Fig. 3: In-plane anisotropic dispersion of the waveguide modes at visible range.
From: Visible to mid-infrared giant in-plane optical anisotropy in ternary van der Waals crystals
Near-field images of Ta2NiS5 flake with a-axis on the left and c-axis on the left under (a) 633 nm (b) 785 nm excitation wavelengths, labeled in the upper right corner of each image. The white dash line represents the edge of the sample. The corresponding fringe profiles of the images are represented by the red lines. Scale bar: 1 μm. c, d Experimental dispersion data (points) and theoretical dispersion relations of TM and TE polarized waveguide modes along c-axis and a-axis, respectively. Polar plots of wavevector q along different in-plane crystallographic directions of the TM and TE modes under excitation wavelengths of (e, f) 633 nm and (g, h) 785 nm. The error bars were determined from the half of the full-width at half-maximum (FWHM) of the peak in the Fourier transform (FT) analysis69.
