optical coupler with frequency selective effect.The fifth chapter puts forward a new gradient photonic crystal structure, which does not contain nonlinear and anisotropic materials. It is obtained by changing the rods’radii along both horizontal and vertical directions. Due to the directional band gap and self-collimation effect of the square gradient photonic crystal, light from one direction can transmit through the photonic crystals, but can’t do it from the other direction. Using this structure, we realize the asymmetry transmission of light on numerical simulation, and a higher contrast ratio is obtained.2. Holographic fabrication of photonic crystals by double-beam exposure method for improving the extraction efficiency of LEDLED, for its characteristics of low power consumption, long life, small volume, become a new type of green energy-saving lighting devices. But the low Light extraction efficiency shortens the service life of LED, and causes a large number of energy losses. As an effective way to enhance the efficiency of the LED, photonic crystal became one of the hottest researches at present. With the characteristics of rapid preparation, one-step molding and low cost, holographic interference technique makes it possible to achieve higher rate of photonic crystal LED at a low cost.In the sixth chapter, we use the double-beam double exposure method to create PhCs, the optical path is simple and easy to adjust, and PhCs are one-step forming. In the experiment,532nm laser is used as the light source, which is more accessible and has more advantages in platform building and light path adjustment. The photopolymer SU8polymerized at532nm and created2D PhCs with duty cycle1:1. The PhCs structures are transferred to ITO layer of GaN blue LED and the light extraction efficiency was increased by20%-27%. The research of improving the efficiency of light extraction by PhCs still needs further improvement and perfection, but this design of PhCs creation system is simple, low cost and suitable for industrial production, so it has bright prospects.To sum up, this paper not only proposed a variety of gradient photonic crystal structure and studied the optical properties of gradient photonic crystals, but also designed a variety of optical devices using the gradient photonic crystals. At the end of the paper, we proposed the double beam twice exposure method to prepare photonic crystals and improve LED luminous efficiency by the photonic crystals prepared. The results obtained in this paper have important reference value for optical integration and energy utilization.
Keywords/Search Tags:Photonic crystal, Gradient photonic crystal, Photonic crystal splitter, Asymmetrical transmission, Double-beam exposure method, Extraction efficiency of LED, Optical coupler
PDF Full Text Request
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