# Suppressed Transmission of Long-Range Surface Plasmon Polariton by TE-Induced Edge Plasmon
## 3 TE-Induced Edge Plasmon
Figure 4a shows the invertedly copied plasmonic signals from the TE-polarized optical signals with the power of 15, 18 and 21 dBm and the modulated intensities are normalized to the same minimum value. The extinction ratio, and on/off ratio of the copied plasmonic signal, increases with the input optical power. We also compared the calculated decoupling length to the measured extinction ratio of plasmonic signals (Figure 4b). The blue line represents the calculated decoupling length as a function of input optical power. The vertical bars represent the measured extinction ratio for the input optical power of 15, 18 and 21 dBm. As the input optical power increases, more power is transferred to free electrons to excite the edge plasmon, and a stronger current density is induced in the G-SPPWs, thereby extending the decoupling length. Copied plasmonic signals are observed in input powers  
Figure 2: The finite-difference time-domain (FDTD) analysis of (**a**) the plasmonic mode excited by TE-polarized light in the gap (\(-2\)\(\upmu\)m\(\leq y\leq 2\)\(\upmu\)m) and (**b**) induced current densities (\(\eta_{x}\) and \(\eta_{y}\)) at the top and bottom interfaces of gapped-SPP waveguides (G-SPPWs) after normalization to the current density of the LRSPP. of over 15 dBm, and the increasing extinction ratio also follows the dependence of power on the decoupling length. This indicates that the transmission difference of LRSPPs, between the 'on' and 'off' states of the input optical signal, increases with the power given that the 'on' state of the input optical signal leads to the suppressed transmission of LRSPPs through the excitation of edge plasmon. Such a comparison illustrates that the increasing extinction ratio of copied SPP signals is linked to the TE-induced current density parallel to LRSPP propagation. We also investigated the dielectric effect on the PSC through the discontinuity of the channel waveguide. Figure 5a illustrates the top view of the PSC with a discontinuous channel waveguide and Figure 5b shows the optical microscope image of the fabricated PSC sample with a discontinuous channel waveguide. For such a structure, partial reflection and scattering occur at the end(front)-facet of the input(output) channel waveguide, and the effective index of excited edge plasmon in the gap is changed depending on the surrounding dielectric material. Figure 5c shows the copied plasmonic signals from TE-polarized optical signal with the power of 21 dBm for the continuous and discontinuous channel waveguides. It is found that the extinction ratio for the continuous channel waveguide is much larger than that of discontinuous one. The FDTD-calculated transmission of input light at the output channel waveguide does not exhibit distinct differences between the cases, which means that the reflection and scattering at the facets of the discontinuous channel waveguide is much larger than that of discontinuous channel waveguide. Figure 4: (**a**) Generated plasmonic signals by TE-polarized optical signals with the power of 15, 18 and 21 dBm in PSC. (**b**) Comparison between the calculated decoupling length and measured extinction ratio as a function of input optical power. Figure 3: The FDTD analysis of (**a**) the photonic mode excited by TM-polarized light in the gap and (**b**) induced current densities (J\({}_{x}\) and J\({}_{y}\)) at the top and bottom interfaces of G-SPPWs after normalization to the current density of the LRSPP. Note that the scale of color bar is different with Figure 2b. nel waveguide do not affect the transmission of LRSPPs across the gap, due to the small index change. However, there is a significant difference observed in the excited edge plasmon mode. The effective indices of edge plasmon modes excited by the TE-polarized light in the gap for the continuous (discontinuous) channel waveguides are 1.48737 (1.48344).