John A. Polo

On the surface plasmon polariton wave at the planar interface of a metal and a chiral sculptured thin film

The solution of a dispersion equation indicates the theoretical existence of multiple modes of surface plasmon polariton wave propagation at the planar interface of a metal and a chiral sculptured thin film (STF). One mode appears to occur over a wide range of the structural period of the chiral STF, while all other modes exist only above some minimum value of the structural period, the minimum value being different for each mode. In order to excite the different modes, the interface can be incorporated in the commonplace Kretschmann configuration, for which our calculations show that the efficient excitation of different modes would require different numbers of structural periods of the chiral STF.

Dyakonov-Tamm wave at the planar interface of a chiral sculptured thin film and an isotropic dielectric material

Surface waves, named here as Dyakonov--Tamm waves, can exist at the planar interface of an isotropic dielectric material and a chiral sculptured thin film (STF). Due to the periodic nonhomogeneity of a chiral STF, the range of the refractive index of the isotropic material is smaller but the range of the propagation direction in the interface plane is much larger, in comparison to those for the existence of Dyakonov waves at the planar interface of an isotropic dielectric material and a columnar thin film.

Energy flux in a surface-plasmon-polariton wave bound to the planar interface of a metal and a structurally chiral material

The spatial profile of the energy flux in a surface-plasmon-polariton (SPP) wave bound to the planar interface of a metal and a structurally chiral material (SCM) shows strong dependencies on the pitch of the SCM. More than one SPP-wave mode at the same frequency (or free-space wavelength) being possible for the chosen interface, the energy-flux profiles of different modes are different. Although the energy flux on the metal side of the interface decays exponentially with distance from the interface, the profile on the SCM side exhibits oscillations as a function of distance from the interface and decay rates, which are highly variable. Because of the periodic nature of the SCM, the Floquet-Lyapunov theorem may be invoked to explain this behavior.

Propagation of surface waves at the planar interface of a columnar thin film and an isotropic substrate

Surface-wave propagation at the planar interface of a columnar thin film (CTF) -- a biaxial dielectric medium -- and an isotropic dielectric substrate may occur over a narrow range of propagation directions, range being dependent on (i) the bulk matgerial that is evaporated to deposit the CTF, (ii) the vapor incidence angle used for the deposition, and (iii) the refractive index of the substrate material.

Dyakonov-Tamm wave guided by a twist defect in a structurally chiral material

The boundary-value problem for a Dyakonov-Tamm wave guided by a twist defect in a structurally chiral material and propagating along the bisector of the twist defect was formulated. The resulting dispersion equation was numerically solved. Detailed analysis showed that either two or three different Dyakonov-Tamm waves can propagate, depending on the value of the twist angle. These waves have different phase speeds and degrees of localization to the twist-defect interface.

Surface waves with simple exponential transverse decay at a biaxial bicrystalline interface

The dispersion equation for surface waves--with simple transverse exponential decay at the interface of identical biaxial crystals with a relative twist about the axis normal to the interface and propagating along a bisector of the angle between the crystallographic configurations on either side of the interface--has several solutions of which only one is physical. The selected type of surface wave is possible only for a restricted range of the twist angle, which depends on the ratio of the maximum and the minimum of the principal refractive indexes and the angle between the optic ray axes.

Mapping multiple surface-plasmon-polariton-wave modes at the interface of a metal and a chiral sculptured thin film

We charted multiple surface-plasmon-polariton (SPP)-wave modes at the planar interface between a metal and a chiral sculptured thin film (STF) in terms of the period, vapor flux angle, and orientation angle of the latter material. Two distinct scenarios were considered: one based on a canonical boundary-value problem involving half-spaces filled with the metal and the chiral STF and another based upon a modified Kretschmann configuration for ease of implementation. Calculations using empirical data for the constitutive relations of both partnering materials show that the number and nature of the SPP-wave modes are highly dependent on all three parameters.

Surface waves at a biaxial bicrystalline interface

Localized to the planar interface of two identical dielectric biaxial crystals with optic ray axes parallel to the interface but with a relative twist about an axis perpendicular to the interface, electromagnetic wave propagation along the bisectrix of the two crystallographic orientations is possible with either real-valued or complex-valued transverse decay constants as the twist angle varies from 0 degrees to an upper limit (< or =90 degrees) that is dependent on the angle between the two optic ray axes.

Theory of Dyakonov–Tamm waves at the planar interface of a sculptured nematic thin film and an isotropic dielectric material

In order to ascertain the conditions for surface-wave propagation guided by the planar interface of an isotropic dielectric material and a sculptured nematic thin film (SNTF) with periodic nonhomogeneity, we formulated a boundary-value problem, obtained a dispersion equation therefrom, and numerically solved it. The surface waves obtained are Dyakonov–Tamm waves. The angular domain formed by the directions of propagation of the Dyakonov–Tamm waves can be very wide (even as wide as to allow propagation in every direction in the interface plane), because of the periodic nonhomogeneity of the SNTF. A search for Dyakonov–Tamm waves is, at the present time, the most promising route to take for experimental verification of surface-wave propagation guided by the interface of two dielectric materials, at least one of which is anisotropic. That would also assist in realizing the potential of such surface waves for optical sensing of various types of analytes infiltrating one or both of the two dielectric materials.

Dyakonov–Tamm waves guided by the planar interface of an isotropic dielectric material and an electro-optic ambichiral Reusch pile

The existence of an electromagnetic surface wave—classified as a Dyakonov–Tamm wave—guided by the planar interface of an isotropic, homogenous, dielectric material and an electro-optic ambichiral Reusch pile was theoretically established for various values of a dc electric field applied normal to the interface. For low magnitudes of the dc electric field, the spread of values of the refractive index ns of the isotropic partnering material supporting the surface waves is exceedingly small. A sufficient increase in the magnitude of the dc electric field considerably widens that range. The allowed propagation directions, in all cases, constitute an angular sector of several tens of degrees in width.