Generation of Bimodal Solitons in a Sapphire Whispering Gallery Mode Maser at Millikelvin Temperatures

Abstract

We present experimental observations of bimodal solitons in a solid state three-level maser cooled to millikelvin temperatures. The maser is built on a highly dilute ${\text{Fe}}^{3+}$ spin ensemble hosted by a high purity ${\text{Al}}_2{\text{O}}_3$ crystal constituting a high quality factor whispering-gallery-mode resonator. The maser is pumped through one of these modes, near 31 GHz, generating two signals near 12.04 GHz from two distinct modes, 8 MHz apart. The system demonstrates three regimes, namely, a continuous wave regime, a dense soliton regime and a sparse soliton regime. These results open new avenues for studying nonlinear wave phenomena using microwave systems as well as new applications of solitons in this part of the electromagnetic spectrum.

arXiv comment13 pages, 12 figures

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