# Non-reciprocity using quadrature-phase time-varying slab resonators

## TL;DR

This paper demonstrates that non-reciprocity can be achieved in time-varying media using only two Fabry-Perot slabs with quadrature-phase periodic permittivities, without spatio-temporal modulation.

## Contribution

It introduces a novel approach to non-reciprocity using simple time-varying resonators and develops generalized transfer matrices and a coupled mode theory for analysis.

## Key findings

- Significant non-reciprocal transmission at the incident frequency.
- Analytical and simulation results are in excellent agreement.
- New modeling techniques for time-varying slab resonators.

## Abstract

In this paper, it is shown that non-reciprocity can be observed in time-varying media without employing spatio-temporal modulated permittivities. We show that by using only two one dimensional Fabry-Perot slabs with time-periodic permittivities having quadrature phase difference, it is possible to achieve considerable non-reciprocity in transmission at the incidence frequency. To analyze such scenario,generalized transfer matrices are introduced to find the wave amplitudes of all harmonics in all space. The results are verified by in-house FDTD simulations. Moreover, in order to have a simple model of such time-varying slab resonators, a time-perturbed coupled mode theory is developed for multiple resonances, and it is shown that the results obtained by this method and the analytical method are in excellent agreement.