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.

The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special conditions, have been analyzed in different geometries and settings. Nevertheless, they are still awaiting experimental demonstration. The most important advances in this topic are briefly discussed in this review, pointing out aspects that have not been clearly covered by the literature. Finally, the existence of these surface waves in specific material examples is analyzed, discussing the challenge posed by their experimental observation.

High aspect ratio free-standing Al-doped ZnO (AZO) nanopillars and nanotubes were fabricated using a combination of advanced reactive ion etching and atomic layer deposition (ALD) techniques. Prior to the pillar and tube fabrication, AZO layers were grown on flat silicon and glass substrates with different Al concentrations at 150-250 °C. For each temperature and Al concentration the ALD growth behavior, crystalline structure, physical, electrical and optical properties were investigated. It was found that AZO films deposited at 250 °C exhibit the most pronounced plasmonic behavior with the highest plasma frequency. During pillar fabrication, AZO conformally passivates the silicon template, which is characteristic of typical ALD growth conditions. The last step of fabrication is heavily dependent on the selective chemistry of the SF₆ plasma. It was shown that silicon between AZO structures can be selectively removed with no observable influence on the ALD deposited coatings. The prepared free-standing AZO structures were characterized using Fourier transform infrared spectroscopy (FTIR). The restoration of the effective permittivities of the structures reveals that their anisotropy significantly deviates from the effective medium approximation (EMA) prognoses. It suggests that the permittivity of the AZO in tightly confined nanopillars is very different from that of flat AZO films.

We report the first experimental demonstration of anomalous breakdown of the effective medium approximation in all-dielectric deeply subwavelength thickness ($d\sim \lambda /160-\lambda /30$) multilayers, as recently predicted theoretically [H. H. Sheinfux et al., Phys. Rev. Lett. 113, 243901 (2014)]. Multilayer stacks are composed of alternating alumina and titania layers fabricated using atomic layer deposition. For light incident on such multilayers at angles near the total internal reflection, we observe pronounced differences in the reflectance spectra for structures with 10- vs 20-nm thick layers, as well as for structures with different layers ordering, contrary to the predictions of the effective medium approximation. The reflectance difference can reach values up to 0.5, owing to the chosen geometrical configuration with an additional resonator layer employed for the enhancement of the effect. Our results are important for the development of new high-precision multilayer ellipsometry methods and schemes, as well as in a broad range of sensing applications.

The photonic spin Hall effect in transmission is a transverse beam shift of the out-coming beam depending on polarization of the incoming beam. The effect can be significantly enhanced by materials with high anisotropy. We report, to the best of our knowledge, the first experimental demonstration of the photonic spin Hall effect in a multilayer hyperbolic metamaterial at visible wavelengths (wavelengths of 520 and 633 nm). The metamaterial is composed of alternating layers of gold and alumina with deeply subwavelength thicknesses, exhibiting extremely large anisotropy. The angle-resolved polarimetric measurements showed the shift of 165 μm for the metamaterial of 176 nm in thickness. Additionally, the transverse beam shift is extremely sensitive to the variations of the incident angle changing theoretically by 270 μm with 1 milli-radian (0.057°). These features can lead to minituarized spin Hall switches and filters with high angular resolution.