Research and Development of Liquid Phase Epitaxy Grown Iron Garnet Thin Films Utilizing Plasmon Resonances for Enhancement of Magneto-Optic Effects

Abstract

Plasmon resonance induced Faraday rotation enhancement in garnet films offers the promise for development of compact and higher performance polarization dependent optical devices. Enhancement of Faraday rotation has been achieved utilizing strong localized electric fields induced by the excitation of plasmon resonances in gold nanoparticles deposited on or in garnets. Experimental results are presented that reveal strong Faraday rotation enhancement in bismuth-doped garnet films with gold nanoparticles incorporated in or on the epitaxial films. The strength of the enhancement is governed by the thickness of the garnet films, the dimensions and separations of the nanoparticle assemblies, and the relative ratio between the height of the nanoparticles and the thickness of the films.

For samples with embedded nanoparticles, there have been noticeable effects on the magnetic properties of the films due to the presence of the embedded gold nanoparticles. The embedding of nanoparticles in the films can be practically utilized to control the local anisotropy of the films. Special efforts have been made to improve the growth process and produce sub-micron thick films with thicknesses around 200nm to ensure that the induced electric fields are uniformly spread over the thickness of the films. At this thickness, nanoparticles have been incorporated on the surface of the liquid phase epitaxy grown garnet films rather than embedded in the films due to the low growth rate necessary to grow these films. New techniques have been developed to improve the accuracy of Faraday rotation enhancement measurements. Faraday rotation enhancement as high as 110% has been observed for samples with nanoparticle assemblies incorporated on the surfaces of the films but the enhancement depends on a number of factors and can be substantially lower. Stronger enhancement can be obtained by increasing the nanoparticle height to film thickness ratio as well as increasing the relative spacing between nanoparticles.