Design and analysis of a surface plasmon polariton modulator using the electro-optic effect

A metal-insulator-metal (MIM) waveguide with a periodic change of dielectric materials in its insulator layer is proposed to create a voltage-controlled one-dimensional plasmonic Bragg reflector. KNbO(3) is used as one portion of the dielectric material so that the refractive index of the insulator layer can be varied by an external applied voltage. In our analysis, the transfer matrix method is employed to design and optimize the transmission spectra of the MIM waveguide Bragg reflector. The reflectivity at the on (bias voltage of 65 V) and off (bias voltage of -65 V) states is shown to be >74% and <7%, respectively, for the operating wavelength of 1.5 mum. The results are also verified by the finite-difference time-domain method. Furthermore, the modulation response of the MIM waveguide is studied. For the device area and average insulator layer thickness to be 10 mumx40 mum and 615 nm, respectively, it is found that the turn-on reflectivity of the waveguide is only slightly reduced to 69% at the -3 dB point in comparison with 75% for its steady-state performance.