光子晶體平板共振腔之特性分析

Abstract

本論文中，我們模擬分析了各種光子晶體平板微共振腔的品質因子。由於光子晶體具有布拉格反射和全反射的效應，光可以侷限在缺陷中，這類光子晶體可用於製作光子晶體雷射和提昇發光二極體的外部量子效率。我們利用有限時域差分法，針對六角晶格缺陷結構的光侷限特性進行模擬。先探討結構週期數和厚度對品質因子的影響，接著修正缺陷空腔附近空氣柱大小和位置，分析其與激發模態的關係，及相應品質因子的大小，此外分別討論垂直方向和平面方向的光侷限機制與影響品質因子的程度。在某些結構下，只需稍微適當的改變缺陷附近的結構，便可有效增進品質因子，而不用大幅地改變整體結構使得模態體積也增加。最後我們提供一些結論，以供設計製作光子晶體雷射和高效能發光二極體參考。

In this thesis, the quality factor of various kinds of photonic crystal slab microcavites is numerically investigated. Light is confined within the defect region by the combined action of distributed Bragg reflection and total internal reflection. This kind of photonic crystal has been employed in making photonic crystal lasers and a semiconductor light-emitting diode (LED). By using the finite-difference time-domain (FDTD) method, we simulate the characteristics of light confinement for the hexagonal-lattice microcavity consisting of a single defect to calculate the quality factor. The relations between quality factor and the periods of air holes around the defect and the thickness of slab are demonstrated. Then, the positions and shapes of nearest holes are adjusted to excite more defect modes, and the relation between defect modes and modified cavity in defect region are discussed. Moreover, the mechanism of light confinement in vertical and plane direction is discussed, and how they effect the quality factor can be induced. In some structures, we only need to perform small adjustment of the defect geometry to get better quality factor, without significantly changing the photonic crystal structure and increasing the mode volume. Finally, we provide some conclusions, which will be helpful for designing photonic crystal laser and efficient LEDs.