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Surface Plasmons

Metal-stripe plasmonic waveguide

For in-plane confinement of surface plasmons, a metallic stripe can be used instead of a metallic film. From fabrication technology point of view, it is simplest structure for the fabrication. However, the larger optical loss is significant demerit of such in-plane confinement. Since there is a significant density of optical field near edges of the metallic stripe, the imperfection of the edges causes significant optical loss for the surface plasmons. Also, the deeper penetration of optical field inside the metallic strip is another reason for higher optical loss.


Au:SiO2 single-surface, single dielectric plasmons

Fig.1 Structure of Au:SiO2

plasmonic waveguide

Fig.2 Optical absorption of Au:SiO2 single-surface, single dielectric plasmons as function of width of metal stripe. Black line symmetric mode. Red line is asymmetric mode.

The optical loss for plasmons in Au:SiO2 film is 45 dB/mm. It is smaller than in the Au:SiO2 stripe.

Fig.3 Animated pictures. Distribution of optical field inside Au/SiO2 plasmonic waveguide for symmetric mode (left) and asymmetric mode (right), Animated parameter is waveguide width. Sizes are in um. Wavelength 1550 nm.





















Co-SiO2-AlGaAs-GaAs plasmonic waveguide (lambda=800 nm)


Fig.4 (center, animated picture) Distribution of optical field in Co-SiO2-AlGaAs-GaAs plasmonic waveguide (800 nm). Animated parameter is thickness of SiO2 layer (BetweenThickness). (right) Optical loss of surface plasmons as function of SiO2 thickness.

The optical field is significantly confined inside SiO2 layer. There is no cutoff because of thickness of AlGaAs is not sufficient


Co(strip)-SiO2-Si plasmonic waveguide (lambda=1550 nm)


Fig.5 (center, animated picture) Distribution of optical field (center) Co-SiO2-S plasmonic waveguide (1550 nm). Animated parameter is thickness of SiO2 layer (BetweenThickness). (right) Optical loss calculated for different depth of calculation window.

There is a significant confinement of optical field inside SiO2 layer

The calculated optical loss might be large than real value due to limitations of the calculation method (The dependence of calculated optical loss on the sizes of calculation window indicates the limitations of the calculation method).

It is still a challenging task for me to calculate correctly the parameters of surface plasmons in a stripe-metal waveguide near cutoff by FEM method.







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