Magnet-Free Nonreciprocal frequency conversion using Sequential Temporal modulation: Theory and Simulations

TL;DR

This paper introduces a magnet-free, nonreciprocal frequency conversion method using sequential temporal modulation, enabling unidirectional signal routing without magnetic materials or nonlinearities.

Contribution

It presents a novel temporal sequencing scheme for frequency conversion that achieves nonreciprocity through fixed order interactions in a three-mode system.

Findings

Derived a compact analytical expression for isolation ratio.

Confirmed results with time-domain simulations across various parameters.

Provided practical design rules for optimizing nonreciprocity.

Abstract

Nonreciprocal conversion is essential for protecting sources and enabling unidirectional signal routing in photonic, phononic, electronics, and quantum systems, yet conventional implementations rely on magnetic bias that could be challenging to integrate on chip. We propose a magnet-free scheme for frequency-domain nonreciprocity based on sequential, time-gated couplings in a three-mode system. By activating interactions in a fixed temporal order, the forward and reverse frequency conversion pathways acquire unequal dwell times in a lossy intermediate mode, producing strong nonreciprocity without requiring nonlinearities or magnetic materials. Using a harmonic-balance formulation and a Dyson-Born expansion, we derive a compact analytical expression for the isolation ratio that reveals the roles of Floquet sidebands, duty-cycle control, modulation frequency, and dissipation. The results are confirmed by direct time-domain simulations over a wide parameter range. From these results, we extract practical design rules for optimizing isolation through temporal sequencing, loss engineering, and modulation timing. The framework is general and directly applicable to integrated platforms in photonics, phononics, microwave electronics, and superconducting circuits.