Electromagnetic surface waves guided by the planar interface of an isotropic dielectric medium and a uniaxial dielectric medium, both non-dissipative, were considered, the optic axis of the uniaxial medium lying in the interface plane. Whereas this interface is known to support the propagation of Dyakonov surface waves when certain constraints are satisfied by the constitutive parameters of the two partnering mediums, we identified a different set of constraints that allow the propagation of surface waves of a new type. The fields of the new surface waves, named Dyakonov–Voigt (DV) surface waves, decay as the product of a linear and an exponential function of the distance from the interface in the anisotropic medium, whereas the fields of the Dyakonov surface waves decay only exponentially in the anisotropic medium. In contrast to Dyakonov surface waves, the wavenumber of a DV surface wave can be found analytically. Also, unlike Dyakonov surface waves, DV surface waves propagate only in one direction in each quadrant of the interface plane.

The canonical boundary-value problem for surface-plasmon-polariton (SPP) waves guided by the planar interface of a dielectric material and a plasmonic material was solved for cases wherein either partnering material could be a uniaxial material with optic axis lying in the interface plane. Numerical studies revealed that two different SPP waves, with different phase speeds, propagation lengths, and penetration depths, can propagate in a given direction in the interface plane; in contrast, the planar interface of isotropic partnering materials supports only one SPP wave for each propagation direction. Also, for a unique propagation direction in each quadrant of the interface plane, it was demonstrated that a new type of SPP wave -called a surface-plasmon-polariton-Voigt (SPP-V) wave -can exist. The fields of these SPP-V waves decay as the product of a linear and an exponential function of the distance from the interface in the anisotropic partnering material; in contrast, the fields of conventional SPP waves decay only exponentially with distance from the interface. Explicit analytic solutions of the dispersion relation for SPP-V waves exist and help establish constraints on the constitutive-parameter regimes for the partnering materials that support SPP-V-wave propagation. * E-mail: T.Mackay@ed.ac.uk. arXiv:1907.07211v2 [physics.optics] 4 Sep 2019 readily achieved indirectly via coupling with a prism [2][3][4] or surface-relief grating [5], for examples. SPP waves are of major technological importance: they have been widely exploited for optical sensing [5-7] and microscopy [8,9], and applications for optical communications [10][11][12][13][14] and harvesting solar energy [15][16][17] are on the horizon.The theory underpinning SPP-wave propagation is firmly established in the case where the two partnering materials are isotropic [1]. The case where an isotropic plasmonic material is partnered with an anisotropic dielectric material has also been considered previously [18][19][20]. However, SPP-wave propagation in the case where an anisotropic plasmonic material is partnered with an isotropic dielectric material has received scant attention from theorists, even though several experimental studies on this case have been reported recently [21][22][23][24][25][26].As we demonstrate in this paper, when anisotropic partnering materials are involved, some previously unreported SPP-wave characteristics emerge. Most notably, two different SPP waves, with different phase speeds, propagation lengths, and propagation depths, can propagate in a given direction in the interface plane. Analogously, this multiplicity of surface waves can also arise in the case of Dyakonov-wave propagation supported by dissipative anisotropic materials [27], and has also been reported in the case of SPP-wave propagation supported by periodically nonhomogeneous dielectric materials [28,29].Additionally, we demonstrate that when anisotropic partnering materials are involved, for a unique propagation direction in each quadrant of the interface plane...

Dyakonov-Voigt (DV) surface waves guided by the planar interface of (i) material A which is a uniaxial dielectric material specified by a relative permittivity dyadic with eigenvalues ε s A and ε t A , and (ii) material B which is an isotropic dielectric material with relative permittivity ε B , were numerically investigated by solving the corresponding canonical boundary-value problem. The two partnering materials are generally dissipative, with the optic axis of material A being inclined at the angle χ ∈ [0 • , 90 • ] relative to the interface plane. No solutions of the dispersion equation for DV surface waves exist when χ = 90 • . Also, no solutions exist for χ ∈ (0 • , 90 • ), when both partnering materials are nondissipative. For χ ∈ [0 • , 90 • ), the degree of dissipation of material A has a profound effect on the phase speeds, propagation lengths, and penetration depths of the DV surface waves. For mid-range values of χ, DV surface waves with negative phase velocities were found. For fixed values of ε s A and ε t A in the upper-half-complex plane, DV surface-wave propagation is only possible for large values of χ when |ε B | is very small. *

The propagation of Dyakonov-Tamm (DT) surface waves guided by the planar interface of two nondissipative materials A and B was investigated theoretically and numerically, via the corresponding canonical boundary-value problem. Material A is a homogeneous uniaxial dielectric material whose optic axis lies at an angle χ relative to the interface plane. Material B is an isotropic dielectric material that is periodically nonhomogeneous in the direction normal to the interface. The special case was considered in which the propagation matrix for material A is non-diagonalizable because the corresponding surface wave -named the Dyakonov-Tamm-Voigt (DTV) surface wave -has unusual localization characteristics. The decay of the DTV surface wave is given by the product of a linear function and an exponential function of distance from the interface in material A; in contrast, the fields of conventional DT surface waves decay only exponentially with distance from the interface. Numerical studies revealed that multiple DT surface waves can exist for a fixed propagation direction in the interface plane, depending upon the constitutive parameters of materials A and B. When regarded as functions of the angle of propagation in the interface plane, the multiple DT surface-wave solutions can be organized as continuous branches. A larger number of DT solution branches exist when the degree of anisotropy of material A is greater. If χ = 0 • then a solitary DTV solution exists for a unique propagation direction on each DT branch solution. If χ > 0 • , then no DTV solutions exist. As the degree of nonhomogeneity of material B decreases, the number of DT solution branches decreases. For most propagation directions in the interface plane, no solutions exist in the limiting case wherein the degree of nonhomogeneity approaches zero; but one solution persists provided that the direction of propagation falls within the angular existence domain of the corresponding Dyakonov surface wave.