Observation of Dyakonov Surface Waves

We report the first experimental observation of Dyakonov surface waves existing at the interface of transparent anisotropic crystals. A Otto-Kretchmann configuration was used to excite the surface waves at the interface between a potassium titanyl phosphate biaxial crystal and an index-matching liquid fulfilling the conditions at which the waves exist. The signature of surface wave excitation was obtained by using enhanced polarization-conversion reflectance phenomena. We measured the cutoff propagation angles for different index-matching liquids, confirming the high sensitivity of the propagation conditions with the properties of the supporting interface.

Figure 1

Experimental setup.

Figure 2

Reflectance spectra for (a) ${\mathrm{TE}}_{\mathrm{in}}\mathrm{\text{−}}{\mathrm{TE}}_{\mathrm{out}}$, (b) ${\mathrm{TM}}_{\mathrm{in}}\mathrm{\text{−}}{\mathrm{TM}}_{\mathrm{out}}$, (c) ${\mathrm{TE}}_{\mathrm{in}}\mathrm{\text{−}}{\mathrm{TM}}_{\mathrm{out}}$, input-output polarization. (d) Magnification of the small (red online) rectangle in (c). The lines labeled with ${\phi }_{\mathrm{cl}}$, ${\phi }_{\mathrm{cy}}$, and ${\phi }_{\mathrm{ce}}$ are the critical angles between the prism and the index-matching liquid, the refractive index $n_y$, and the extraordinary refractive index of the KTP crystal, respectively. The large rectangle (blue online) shows the area corresponding to the experimental image in Fig. 3a.

Figure 3

Experimental observation for an M1.795 liquid (a) image obtained by CCD camera for $\theta =30.4°$. Dimensions of the image in degrees: $0.21°\times 0.16°$ The rectangle indicates the portion of the image shown in (b) at $\theta =30.4°$, (d) at $\theta =30.5°$, and (f) at $\theta =30.7°$. (c), (e), and (g) show the integrated intensity along the lateral direction for images (b), (d), and (f), respectively.

Figure 4

Experimental cutoff angle ${\theta }_{\max }$. The results are presented for five different index-matching liquids (squares) together with the theoretical cutoff angle at $T=23.0°\mathrm{C}$ (solid line).