Frequency dependence of the group velocity of surface polaritons in a single-axle crystal of the Würcite type

Abstract

Background. Surface polaritons attract the attention of researchers and engineers for their unique properties and promising applications in the field of micro- and nanoelectronics. Such applications may include devices such as the transistor or even the polariton laser, as reported in the scientific literature. Aim. The paper analyzes the conditions for excitation of surface polaritons in a uniaxial crystal of the wurtzite type. The frequency dependence of the group velocity of surface polaritons is analyzed. Methods. The dispersion equation for surface polaritons in an anisotropic wurtzite-type crystal is found analytically by solving Maxwell’s equations and requiring that the boundary conditions for electromagnetic waves decreasing exponentially from the boundary be satisfied. Results. Aluminum nitride crystal AlN was chosen as the object of analysis. Possible frequencies of surface polaritons are found and it is shown that only the frequency Ω_1 = 844,84 cm^−1 satisfies all the conditions for the existence of surface polaritons. It is shown that in the region where a surface polariton exists, both the damping constants and the propagation parameters of surface polaritons increase. It is shown that the group velocity of a surface polariton decreases with increasing frequency. When the frequency reaches the value of the surface polariton frequency of the value Ω_1, the group velocity vanishes. Conclusion. The found decreasing frequency dependence of the surface polariton group velocity can be used in moderating devices based on polaritons.