Figure 4

Dual DLSPPW coupler studied by NFES with different wavelengths. (a) SEM image of DLSPPW-based dual waveguides coupler. (b) Leakage radiation images of SPP waves propagation in the coupler from λ = 700 to 800 nm wavelengths. Cyan dash line showed the coupling length was decreased with the incident wavelength. (c) The measured and calculated coupling lengths as a function of wavelength. Red line shows the calculation results. Black line shows the measured results.