Strong Coupling between Whispering Gallery Modes and Chromium Ions in Ruby

Abstract

We report the study of interactions between cavity photons and paramagnetic Cr${}^{3+}$ spins in a ruby (Cr${}^{3+}$:Al${}_2$O${}_3$) Whispering Gallery mode (WGM) resonator. Examining the system at microwave frequencies and millikelvin temperatures, spin-photon couplings up to 610 MHz or about 5% of photon energy are observed between the impurity spins and high quality factor ($Q>10^5$) WGM. Large tunability and spin-spin interaction allows operation in the strong coupling regime. The system exhibits behaviour not predicted by the usual Tavis-Cummings model because of interactions within the two-level spin bath, and the existence of numerous photonic modes.

References in corpus (6)

• Circuit cavity electromechanics in the strong coupling regime
• Strong magnetic coupling of an ultracold gas to a superconducting waveguide cavity
• Anisotropic rare-earth spin ensemble strongly coupled to a superconducting resonator
• Cavity QED with an ultracold ensemble on a chip: prospects for strong magnetic coupling at finite temperatures
• Spin-Photon Interaction in a Cavity with Time-Reversal Symmetry Breaking
• Hybrid Electron Spin Resonance and Whispering Gallery Mode Resonance Spectroscopy of Fe3+ in Sapphire