Fig. 1. (a) Cross section of the DLSPP waveguide. (b) |Ey| 2D-field profile of the TM00 SPP mode for a 3.6  μm×3.6  μm DLSPP waveguide at λ=9.26  μm. (c) Top view of the 3D simulation of the waveguide.

Fig. 2. (a) Mode effective index Neff for different ridge dimensions. (b) Propagation length Lp for different ridge dimensions.

Fig. 3. (a) Influence of the PE ridge geometries on the effective mode area (Aeff/A0). (b) Comparison of the transmission (Ib/Ia) of a 90° PE DLSPP waveguide bend (cross section of 3.6  μm×3.6  μm) at λ=9.26  μm and a PMMA DLSPP waveguide (cross section of 600  nm×600  nm) at λ=1.55  μm as a function of its normalized radius (R/λ). Inset: 3D modeling of the PE waveguide mode.

Fig. 4. Schematic flow chart of the chip fabrication process, (a) using an Au hard mask and (b) using a Cr hard mask.

Fig. 5. Typical AFM image of the fabricated PE films right after spin coating. rms area roughness amounts to Sq=10.4  nm.

Fig. 6. Scanning electron microscope (SEM) image of a DLSPP PE-waveguide structure. (a) Plasmonic waveguide and (b) Closeup of the 8 µm wide and 1 µm high PE stripe.

Fig. 7. (a) Summary of measured data in terms of waveguide losses (left) and coupling losses (right) extracted from the effective cutback method. The square points represent the losses extracted with the cutback method per each waveguide width. Dashed lines represent the exponential fit of the results obtained from the simulations. (b) Mode-profile simulations of the fabricated DLSPP waveguides, indicating their respective width (w) and thickness (t) measured with a profilometer.

Fig. 8. (a) SEM images of the S-bend structures (width w=5  μm and thickness t=3  μm) with an offset of d=75  μm. (b) S-bend transmission dependence on the offset distance between the two arms (Sections A and B) obtained by numerical modeling and measurements. The inset shows the top view of the 3D simulations for offsets of d=24  μm and d=96  μm.