Maser oscillation in a whispering-gallery-mode microwave resonator

Abstract

We report the first observation of above-threshold maser oscillation in a whispering-gallery(WG)mode resonator, whose quasi-transverse-magnetic, 17 th -azimuthal-order WG mode, at a frequency of approx. 12.038 GHz, with a loaded Q of several hundred million, is supported on a cylinder of mono-crystalline sapphire. An electron spin resonance (ESR) associated with Fe 3+ ions, that are substitutively included within the sapphire at a concentration of a few parts per billion, coincides in frequency with that of the (considerably narrower) WG mode. By applying a c.w. 'pump' to the resonator at a frequency of approx. 31.34 GHz, with no applied d.c. magnetic field, the WG ('signal') mode is energized through a three-level maser scheme. Preliminary measurements demonstrate a frequency stability (Allan deviation) of a few times 10 −14 for sampling intervals up to 100 s.

Room-temperature solid-state maser

“…The active material within a conventional solid-state maser is a dielectric crystal containing paramagnetic ions, e.g. ruby, that is maintained typically below 10 K and exposed (with exceptions 8,13 ) to a strong d.c. magnetic bias field. Despite the inconvenience of these operating conditions, as well as competition from amplifiers based on cooled high-electron-mobility transistors (HEMTs) 15 , ruby masers retain a niche in deep-3…”

Four-Wave Mixing fromFe3+Spins in Sapphire

“…The experimental system consists of a cryogenic sapphire resonator-oscillator [22][23][24][25][26][27] as shown in Fig. 1(a).…”

“…FWM is an enabling process for both frequency comb generation and many quantum computing and metrology applications. Our system is further suited to these applications due to the extremely low dielectric loss tangent at millikelvin temperature, which persists even at single photon input power [21].The experimental system consists of a cryogenic sapphire resonator-oscillator [22][23][24][25][26][27] as shown in Fig. 1(a).…”

Influence of the electron spin resonance saturation on the power sensitivity of cryogenic sapphire resonators

“…The thermal compensation induced by the accidental paramagnetic impurities that substitute to Al 3+ is essential for the achievement of the highest frequency stability [5,6]. A high Q-factor microwave cryogenic resonator containing a small amount of Fe 3+ can also be used as the amplifying medium to design a zero-field solid-state 12 GHz Maser [7,8] or as the non-linear element for microwave third harmonic generation [9,10] Paramagnetic impurities in sapphire are also good candidates for the realization of quantum electrodynamics measurements [11].…”