Grgić Jure, Xiao Sanshui, Mørk Jesper, Jauho Antti-Pekka, Mortensen N Asger
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
Opt Express. 2010 Jun 21;18(13):14270-9. doi: 10.1364/OE.18.014270.
Light traversing a hollow-core photonic band-gap fiber may experience multiple reflections and thereby a slow-down and enhanced optical path length. This offers a technologically interesting way of increasing the optical absorption of an otherwise weakly absorbing material which can infiltrate the fibre. However, in contrast to structures with a refractive index that varies along the propagation direction, like Bragg stacks, the translationally invariant structures studied here feature an intrinsic trade-off between light slow-down and filling fraction that limits the net absorption enhancement. We quantify the degree of absorption enhancement that can be achieved and its dependence on key material parameters. By treating the absorption and index on equal footing, we demonstrate the existence of an absorption-induced saturation of the group index that itself limits the maximum absorption enhancement that can be achieved.
穿过空心光子带隙光纤的光可能会经历多次反射，从而导致光减速并增加光程长度。这为增加原本吸收较弱但可渗透到光纤中的材料的光吸收提供了一种技术上有趣的方法。然而，与折射率沿传播方向变化的结构（如布拉格堆栈）不同，这里研究的平移不变结构在光减速和填充率之间存在内在的权衡，这限制了净吸收增强。我们量化了可以实现的吸收增强程度及其对关键材料参数的依赖性。通过平等对待吸收和折射率，我们证明了群折射率存在吸收诱导的饱和现象，这本身就限制了可以实现的最大吸收增强。
