Broadband energy squeezing and tunneling based on unidirectional modes

TL;DR

This paper demonstrates broadband energy squeezing and tunneling using unidirectional modes in YIG-based waveguides, enabling efficient EM wave control at microwave frequencies with potential for advanced optical devices.

Contribution

It introduces a novel approach for broadband energy squeezing and tunneling based on unidirectional modes, overcoming limitations of previous resonance-based methods.

Findings

Achieved broadband energy squeezing and tunneling in YIG-based waveguides.

Demonstrated effective EM wave tunneling in highly bent structures.

Validated results with theoretical analysis and finite element simulations.

Abstract

Energy squeezing attracts many attentions for its potential applications in electromagnetic (EM) energy harvesting and optical communication. However, due to the Fabry-Perot resonance, only the EM waves with discrete frequencies can be squeezed and, as far as we know, in the previous energy-squeezing devices, stringent requirements of the materials or the geometrical shape are needed. We note that the structures filled with epsilon-near-zero (ENZ) mediums as reported in some works can squeeze and tunnel EM waves at frequencies (e.g. plasma frequency). However, the group velocity is usually near zero which means few EM information travel through the structures. In this paper, low-loss energy squeezing and tunneling (EST) based on unidirectional modes were demonstrated in YIG-based one-way waveguides at microwave frequencies. According to our theoretical analysis and the simulations using finite element method, broadband EST was achieved and the EM EST was observed even for extremely bended structures. Besides, similar EM EST was achieved in a realistic three-dimensional remanence-based one-way waveguide as well. The unidirectional modes-based EST paving the way to ultra-subwavelength EM focusing, enhanced nonlinear optics, and designing numerous functional devices in integrated optical circuits such as phase modulator.