Marichy Catherine, Muller Nicolas, Froufe-Pérez Luis S, Scheffold Frank
Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700, Fribourg, Switzerland.
Laboratoire des Multimatériaux et Interfaces - UMR 5615 CNRS / UCBL, Université Claude Bernard Lyon 1, 22 avenue Gaston Berger, 69622 Villeurbanne Cedex, France.
Sci Rep. 2016 Feb 25;6:21818. doi: 10.1038/srep21818.
Photonic crystal materials are based on a periodic modulation of the dielectric constant on length scales comparable to the wavelength of light. These materials can exhibit photonic band gaps; frequency regions for which the propagation of electromagnetic radiation is forbidden due to the depletion of the density of states. In order to exhibit a full band gap, 3D PCs must present a threshold refractive index contrast that depends on the crystal structure. In the case of the so-called woodpile photonic crystals this threshold is comparably low, approximately 1.9 for the direct structure. Therefore direct or inverted woodpiles made of high refractive index materials like silicon, germanium or titanium dioxide are sought after. Here we show that, by combining multiphoton lithography and atomic layer deposition, we can achieve a direct inversion of polymer templates into TiO2 based photonic crystals. The obtained structures show remarkable optical properties in the near-infrared region with almost perfect specular reflectance, a transmission dip close to the detection limit and a Bragg length comparable to the lattice constant.
光子晶体材料基于介电常数在与光波长相当的长度尺度上的周期性调制。这些材料可以表现出光子带隙；由于态密度耗尽，电磁辐射传播被禁止的频率区域。为了表现出完全带隙，三维光子晶体必须呈现出取决于晶体结构的阈值折射率对比度。在所谓的木堆光子晶体的情况下，这个阈值相对较低，对于直接结构约为1.9。因此，由硅、锗或二氧化钛等高折射率材料制成的直接或倒置木堆备受关注。在这里我们表明，通过结合多光子光刻和原子层沉积，我们可以实现将聚合物模板直接转化为基于二氧化钛的光子晶体。所获得的结构在近红外区域表现出显著的光学特性，具有几乎完美的镜面反射率、接近检测极限的透射凹陷以及与晶格常数相当的布拉格长度。
