Pariente Jose Angel, Bayat Farzaneh, Blanco Alvaro, García-Martín Antonio, Pecharromán Carlos, Marqués Manuel I, López Cefe
Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Calle Sor Juana Inés de la Cruz 3, Madrid, E-28049, Spain.
Department of Physics, Azarbaijan Shahid Madani University (ASMU), Tabriz, 53751-71379, Iran.
Small. 2023 Oct;19(40):e2302355. doi: 10.1002/smll.202302355. Epub 2023 Jun 6.
By preparing colloidal crystals with random missing scatterers, crystals are created where disorder is embodied as vacancies in an otherwise perfect lattice. In this special system, there is a critical defect concentration where light propagation undergoes a transition from an all but perfect reflector (for the spectral range defined by the Bragg condition), to a metamaterial exhibiting an enhanced transmission phenomenon. It is shown that this behavior can be phenomenologically described in terms of Fano-like resonances. The results show that the Fano's parameter q experiences a sign change signaling the transition from a perfect crystal exhibiting a reflectance Bragg peak, through a state where background scattering is maximum and Bragg reflectance reaches a minimum to a point where the system reenters a low scattering state recovering ordinary Bragg diffraction. A simple dipolar model considering the correlation between scatterers and vacancies is proposed and the reported evolution of the Fano-like scattering is explained in terms of the emerging covariance between the optical paths and polarizabilities and the effect of field enhancement in photonic crystal (PhC) defects.
通过制备具有随机缺失散射体的胶体晶体，可形成一种晶体，其中无序表现为原本完美晶格中的空位。在这个特殊系统中，存在一个临界缺陷浓度，在此浓度下，光传播会经历从几乎完美的反射器（对于由布拉格条件定义的光谱范围）到呈现增强透射现象的超材料的转变。结果表明，这种行为可以用类法诺共振进行唯象描述。结果显示，法诺参数q经历符号变化，这标志着从呈现布拉格反射峰的完美晶体，经过背景散射最大且布拉格反射率达到最小值的状态，转变到系统重新进入低散射状态并恢复普通布拉格衍射的过程。提出了一个考虑散射体与空位之间相关性的简单偶极子模型，并根据光程与极化率之间出现的协方差以及光子晶体（PhC）缺陷中场增强的效应，解释了所报道的类法诺散射的演变。
