Department of Physics , University of Calabria , Via Ponte Bucci Cubo 33b , 87036 Rende , Italy.
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Via del Fosso del Cavaliere 100 , 00133 Rome , Italy.
ACS Appl Mater Interfaces. 2018 Jul 25;10(29):24750-24757. doi: 10.1021/acsami.8b08971. Epub 2018 Jul 13.
By structuring a luminescent dielectric interface as a relief diffraction grating with nanoscale features, it is possible to control the intensity and direction of the emitted light. The composite structure of the grating is based on a fluorescent dye (Lumogen F RED 305) dispersed in a polymeric matrix (poly(methyl methacrylate)). Measurements demonstrate a significant enhancement of the emitted light for specific directions and wavelengths when the grating interface is compared to nonstructured thin films made of the same material. In particular, the maximum enhancement of photoluminescence for a given pump wavelength is obtained at an angle of incidence that is close to the Rayleigh anomaly condition for the first-order diffracted waves. In this condition, the maximum extinction of incident light is observed. Upon excitation with coherent and monochromatic sources, photoluminescence plots show that the Rayleigh anomalies confine the angular interval of the emitted light. Being the anomalies directly related to the pitch of the diffraction grating, the system can be thus implemented as an optical device whose directional emission can be designed for specific applications. The exploitation of nanoimprinting techniques for the fabrication of the luminescent grating enables production of the device on large areas, paving the way for low-cost lighting and solar applications.
通过将发光介面结构设计为具有纳米级特征的浮雕衍射光栅，可以控制发射光的强度和方向。光栅的复合结构基于荧光染料（Lumogen F RED 305）分散在聚合物基质（聚甲基丙烯酸甲酯）中。与由相同材料制成的非结构化薄膜相比，测量结果表明，当光栅介面时，特定方向和波长的发射光得到显著增强。特别是，在接近第一阶衍射波瑞利异常条件的入射角下，获得了给定泵浦波长的光致发光的最大增强。在这种情况下，观察到入射光的最大消光。用相干和单色光源激发时，光致发光图谱表明瑞利异常限制了发射光的角度间隔。由于异常与衍射光栅的节距直接相关，因此可以将该系统实现为一种光学器件，其定向发射可以针对特定应用进行设计。利用纳米压印技术制造发光光栅，为在大面积上生产该器件铺平了道路，为低成本照明和太阳能应用开辟了道路。
