N. Bazin

Maser Oscillation in a Whispering-Gallery-Mode Microwave Resonator

We report the observation of above-threshold maser oscillation in a whispering-gallery (WG)-mode resonator, whose quasitransverse-magnetic, 17th-azimuthal-order WG mode, at a frequency of approximately 12.038GHz, with a loaded Q of several hundred million, is supported on a cylinder of monocrystalline sapphire. An electron spin resonance associated with Fe3+ ions, that are substitutively included within the sapphire at an effective concentration of a few parts per billion, coincides in frequency with that of the (considerably narrower) WG mode. By applying a cw “pump” to the resonator at a frequency of approximately 31.34GHz, with no applied dc 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 100s.

MASER OSCILLATION FROM ELECTRONIC SPIN RESONANCE IN A CRYOGENIC SAPPHIRE FREQUENCY STANDARD

We report the first observation of an Fe3+ maser oscillation at zero magnetic field inside a whispering gallery (WG) sapphire resonator. The described maser is new in that it operates at zero-field and with low ion concentration. At zero-field, the Fe3+ ion shows a 3-level structure related to the electron spin resonance (ESR). By applying a 31 GHz pump (|1/2〉 → |5/2〉), the ion operates as a maser at 12 GHz (|5/2〉 → |3/2〉). The maser effect is made possible by the high Q-factor (several 108) of the cryogenic whispering gallery resonator. Additionnaly, the sharp cavity resonance provides short term stability. Preliminary measurements indicate a frequency stability of parts in 10-14 (Allan deviation at 100 s), still limited by the instrument. The ultimate maser stability is still unknown.

Sapphire resonators + SiGe transistors based ultra low phase noise microwave oscillators

This paper reports on ultra-low phase noise microwave oscillators combining a room temperature high-Q whispering gallery mode (WGM) sapphire resonator and an ultra-low phase noise SiGe HBT based amplifier. An original symmetrical duralumin cavity has been designed in order to improve the thermal behavior of the resonator. Coupled to a high-precision electronic temperature controller, the structure presents a sensitivity to thermal fluctuations of -0.05 ppm/K. The non-linear and noise modelling of different microwave SiGe amplifiers have been realized in order to compute and optimize their phase noise performances. An original double stage amplifier, whose phase noise performances are very close of those of a single stage one, has been designed for X-band applications. C-band oscillators phase noise as low as -42 dB.rad2.Hz1at 1 Hz Fourier frequency and -135 dB.rad2.Hz1 at 1 kHz offset have been measured. X-band oscillators simulated phase noise results foresee very encouraging results

Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe3+ ions in a high-Q whispering gallery mode sapphire resonator

We report observations of the gyrotropic change in magnetic susceptibility of the Fe 3+ electron paramagnetic resonance at 12.037GHz (between spin states|1/2 > and |3/2 >) in sapphire with respect to applied magnetic field. Measurements were made by observing the response of the high-Q Whispering Gallery doublet (WGH±17,0,0) in a Hemex sapphire resonator cooled to 5 K. The doublets initially existed as standing waves at zero field and were transformed to traveling waves due to the gyrotropic response.

ELISA: An ultra-stable oscillator for esa deep space antennas

The technology of the Sapphire Whispering Gallery Mode Resonator allows to surpass the frequency stability of traditional ultra-stable oscillators, and then can be exploited in number of applications requiring a high frequency stability as a frequency standard for the ESA ground station for which the requirement in term of frequency stability is σ<inf>y</inf>(τ) = 3 × 10⁻¹⁵ for integration times 1 ≤ τ ≤ 1000s.

New Temperature Compensated Sapphire-Rutile Resonator Oscillator

The paper presents the characterization of a new microwave temperature compensated sapphire-rutile resonator oscillator. The oscillator frequency instability performances are better than 2 times 10-13 for tau < 1000s, and the frequency drift is estimated at 2.5 times10-12/day. These medium and long term results constitute, up to now, the state of the art for microwave temperature compensated sapphire resonator oscillator

Study of paramagnetic properties of Fe3+ ions to realizing Whispering Gallery Maser Oscillator

In a preceding publication, we reported the experimental demonstration of maser oscillation at 12.04 GHz in a cryogenic sapphire whispering-gallery-mode resonator, where the resonators dielectric ring contained a low concentration of paramagnetic Fe3+ ions within its monocrystalline sapphire lattice. Our preliminary measurements revealed a frequency stability of the order of 2.5 times 10-14 in a non-optimized design. In this paper, we report new measurements made on this same resonator to determine more precisely the main parameters affecting the dynamics of the Fe3+ ions when exposed to a microwave signal within their ESR bandwidth

Titanium doped cryogenic sapphire resonator oscillators

Residual paramagnetic impurities are present in high quality sapphire crystal. This phenomenon was exploited as paramagnetic spin compensation at liquid helium temperature to build high Q cryogenic sapphire resonator oscillators (CSRO). In this paper we present the characterization of intentionally Ti3+ and Ti4+ doped sapphire resonator oscillators. For the Ti3+ resonator we used the 12.7 GHz mode operating at 34K. This resonator exhibited a frequency stability of order 2 times 10-3 for 8s < tau < 20s with the use of a Gifford-McMahon cryocooler as a cold source. This corresponds to state-of-the-art line splitting of the order of 10 -7. A second experiment with a pulse tube cryocooler shows an improvement in the short term frequency stability. The Ti4+ resonator oscillator at 13.8 GHz exhibited a frequency stability of 7 times 10-14 at tau = 16s

High stability Cryocooled 10 GHz oscillator for the European Space Agency

This paper reports on a 10 GHz ultra-stable Cryocooled Sapphire Oscillator (CSO) developed for the European Space Agency. This CSO presents a frequency stability better than 3 × 10⁻¹⁵ between 1 s and 1,000 s and a phase noise lower than −100 dBc/Hz at 1 Hz.

Observation of a bimodal behavior in a Whispering Gallery mode maser oscillator

We report in this paper the first observation of bimodal maser operation in a whispering gallery (WG) mode oscillator. The characteristics of the maser are discussed under operation in both the single and bimodal regimes. A stability measurement of the difference frequency between the maser doublet signals revealed operation for the first time at the fundamental thermal noise limit of the maser.