# Localized Surface Plasmon Fields Manipulation on Nanostructures Using Wavelength Shifting
## 3 Results  
Through the calculations, we quantitatively identified the distributions of localized plasmonic near-field generated on I-, T- and Y-type nanostructure arrays resulting from different wavelength of incident light source. Figure 2 illustrates the calculated distributions of plasmonic near-field when the upward-direction TM mode of four wavelengths light was illuminated to the I-shaped nanostructure arrays. The simulation result indicates that the position of the highly localized electromagnetic field on the structures moves further from the initial incident-light position when the wavelength becomes longer. The enhanced intensity of the localized electromagnetic fields was the largest at a wavelength of 1550 nm. In contrast, the field was localized in the same direction in which the light at 808 nm entered for the profile measurement to the center of the nanorod. When the light was 1064 nm, localized and enhanced electromagnetic fields in both directions occurred in the profile to the center of the nanorod. For sufficiently large wavelengths (1310 and  
Figure 1: (**a**) Schematics and specifications of I-, T-, and Y-shaped gold nanostructures applied in numerical simulations of plasmonic fields. The period of each nanostructure was 3-\(\upmu\)m long and 8-\(\upmu\)m wide. (**b**) SEM images of I-, T-, and Y-shaped nanostructures fabricated by electron-beam lithography to validate that each nanostructure can be established. (**c**) Schematic of simulation conditions under which light enters the nanostructures. The thickness of each nanostructure was 100 nm. 1550 nm), plasmonic fields were localized in the middle of the opposite direction to the incident light as illustrated in the intensity analysis of Figure 2f. It was apparent that the electromagnetic field distributions on the T-shaped nanostructure arrays are significantly different from the simulation result of the I-shaped nanostructure arrays as depicted in Figure 3. With the 808-nm light introducing, the localized electromagnetic fields were placed on the nanowire as the T-shaped nanostructures operated on a nanoscale grating. For sufficiently large wavelengths (1330 and 1550 nm), the near-field distribution was moderately similar to the simulation result of the I-shaped nanostructure arrays at center of nanorod. In contrast, the profile analysis at the line (2) which cross the center of nanorod for the 1550 nm incident light indicates that the electromagnetic field was highly localized at the center of T-shaped structure as illustrated in Figure 3a,f. Figure 2: Simulation results of plasmonic near-field electromagnetic fields distributions for I-shaped nanostructure arrays by incident light with wavelengths of (**a**) 1550, (**b**) 1310, (**c**) 1064, and (**d**) 808 nm. Intensities of localized electromagnetic fields at (**e**) the edge (profiled line (1)) and (**f**) the center (profile line (2)). The information of incident light source is indicated in (**b**). Figure 4 describes the distribution of plasmonic electromagnetic fields on Y-shaped nanostructure arrays when the light at the four selected wavelengths entered. The overall propensity is similar to the T-shaped nanostructure arrays-based simulation result; however, the simulation results for the case of introducing 808 nm-wavelength lights to the Y-shaped array indicates that localized plasmonic fields were placed on the tilted nanorod as described in Figure 4d. Also, there was loss of the localized field at the center of the Y-shaped structure which was observed at the T-shaped structure. The most interesting point is that not only the scanning mode of the confined field along the nanostructure but also the discrete switching mode of the confined field was observed on the Y-shaped nanostructure arrays, and it can be controlled by the wavelength. Depending on the demands for s specific confined field mode, the mode can be tuned by selecting the proper wavelength of incident light.