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Updated: May 17, 2026

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators
Published on: August 5, 2013
Frequency conversion in a high Q-factor sapphire whispering gallery mode resonator due to paramagnetic nonlinearity
Daniel L Creedon1, Karim Benmessai, Michael E Tobar
1ARC Centre of Excellence for Engineered Quantum Systems, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Austsralia. daniel.creedon@uwa.edu.au
Abstract:
Nonlinear frequency conversion is a well known and widely exploited family of effects in optics, often arising from a Kerr nonlinearity in a crystal medium. Here, we report high stability frequency conversion in the microwave regime due to a χ(3) nonlinearity in sapphire introduced by a dilute concentration of paramagnetic spins. First, we produce a high stability comb from two microwave fields at 12.029 and 12.037 GHz corresponding to two high Q-factor whispering gallery (WG) modes within the electron spin resonance bandwidth of the Fe3+ ion. The resulting comb is generated by a cascaded four-wave mixing effect with a 7.7 MHz repetition rate. Then, by suppressing four-wave mixing by increasing the threshold power, third harmonic generation is achieved in a variety of WG modes coupled to various species of paramagnetic ion within the sapphire.
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