In the last few years, photonic crystals have gained considerable interest due to their ability to “mold the flow of light.” Photonic crystals are physically based on Bragg reflections of electromagnetic waves. In simple terms, a one-dimensional (1D) photonic crystal is a periodic stack of thin dielectric films with two different refractive indices, n1 and n2. The two important geometrical parameters determining the wavelength of the photonic bandgap are the lattice constant, a = d1(n1) + d2(n2), and the ratio of d1 to a (where d1 is the thickness of the layer with refractive index n1, and d2 is the thickness of layer n2). For a simple quarter-wavelength stack, the center wavelength λ of the 1D photonic crystal would be simply λ = 2n1d1 + 2n2d2. In the case of 2D photonic crystals, the concept is extended to either airholes in a dielectric medium or dielectric rods in air. Therefore, ordered porous dielectric materials like porous silicon or porous alumina are intrinsically 2D photonic crystals.
在过去几年中,光子晶体因其能够“塑造光的流动”而引起了相当大的兴趣。光子晶体在物理上基于电磁波的布拉格反射。简单来说,一维(1D)光子晶体是由两种不同折射率的薄介质膜周期堆叠而成,这两种折射率分别为n1和n2。确定光子带隙波长的两个重要几何参数是晶格常数a = d1(n1) + d2(n2),以及d1与a的比值(其中d1是具有折射率n1的层的厚度,d2是具有折射率n2的层的厚度)。对于简单的四分之一波长堆叠,一维光子晶体的中心波长λ简单地为λ = 2n1d1 + 2n2d2。在二维光子晶体的情况下,这个概念扩展到介质中的气孔或空气中的介电棒。因此,有序多孔介质材料如多孔硅或多孔氧化铝本质上是二维光子晶体。