基于环形微腔的多频段三角晶格光子晶体耦合腔波导光学传输特性

本文理论研究了近红外波段硅基三角晶格光子晶体环形微腔的光场局域特性，通过将微腔在空间周期性排列组成耦合腔光波导，研究了多个导带区域内光束传输时的群速度，最大和最小值分别为0.0028c和0.00028c.将环形微腔在垂直于光传输方向上进行交错排列，通过改变相邻微腔之间的耦合区域，可以大幅降低多频段范围内光束在耦合腔波导中传输时群速度之间的差异，并提高部分频段的透过率数值.在不改变介质柱半径条件下，通过去掉三角晶格光子晶体中距中心介质柱距离分别为2a和√3a的六个介质柱构成了两种微腔，研究了两种微腔所支持的谐振波长之间的差异，在此基础上构造了两种耦合腔波导，进而将这两种耦合腔光波导与W1型输入/输出波导相连，最终实现了在多个不同频率范围内降低群速度的同时实现频段选择和频段分束功能，其导模群速度可降低到0.00047c.

Optical transmission characteristics of multi-band triangular-lattice photonic crystal coupling cavity waveguide based on annular microcavity

The light localization characteristics of the near-infrared triangular-lattice photonic crystal annular microcavity are studied theoretically in this paper. The photonic crystal has a lattice constant of a=540 and it is composed of silicon rods each with a radius of r=135 immersed in air background. The two kinds of annular microcavities are obtained by removing 12 silicon rods which are located respectively at a distance of 2a and at a distance of √3a to the central rod. Five resonant wavelengths and the corresponding eigen mode profiles of the microcavity are studied. A coupled resonant optical waveguide is formed by integrating the microcavities with a periodic length of 7a in space. The group velocity of light beam propagation within multiple guiding bands are analyzed by the tight-binding approximation method. The maximum and minimum velocity of 0.0028c and 0.00082c are obtained, where c is the light velocity in vacuum. The light transmittance values and spatial steady distributions of the electric field's amplitude through the structure at several wavelengths within the guiding bands are studied by the finite-difference time-domain method. The results are consistent with that calculated by the plane wave expand method. Interleaving circular microcavities perpendicular to the direction of optical transmission at a lateral distance of 2√3a, the coupling region between the adjacent microcavities is changed, the difference in group velocity between guiding bands apparently decreases and the transmittance values of two frequency bands are enhanced. Keeping the size of silicon rods unchanged, two kinds of microcavities are constructed by removing the six rods with the distances of 2a and √3a from the center of the central silicon rod, respectively. The resonant wavelengths supported by the above two microcavities are studied. Two coupled-resonant optical waveguides with a periodic length of 7a are proposed. Connecting these two coupled cavity optical waveguides with the W1-typed input/output waveguides, the selecting and sharing function of guiding band are finally achieved for wavelengths within different frequency bands. Keeping the group velocity slowing down, a maximum value of one guiding band reaches 0.00047c.