Realization of the unidirectional amplification in a cavity magnonic system

TL;DR

This paper demonstrates a nonreciprocal microwave amplifier using a cavity magnonic system, achieving unidirectional amplification and high isolation, with potential applications in quantum technology for signal amplification and noise isolation.

Contribution

The work introduces a novel cavity magnonic system that combines active feedback and nonreciprocity to realize unidirectional microwave amplification with high isolation.

Findings

Achieved 11.5 dB forward gain

Attenuated reverse signal by -34.7 dB

Isolation ratio of 46.2 dB

Abstract

We experimentally demonstrate the nonreciprocal microwave amplification using a cavity magnonic system, consisting of a passive cavity (i.e., the split-ring resonator), an active feedback circuit integrated with an amplifier, and a ferromagnetic spin ensemble (i.e., a yttrium-iron-garnet sphere). Combining the amplification provided by the active circuit and the nonreciprocity supported by the cavity magnonics, we implement a nonreciprocal amplifier with the functions of both unidirectional amplification and reverse isolation. The microwave signal is amplified by 11.5 dB in the forward propagating direction and attenuated in the reverse direction by -34.7 dB, giving an isolation ratio of 46.2 dB. Such a unidirectional amplifier can be readily employed in quantum technologies, where the device can simultaneously amplify the weak signal output by the quantum system and isolate the sensitive quantum system from the backscattered external noise. Also, it is promising to explore more functions and applications using a cavity magnonic system with real gain.