Features of excited fields in a cavity resonator filled with a near-zero refractive index medium

Abstract

Background. Modern artificial media are capable of providing specially pointed electromagnetic parameters, such as a negative refractive index, or a near-zero refractive index. These properties are widely used in optics and photonics in the latest developments, as well as for microwave range elements and devices. For example, such media give the opportunity to supercouple waveguides with highly mismatched cross sections. The use of a filling medium with a near-zero refractive index can significantly affect resonant frequencies of cavity resonator and expand the operating ranges of microwave resonators.

Objectives. The aim of the work is a theoretical study of the influence of the parameters of a dispersion medium with a near-zero refractive index on the resonance frequencies of a microwave cavity resonator filled with such a medium, and on the characteristics of forced oscillations in a cavity resonator.

Materials and methods. The problem of forced electromagnetic fields in a cavity resonator with perfectly conducting walls, filled with a homogeneous isotropic medium with a dispersion, due to which its refractive index is close to zero in a certain frequency range, is solved using an Evolutionary Approach to Electromagnetics in the Time Domain. This approach allows the separation of temporal and spatial parts of the problem, which significantly facilitates the solution and provides obtaining analytical-numerical solutions in the case of filling the resonator with an arbitrary homogeneous medium with dispersion. We used a medium model previously proposed in the literature, the refractive index of which is close to zero in a certain frequency range, and one of the main considered issues of the work is how the properties of the medium affect the characteristics of a microwave cavity resonator and forced electromagnetic fields.

Results. Analytical-numerical solutions of evolutionary equations for a specific medium with a refractive index close to zero in a certain frequency range were obtained in the work. The characteristics of the filled resonator were obtained, and the influence of the medium parameters on the resonant frequencies of the filled resonator and the spectral composition of forced oscillations was observed.

Conclusion. The paper theoretically shows the possibility to expand the frequency characteristics and operating modes of cavity resonators due to specific filling, to significantly increase the operating frequency of the microwave resonator.