砷化鎵/氧化鋁三維光子晶體及其缺陷結構之製作與分析

Abstract

光子晶體(photonic crystal)是一種特殊的材料結構,利用不同的製程方式讓元件的介電常數(dielectric constant)產生週期性變化,形成光子晶體能隙(photonic bandgap),讓某些頻率的光無法傳播。 我們製作三維光子晶體的方法採用自我複製法(auto-cloning technique)來製作,在二維棋盤結構上,利用分子束磊晶(MBE)交替成長兩種不同比例的AlxGa1-xAs,在利用水氧化法將Al成分高者氧化形成AlxOy,增加兩者折射率的差別,形成折射率差約2的三維面心光子晶體。 在光學量測上我們探討了三種變化:改變週期數目對光子晶體能隙的影響;缺陷區域面積與缺陷模態的變化關係;非正向入射造成的光子晶體能隙變化關係等三個部分。週期增加會使得光子能隙現象更加明顯;隨著缺陷區域面積的增加我們觀察到缺陷模態產生紅位移(red shift)現象;非正向入射時光子能隙則有變寬現象。

Photonic crystal is an unique structure. It is a kind of periodic variation of dielectric constant by various fabrication processes. Photonic crystal has a special characteristic—photonic bandgap—which the light with certain frequency will not propagate in . We use the “auto-cloning technique” to fabricate three dimensional photonic crystal. On the two dimensional checker-board pattern template, we alternate periodically the depositions of two materials which have different percentage of Al composition. Our material is GaAs system. Then the refractive index difference is changed by using wet oxidation. After wet oxidation the difference is increased to about 2 to fabricate 3D-FCC-photonic crystal. The subject of our research is the influence of the following variations on the photonic bandgap: (i) periods variation; (ii) defect region size variation; (iii) oblique transmission characteristics. Increasing the number of periods will make photonic bandgap more obvious. With increasing defect size, we observed the red shift of defect modes. With oblique incidence, photonic bandgap width will increase.