Nonlinear optical properties of organo-metallic films

Abstract

Joining organic molecules and metallic nanoparticles into coupled heterostruc- tures allows tuning their optical properties and o®ers novel possibilities for manipulating their emission patterns. This Master Thesis is aimed at probing and understanding the nature of the optical coupling between plasmonic nanoparticles and organic molecules. We carry out second harmonic spectroscopy and interferometry experiments on thin flms of the nonlinear dye crystal violet deposited on glass and on top of silver nanoparticles to study the interplay between the resonance of the dye and the plasmon modes of the nanoparticles. We find a small redshift of second harmonic emission from the nanoparticles, while the molecular second harmonic resonance displays a large blueshift of tens of nanometers in the vicinity of the nanoparticles. Across both resonances a characteristic shift of ¼ in the phase of the generated second harmonic light is observed by second harmonic interferometry. To explain our ¯nd- ings, a phenomenological model with two coupled damped anharmonic oscillators is proposed. With the model, we are able to reproduce the main features of the experimental data.