Zero-Field Fe3+:Sapphire Whispering-Gallery-Mode Solid-State MASER Oscillator

P.Y. Bourgeois, M. Oxborrow, M.E. Tobar, N. Bazin, Y. Kersalé, K. Benmessaï, V. Giordano

Abstract: We report the realization of a new type of solid-state maser oscillator whose output frequency is controlled by a whispering-gallery (WG) electromagnetic mode. Here, the maser oscillator can be regarded as a free-running loop oscillator whose component loop resonator and sustaining amplifier are consolidated within the same compact object, namely a cylinder of Fe3+-doped mono-crystalline sapphire. This cylinder supports a 17th-azimuthal-order quasi-transverse-magnetic WG mode at approx. 12.04 GHz, with a loaded (ESR-saturated) Q of several hundred million. The WG mode’s frequency lies within the line-width of the electron spin resonance (ESR) associated with transitions between the lowest two paramagnetic levels of Fe3+ ions, that are included within the sapphire’s lattice at a substitutive concentration of approx. one part per billion. By applying an auxiliary microwave ‘pump’ at a frequency of approx. 31.3 GHz to the resonator, a population inversion is achieved across this ‘signal’ ESR transition with no applied d.c. magnetic bias field. Despite the extremely low concentration of Fe3+ ions present, continuous above-threshold maser oscillation is achieved on the 12.04-GHz whispering-gallery mode due to its high Q. The power of the maser oscillator’s signal output exceeds -50 dBm, some 104 times greater than that provided by an active hydrogen maser. In a highly preliminary experiment, the oscillator’s frequency stability at 30 seconds was measured to be 2.5×10-14.
Published in: Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting
August 29 - 31, 2005
Vancouver, Canada
Pages: 355 - 362
Cite this article: Bourgeois, P.Y., Oxborrow, M., Tobar, M.E., Bazin, N., Kersalé, Y., Benmessaï, K., Giordano, V., "Zero-Field Fe3+:Sapphire Whispering-Gallery-Mode Solid-State MASER Oscillator," Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting, Vancouver, Canada, August 2005, pp. 355-362.
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