Hofmann Clarissa L M, Herter Barbara, Fischer Stefan, Gutmann Johannes, Goldschmidt Jan Christoph
Opt Express. 2016 Jun 27;24(13):14895-914. doi: 10.1364/OE.24.014895.
In this paper, we present a comprehensive simulation-based analysis of the two photonic effects of a Bragg stack - a modified local density of photon states (LDOS) and an enhanced local irradiance - on the upconversion (UC) luminescence and quantum yield of the upconverter β-NaYF doped with 25% Er. The investigated Bragg stack consists of alternating layers of TiO and Poly(methylmethacrylate), the latter containing upconverter nanoparticles. Using experimentally determined input parameters, the photonic effects are first simulated separately and subsequently coupled in a rate equation model, describing the dynamics of the UC processes within β-NaYF:25% Er. With this integrated simulation model, the Bragg stack design is optimized to maximize either the UC quantum yield (UCQY) or UC luminescence. We find that in an optimized Bragg stack, due to the modified LDOS, the maximum UCQY is enhanced from 14% to 16%, compared to an unstructured layer of upconverter material. Additionally, this maximum UCQY can already be reached at an incident irradiance as low as 100 W/m. With a Bragg stack design that maximizes UC luminescence, enhancement factors of up to 480 of the UC luminescence can be reached.
在本文中，我们对布拉格堆栈的两种光子效应——光子态局部密度（LDOS）的改变和局部辐照度的增强——对掺杂25%铒的上转换（UC）发光体β-NaYF的上转换（UC）发光和量子产率的影响进行了全面的基于模拟的分析。所研究的布拉格堆栈由TiO和聚甲基丙烯酸甲酯的交替层组成，后者包含上转换纳米颗粒。利用实验确定的输入参数，首先分别模拟光子效应，随后将其耦合到一个速率方程模型中，该模型描述了β-NaYF:25% Er内UC过程的动力学。通过这个集成模拟模型，对布拉格堆栈设计进行优化，以最大化UC量子产率（UCQY）或UC发光。我们发现，在优化的布拉格堆栈中，由于LDOS的改变，与非结构化的上转换材料层相比，最大UCQY从14%提高到了16%。此外，在低至100 W/m的入射辐照度下就能达到这个最大UCQY。通过最大化UC发光的布拉格堆栈设计，UC发光的增强因子可达480。
