Photonic Crystals In The Slow Light Device, The Application Of Basic Research

Slow light technologies have varieties of practical application. The traditional slow light technologies are achieved mainly via material dispersions, the related experimental conditions are so strict that they are hard to meet. In contrast to which, the slow light technology achieved by photonic crystal waveguide has many incomparable advantages. In this thesis, we develop an investigation on the slow light phenomena in photonic crystal waveguides, and presents three approaches for slow light technology based on photonic crystal waveguide, which lies in the following three aspects:1. We design a new type of two-dimensional photonic crystal dispersion-free waveguide of slow light, and investigate the transmission performance of TE modes in such a waveguide. The slow light waveguide is constituted by introducing the defects of square air holes in the photonic crystal with complete lattice, where the slow light effects are formed by means of backscatter of light pulses from quadrate air holes. In order to get a ideal dispersion curve, we study the impacts of square air holes on the slow light properties of the waveguide, based on which we optimize the structure of the device and achieve a ideal slow-light effect, that is, in the center wavelength of1550nm we obtain a slow light with the slow-light factor of65and the bandwidth of8nm. Further, we analyze the dispersion curves of this structure, and obtain the group velocity dispersion(GVD) being less than104. With the aid of finite difference time domain(FDTD) we show that a remarkable time delay occurs after the light pulse passed through the slow light waveguide, where the pulse-width spreading is below5.2%.2. We investigate the slow light properties of photonic crystal coupled waveguide and design a new type of slow light coupled waveguide. The coupled waveguide is formed by introducing two line defects into the triangular lattice, which can simplify the production process. In compare with the traditional coupled waveguide, this structure could realize a flat S-shaped dispersion curve only via the optimization of two structural parameters. The distribution of the waveguide’s group refractive index vs frequency is Gaussian with an extreme value of3823. By chirping the width of the waveguide the dispersion compensation could be achieved well, we finally achieve a ideal slow-light effect in the center wavelength of1550nm with the slow-light factor of28and the bandwidth of13.24nm, the FDTD algorithm show that the waveguide has a smaller transmission loss, the coupling efficiency is as high as90%, which is a great of significance in optical communication systems.3. In order to reduce the difficulty of production process and simplify the structure of the slow light waveguide, we investigate the slow light properties of one-dimensional photonic crystal grating and design a new slow-waveguide grating structure. By further optimizing the structure parameters we have achieved a ideal flat S-shaped band structure with two inflection points, in flat region of the band structure the group refractive index is as high as7023. Using the scale invariance of the Maxwell equations, we alter the structural parameters of the device in the same proportion so as to achieve dispersion compensation well. Ultimately, we get a ideal slow-light effect in the center wavelength of1550nm with a slow-light factor of26.5and a bandwidth of15.5nm, the FDTD algorithm show that the light pulse passes through the slow light waveguide with pulse-width spreading is only2.67%, which show this structure could achieve a desired effect of slow light.