Figure 5. Imaging of polariton waveguide modes near the hBN edges.

(a) Experimental schematic is similar to Fig. 3a except that imaging here is performed near the edge of an unpatterned sample. (b) Near-field amplitude image measured at 1,420 cm⁻¹. The olive square indicates the area whose expanded view is shown in c–e). (c–e) Near-field image of the area marked in b at several frequencies. hBN thickness in b−e: 31 nm. (f) Near-field image of 105-nm-thick hBN at 1,400 cm⁻¹. The cyan dashed lines in b−f indicate the hBN edges. Scale bar in b−f, 300 nm. (g) Line traces perpendicular to the hBN edge. Trace α was extracted from the image in f. Traces β, γ and ζ were obtained from the Fourier analysis of the trace α as described in the text. (h) The Fourier transform of trace α in g.