Gapped Surface Plasmon Polariton Waveguides for Plasmonic Signal Modulation Applications.

We investigate the characteristics of gapped surface plasmon polariton waveguides (G-SPPWs) to control a guided SPP through interaction with an applied force in the gap at a telecommunication wavelength of 1.55 μm. Gold is used as the metal in the insulator-metal-insulator waveguides (IMI-Ws). A low-loss polymer is used for the 30-μm-thick upper and lower cladding layers. The excited input SPPs propagate, jump over gaps with low coupling losses, and propagate again, even though there is a lengthy 12-μm-long gap in the G-SPPWs. The coupling loss is less than 0.05 dB for G-SPPWs with a gap up to 8-μm long, various widths up to 8 μm, and various thicknesses up to 50 nm. The normalized transmissions of the 2-μm-wide and 20-nm-thick G-SPPWs are less than -0.06 dB with various gap lengths up to 8 μm. The normalized transmissions of the 2-μm-long and 20-nm-thick G-SPPWs are less than -0.05 dB with various widths up to 8 μm. The normalized transmissions of the G-SPPWs that are 2-μm-wide and 2-μm-long are less than -0.27 dB for various thicknesses up to 50 nm. The maximum normalized transmission of -0.041 dB is obtained using the 2-μm-long, 2-μm-wide and 20-nm-thick G-SPPW. G-SPPWs have potential as a new plasmonic modulation device via control of the guided SPP through interaction with an applied force in the gap.