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

非线性光散射方法是非线性光谱学和光散射的结合。在这样的实验中，材料的非线性光磁化率与散射物体的空间和线性光学性质一起决定了观察到的散射模式。在过去的几年中，出现了各种各样的新方法，并对各种各样的系统进行了探索。其结果是，非线性光学散射已经准备好用于各种研究领域，如探测金属和半导体纳米结构，软物质系统和生物系统。与实验发展平行的还有理论工作，但这主要适用于可能的最简单的非线性光学实验，二次谐波散射，具有一组有限的光学参数。由于最近的实验表明，可以在复杂的系统上进行更复杂的实验，并且可以探索更广泛的过程和特征，因此在理论层面上加深我们对此类测量的理解是合乎逻辑的下一步。因此，该项目的目的是对单粒子和粒子集合（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，我们考虑到所有涉及的光束对粒子和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.