Department of Physics and Astronomy, University of Firenze, Firenze, Italy.
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Firenze, Firenze, Italy.
Sci Rep. 2017 Mar 24;7(1):385. doi: 10.1038/s41598-017-00343-0.
Ion irradiation is a widely employed tool to fabricate diamond micro- and nano-structures for applications in integrated photonics and quantum optics. In this context, it is essential to accurately assess the effect of ion-induced damage on the variation of the refractive index of the material, both to control the side effects in the fabrication process and possibly finely tune such variations. Several partially contradictory accounts have been provided on the effect of the ion irradiation on the refractive index of single crystal diamond. These discrepancies may be attributable to the fact that in all cases the ions are implanted in the bulk of the material, thus inducing a series of concurrent effects (volume expansion, stress, doping, etc.). Here we report the systematic characterization of the refractive index variations occurring in a 38 µm thin artificial diamond sample upon irradiation with high-energy (3 MeV and 5 MeV) protons. In this configuration the ions are fully transmitted through the sample, while inducing an almost uniform damage profile with depth. Therefore, our findings conclusively identify and accurately quantify the change in the material polarizability as a function of ion beam damage as the primary cause for the modification of its refractive index.
离子辐照是一种广泛应用于制造用于集成光子学和量子光学的金刚石微纳结构的工具。在这种情况下，准确评估离子诱导损伤对材料折射率变化的影响至关重要，这既可以控制制造过程中的副作用，又可以对这种变化进行精细调节。关于离子辐照对单晶金刚石折射率的影响，已经有一些部分相互矛盾的报道。这些差异可能归因于这样一个事实，即在所有情况下，离子都被注入到材料的体中，从而诱导一系列并发效应（体积膨胀、应力、掺杂等）。在这里，我们报告了在高能（3 MeV 和 5 MeV）质子辐照下，38 µm 厚的人工金刚石样品中折射率变化的系统特征。在这种配置中，离子完全穿透样品，同时在深度上诱导出几乎均匀的损伤分布。因此，我们的发现明确地确定并准确地量化了材料极化率随离子束损伤的变化，这是其折射率变化的主要原因。
