Figure 4. PINEM imaging of NC-based nanopatterns.

Photon-induced near-field electron microscopy (PINEM) images of the transient surface plasmon polariton (SPP) grating generated by a linear array of nanocavities (NCs; measured lengths ≃4.2, 4.3 and 4.4 μm, respectively, widths ≃260 nm), photoexcited by linearly polarized light at =0° and =20°, are shown in a and b, respectively. The area enclosed by the grey rectangle is analysed in detail in Fig. 5. Scale bars in all panels correspond to 1 μm. (c) PINEM image of the plasmonic interference pattern (PIP) generated by a linear array of short NCs (measured lengths ≃0.6, 0.7, 0.8 and 0.9 μm, respectively, widths ≃275 nm), photoexcited by linearly polarized light at =−78°. (d) PINEM image of the PIP generated by two vertically offset linear arrays of NCs (length ≃2.1 μm, width ≃270 nm), photoexcited by linearly polarized light at =−20°. The resulting SPP standing wave interference shows a periodicity of λ_SPP/2 along the vertical (counter-)propagation direction (dashed horizontal lines), yielding an estimated SPP wavelength of λ_SPP,exp=638±32 nm. The dashed elliptical shape depicts the approximate outline of the electron beam footprint. All panels are recorded at τ= 0 using λ₀=786 nm and share the linear false colour scale depicted in the middle.