Confinement of photons, electrons and magnetism in nano/meta-materials

这个博士项目研究纳米粒子和人工纳米结构材料和表面的线性和非线性（变色）光学特性。纳米结构材料和表面（在纳米尺度上创建人工结构，例如几何形状阵列）强烈影响其光学性质。因此，设计和制造具有特定应用所需性能的纳米表面是可能的。纳米表面通常是由等离子体金属制成的。这些金属（如金、银、铝等）拥有等离子体激元（电子在这些金属表面的相干振荡），并与光发生强烈的相互作用。等离子体纳米粒子可用于研究新的光学现象，如超瑞利散射中的光学活性。在超瑞利散射中，从纳米颗粒散射的光具有入射光的两倍频率（例如，如果红光入射到纳米颗粒上，则散射光为蓝色）。光学活性意味着散射光的数量取决于入射光的圆偏振（“扭曲”）。该效应在药物分子的敏感表征中具有潜在的用途。在这个项目中，我们研究了不同几何形状的等离子体纳米颗粒悬浮液中的超瑞利散射，以更好地理解这种效应，这对未来的成功应用至关重要。该项目可能包括将化学分子附着在等离子体纳米粒子上，目的是提高它们的光学响应。作为该项目的一部分，等离子体纳米表面在提高分子光学表征的准确性、检测空气污染和其他领域具有潜在的应用。我们研究的目的是表征和优化这些结构的性能。我们还计划设计由磁性材料制成的纳米表面，目的是通过磁场调节纳米结构的光学特性。纳米粒子及其结构的研究多采用光学方法。这些包括完善的方法，如光学显微镜，以及新颖的光学实验，我们组装在我们的实验室。确切的实验配置取决于所研究的样品，但通常，我们使用超短脉冲激光作为光源，并设计我们的实验，以最大限度地提高检测样品非线性特性的灵敏度。

This PhD project studies the linear and nonlinear (colour-changing) optical properties of nanoparticles and artificially nanostructured materials and surfaces.Nanostructuring materials and surfaces (creating an artificial structure, e.g. an array of geometrical shapes, on the nanoscale) strongly affects their optical properties. Thus, it is possible to design and manufacture nanosurfaces with desired properties for specific applications. Often, the nanosurfaces are made of plasmonic metals. These metals (e.g. gold, silver, aluminium, ...) host plasmons (coherent oscillations of electrons on the surface of these metals) and interact strongly with light.Plasmonic nanoparticles can be used to study new optical phenomena, such as optical activity in hyper-Rayleigh scattering. In hyper-Rayleigh scattering, light scattered from the nanoparticles has double the frequency of the incident light (e.g. if red light is incident on the nanoparticles, the scattered light is blue). Optical activity means that the amount of scattered light depends on the circular polarisation ("twist") of the incident light. The effect has potential use in sensitive characterisation of molecules used in pharmaceuticals. In this project, we study hyper-Rayleigh scattering in suspensions of plasmonic nanoparticles with various geometries to gain better understanding of the effect, which is essential for successful future applications. The project might involve attaching chemical molecules to plasmonic nanoparticles with the aim of increasing their optical response.Plasmonic nanosurfaces studied as part of this project have potential applications in increasing the accuracy of optical characterisation of molecules, in detecting air pollution and in other areas. The aim of our research is to characterise and optimise the performance of these structures.We also plan to design nanosurfaces made of magnetic materials with the aim of tuning the optical properties of the nanostructures with magnetic field.Mostly optical methods are used to study the nanoparticles and nanostructures. These include well-established methods, such as optical microscopy, as well as novel optical experiments, which we assemble in our lab. The exact experimental configuration depends on the studied samples but, generally, we use ultrashort-pulse lasers as light sources and design our experiments in a way to maximise the sensitivity of detection of the nonlinear properties of the samples.