Abstract
Surface plasmonic polariton (SPP) for the use of bio-sensing has been widely studied. In this thesis, SPP combined with magneto-optical effect is used for enhancing the sensitivity of the device. We designed a sub-wavelength grating structure made from Au/Fe/Au composite layers simultaneously achieving the advantage of low optical absorption of gold and high permeability characteristics of iron. The grating structure used in this experiment not only can be able to remove the prism which the conventional surface plasmon sensor requires but also satisfy the conditions of surface plasmon coupling in normal incident situation. Unlike the general prism setup that the SPP is coupled from the back side of structure, the grating coupler can be able to excite the SPP wave on the top of the grating and reduced the absorption of surface plasmon from ferromagnetic material. Based on these characteristics, the structure designed in this thesis can increase the thickness of ferromagnetic material to improve the magnetization without inducing more absorption and enhanced the magneto-optical signal significantly. The experimental results agree well with the analysis of magneto-optical signal enhanced by SPP near the surface plasmon resonance wavelength. The estimated sensitivity of our structure is 1.7 times larger than the grating coupler without including the magneto-optical effect. And the sensitivity of Au/Fe/Au SPP grating coupler designed in our experiment is 4 times larger than the Au/Fe/Au SPP sensor through prism couplers.