Nanostructure of Technology for Making Photonic Crystals

过去光学微腔器件，如垂直腔面发射激光器（VCSELs）[1]的迅速出现，很大程度上归因于半导体晶体生长过程中高精度的层厚控制。高反射率反射镜可以以亚纳米精度生长，以定义垂直尺寸上的高Q空腔。最近，通过创建二维和三维周期结构来微制造高反射率镜子也成为可能。这些周期性的“光子晶体”可以被设计成打开电磁波传播被禁止的频带，而不考虑在空间中的传播方向，并定义光子带隙[2,3]。当与高折射率对比板相结合时，光可以有效地引导，微分叉的二维光子隙镜为我们提供了将光限制在极小体积内所需的几何形状[4,5]。在光子带隙结构中引入缺陷，形成了带有微加工反射镜的二维法布里-珀罗谐振腔。然后可以通过改变缺陷周围微结构的精确几何形状来光刻调整这些空腔。令人惊讶的是，我们发现二维光子带隙晶体中由单个缺陷组成的小腔仍然可以表现出高Q值，并且我们通过时域有限差分（FDTD）建模计算出Qs在25,000[6]范围内。在吸波半导体材料中测量实际空腔时，测得的Q值超过1500。我们已经证明，作为我们之前NSF合同的一部分，这些高q使得现在可以定义在室温下工作的微腔激光器[7]，模式体积小至2.5 (l/2nslab)3，或0.03 um3在InGaAsP中以1.55 um发射。

The past rapid emergence of optical microcavity devices, such as Vertical Cavity Surface Emitting Lasers (VCSELs) [1] can be largely attributed to the high precision over the layer thickness control available during semiconductor crystal growth. High reflectivity mirrors can be grown with sub-nanometer accuracy to define high=Q cavities in the vertical dimension. Recently, it has also become possible to microfabricate high reflecti-vity mirrors by creating two- and three-dimensional periodic structures. These periodic "photonic crystals" can be designed to open up frequency bands within which the propagation of electromagnetic waves is forbidden irrespective of the propagation direction in space and define photonic bandgaps [2,3]. When combined with high index contrast slabs in which light can be efficiently guided, microfaricated two-dimensional photonic badgap mirrors provide us wit the geometries needed to confine light into extremely small volumes [4,5]. 2-D Fabry-Perot resonators wit hmicrofabricated mirrors are formed when defects are introduced into the photonic bandgap structure. It is then possible to tune these cavities lithographically by changing the precise geometry of the microstructures surrounding the defects. Surprisingly, we have found that small cavities consisting of single defects in a two-dimensional photonic bandgap crystal can still exhibit high Q values, and we have calculated, by finite-difference time-domain (FDTD) modeling, Qs in the range of 25,000 [6]. When real cavities are measured in absorbing semiconductor material, Q values ain excell of 1500 are measured. We have shown, as part of our previous NSF contract, that these high Qs make it now possible to define microcavity lasers [7] which functio at room temperature [8], with mode volumes as small as 2.5 (l/2nslab)3, or 0.03 um3 in InGaAsP emitting at 1.55 um.