研究了金属-介质-金属(MDM)型表面等离子体激元(SPP)光波导的电磁特性。 理论计算结果表明,对于633 nm的TM偏振入射光,当介质膜层厚度小于85 nm时,波导中只能激 发产生一阶SPP模(基模),其余高阶模全部截止。随着介质膜厚度增加,高阶SPP模逐渐被激发产生。 当介质膜层厚度较小时, SPP模有效折射率的实部随阶数增加而减小,而虚部则随阶数增加 而增加, SPP基模具有最大传输距离。然而,当MDM波导中的介质层厚度超过0.555 μm时, 由于三阶SPP模的电磁场主要集中在离金属层相对较远的介质层中,其有效折射率的虚部具 有最小值,具有最大的传输距离,而非基模。当入射光波长为633 nm,介质层厚度 为0.9 μm时, Ag/SiO2 /Ag光波导中三阶SPP模的传输距离达到约150 μm。

The characteristics of EM in dielectric-metal-dielectric (MDM) surface plasmon polaritons (SPPs) waveguides were presented. The numerical results show that the waveguide can only excitate the first order SPP mode (fundamental mode) for the wavelength of 633 nm, if the dielectric film thickness is less than 85 nm. With the dielectric film thickness increasing, progressively high order SPP modes are excited. The real part of the effective refractive index decreases with increasing the order of the SPP modes, but that of the imaginary part shows an opposite trend. However, when the dielectric layer of the MDM waveguide thickness is more than 0.555 μm, since the third-order mode of the electromagnetic field SPP concentrated in relatively distant from the metal layer, the effective refractive index has a minimum value of the imaginary part. So the third-order SPP mode has a maximum propagation distance. When the wavelength of the incident light is 633 nm, the dielectric layer thickness is 0.9 μm Ag/SiO2 /Ag, the transmission distance of the third-order SPP mode is about 150 μm in the waveguide.