Kim Kwang-Hyon
Institute of Physics, State Academy of Sciences, Unjong District, Pyongyang, Democratic People's Republic of Korea.
Phys Chem Chem Phys. 2020 Apr 8;22(14):7300-7305. doi: 10.1039/d0cp00150c.
Despite the great importance of high-index materials for dielectric nanophotonics, their optical functionalities are significantly limited for diverse photonic applications and thus, the usability of low-index materials should be explored. This work proposes the use of metallic substrates for low-index dielectric metasurfaces for significantly enhancing the local field and their optical responses. Plasmon-assisted dipole resonances mainly contribute to field enhancement in dielectric nanoparticles comprising the metasurfaces, where the intensity enhancement increases on decreasing the index of the nanoparticles when supported by metallic substrates. Another challenge with the current high-index materials is strong optical losses in the blue-ultraviolet range, which limit their practical applications such as harmonic generations in this spectral range. For a pump with a peak intensity of about 3.4 GW cm-2, a metasurface of lithium niobate nanodisk array supported by a gold substrate generates second harmonic at 400 nm with an efficiency of about 5 × 10-2%, which is one order of magnitude higher than the previously reported efficiency of harmonic generation in this range. The results presented in this work promise the significant extension of the current nonlinear nanophotonics, which is limited to high-index semiconducting materials.
尽管高折射率材料对于介电纳米光子学非常重要，但其光学功能在各种光子应用中受到显著限制，因此，应探索低折射率材料的可用性。这项工作提出使用金属衬底来制备低折射率介电超表面，以显著增强局部场及其光学响应。等离子体辅助偶极子共振主要有助于增强构成超表面的介电纳米颗粒中的场，当由金属衬底支撑时，纳米颗粒的折射率降低，强度增强增加。当前高折射率材料的另一个挑战是在蓝紫外范围内存在强烈的光学损耗，这限制了它们在该光谱范围内的实际应用，如谐波产生。对于峰值强度约为3.4 GW/cm² 的泵浦光，由金衬底支撑的铌酸锂纳米盘阵列超表面在400 nm处产生二次谐波，效率约为5×10⁻²%，比此前报道的该范围内谐波产生效率高一个数量级。这项工作展示的结果有望显著扩展当前限于高折射率半导体材料的非线性纳米光子学。
