Advanced Wavelength Dependent Investigation of the Nonlinear Optical Properties of Organic Molecules and Carbon Nanotube Hybrids
25 January 2019
Campus Drie Eiken, N.008 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Physics
Stein van Bezouw
Wim Wenseleers & Jochen Campo
PhD defence Stein van Bezouw - Faculty of Science, Department of Physics
Organic molecules with a large second order nonlinear optical (SO NLO) response have previously found interest e.g. as active components in electro-optical modulators enabling ultra-fast modulation of light and for wavelength conversion of laser beams. In this research, a hyper-Rayleigh scattering (HRS) setup is used that is unique in the world for its wavelength tunability, accuracy, and sensitivity, to determine the SO NLO response of a wide range of organic molecules.
The HRS setup is further developed with a computer-controlled wavelength tunable optical parametric amplifier to allow automated wavelength dependent HRS measurements on a series of organic SO NLO compounds. Moreover, polarized HRS measurements, which can yield valuable information on the different tensor components of the SO NLO response of a molecule, are introduced in the setup, which includes a rigorous analysis of mixing of the polarization components of the scattering center.
The SO NLO response of several classes of molecules is measured, including compounds with a response that can be switched “on” and “off” by a change in pH of the environment, and molecules that have a larger response than what is expected based on the classical view of their ground state symmetry. Finally, molecules are encapsulated into the hollow core of carbon nanotubes (CNTs) to impose macroscopic ordering of the encapsulated molecules, in an attempt to generate nanohybrids with a huge SO NLO response. A dependence of the excitation wavelength of the encapsulated molecules on the diameter of the CNT they are encapsulated in is observed, which is explained by differences in stacking geometries of the molecules inside CNTs with different diameters, and which is an important observation for the future development of such SO NLO nanohybrids.