Deparis Olivier, Vandenbem Cédric, Vigneron Jean Pol
Laboratoire de Physique du Solide, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.
Opt Lett. 2007 Mar 15;32(6):686-8. doi: 10.1364/ol.32.000686.
Light can tunnel through a high-reflectivity dielectric multilayer film when a photonic-crystal-type defect is introduced in the structure, which is useful for optical signal processing. We consider chirped structures with a defect in layer thickness for which high reflectivity is achieved over a broad wavelength range except within a narrow spectral window. The useful transmission window, while it shifts toward shorter wavelengths as the angle of incidence of the light beam is increased, does not, in general, survive; i.e., transmission disappears progressively. We show that wide angular range operation can, however, be achieved by a proper design of the chirped structure. Analytical expressions for the design parameters are derived on the basis of a semi-infinite photonic crystal model. Theoretical reflectance spectra of defect SiO2/TiO2 chirped multilayer films are presented and discussed in terms of the dispersion of the electromagnetic radiation modes of the finite photonic crystal. These devices offer a simple way to mechanically tune (through inclination of the film) the wavelength transmitted from a fixed white-light beam.
当在结构中引入光子晶体型缺陷时，光能够隧穿过高反射率的介质多层膜，这对于光信号处理很有用。我们考虑层厚存在缺陷的啁啾结构，对于这种结构，除了在一个窄光谱窗口内，在很宽的波长范围内都能实现高反射率。有用的透射窗口虽然会随着光束入射角的增加而向较短波长移动，但一般不会一直存在；也就是说，透射会逐渐消失。然而，我们表明通过对啁啾结构进行适当设计可以实现宽角度范围的操作。基于半无限光子晶体模型推导出了设计参数的解析表达式。给出了缺陷型SiO₂/TiO₂啁啾多层膜的理论反射光谱，并根据有限光子晶体的电磁辐射模式色散进行了讨论。这些器件提供了一种简单的方法来通过薄膜倾斜（机械方式）调节从固定白光束透射的波长。
