Recognition of multipolar second-order nonlinearities in thin-film samples
Research output: Other conference contribution › Paper, poster or abstract › Scientific
|Publication status||Published - Mar 2016|
|Event||Physics days 2016 - University of Oulu, Oulu, Finland|
Duration: 29 Mar 2015 → 31 Mar 2016
|Conference||Physics days 2016|
|Period||29/03/15 → 31/03/16|
Although multipole effects have been already utilized in nanostructured materials, the design guidelines for strong multipolar responses in bulk of materials are poorly under-stood, and such responses are difficult to address reliably in experiments. Multipole ef-fects can be studied by second-harmonic generation with two non-collinear beams at the fundamental frequency [1,2]. However, this technique was originally developed for bulk samples and new materials are commonly characterized as thin films. Thus, the existing models used to interpret two-beam experiments fail in properly accounting for effects particular to thin films, including propagation effects and multiple reflections. This gives rise to significant difficulties in the recognition of multipolar nonlinearities.
We introduce a detailed model that fully accounts for all thin-film effects and show that apparent multipole nonlinearities can arise from such effects even when the nonlinearity has strictly dipolar origin. Our results show both theoretically and experimentally that reliable recognition of multipolar responses of new materials will require extremely careful experiments combined with detailed theoretical modelling.