This thesis focuses on nonlinear optical (NLO) properties of two-dimensional (2D)layered materials and presents the results divided in three parts. The second- and third-order nonlinear susceptibilities of four different transition metal dichalcogenides (TMDs) are examined in the first part. The second part focuses on NLO properties of black phosphorous (BP). The third part examines the utilization of atomic layer deposition (ALD) for creating novel waveguide structures on silicon on insulator (SOI)platform. Also, the potential for integrating 2D materials on SOI waveguides for enhancing the performance of NLO devices, is presented in the last part. Monolayers of four different TMDs (i.e. MoS2, MoSe2, WS2 and WSe2) were investigated by measuring second- and third-harmonic generation (SHG, THG) simultaneously from all four materials. All four TMDs were found to possess large third-order nonlinear susceptibilities, 2-4 times larger than that of graphene, which is know to have very large third-order nonlinear susceptibility. Furthermore, it was found that the contrast in the THG between the grains and grain boundaries in chemical vapour deposition (CVD) grown MoS2 is enhanced due to the chemicals commonly used in the transfer process of 2D materials. This effect provides an opportunity for utilizing THG microscopy for rapid characterization crystal domains in CVD grown TMDs.THG microscopy was used to investigate the anisotropic properties of BP. It was shown that the THG is highly anisotropic and can be used for rapid characterization of the crystallographic orientations of very large-area BP samples. Novel waveguide structures were fabricated by coating SOI slot waveguides with organic/inorganic ALD nanolaminates. This offers potential for integrating 2D materials with SOI waveguides, as the mode can be concentrated into locations where the interaction with the 2D material and the propagating mode is maximized.
|Translated title of the contribution||Kaksiulotteisten materiaalien epälineaariset optiset ominaisuudet|
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- two-dimensional materials
- nonlinear optics
- multiphoton microscopy
- silicon photonics