Theoretical description of nonlinear optical scattering processes from single particles and collections of particles

非线性光学散射方法是非线性光学光谱学与光散射方法的结合。在这样的实验中，材料的非线性光学极化率与散射物体的空间和线性光学性质一起决定了非线性散射图案。在过去的几年里，出现了各种各样的新方法，并探索了各种各样的系统。结果表明，非线性光学散射可以应用于各种研究领域，如探测金属和纳米结构、软物质系统和生物系统。与实验发展平行的还有理论工作，但这主要适用于最简单的非线性光学实验，即二次谐波散射，其光学参数受到限制。由于最近的实验表明，更复杂的实验可以在复杂的系统上进行，并且可以探测更广泛的过程和特征，因此，在理论水平上加深我们对这种测量的理解是合乎逻辑的下一步。因此，该项目的目标是对单个粒子和粒子集合（有序和无序）的非线性光学散射过程进行精确的理论建模。这意味着我们要建立一个非线性光学散射理论，在这个理论中，我们考虑了所有相关光束与粒子以及周围介质的完全线性和非线性光学响应。

Nonlinear optical scattering methods are a mixture of nonlinear optical spectroscopy withlight scattering. In such experiments, the nonlinear optical susceptibility of the material togetherwith the spatial and linear optical properties of the scattering object dictates the observedscattering pattern. In the last years a wide range of new methods has emerged anda large variety of systems have been probed. The outcome is that nonlinear optical scatteringis ready to be used in a variety of research fields, like probing metal and semiconductornano-structures, soft matter systems, and biological systems.In parallel to the experimental developments there has been theoretical work as well, butthis mainly applies to the simplest nonlinear optical experiment possible, second harmonicscattering, with a restricted set of optical parameters. Since recent experiments have shownthat more complicated experiments can be performed on complex systems and that a muchwider range of processes and features can be probed, it is a logical next step to deepen ourunderstanding of such measurements on a theoretical level.The aim of the project is therefore to perform exact theoretical modelling of nonlinearoptical scattering processes on single particles and collections of particles, ordered anddisordered. This means we want to formulate a nonlinear optical scattering theory, wherewe take into account the complete linear and nonlinear optical response of all the involvedbeams with both the particle as well as the surrounding medium.