P.Y. Bourgeois

Ultra-low-noise microwave extraction from fiber-based optical frequency comb

In conclusion, we have used two FOFC based optical to microwave division frequency synthesizers referenced to a common optically source to create 11.55 GHz microwave signals with a relative frequency stability of 1.6×10-16 at 1 s. The relative phase noise spectral density at a 1 Hz offset from the 11.55 GHz carrier is measured at 111 dBrad2/Hz, limited by the readout system noise floor. Long term stability and accuracy down to 3×10-19 at 65536 s was also demonstrated from a set of 3 days continuous measurement. These results are obtained with classical double balanced mixers measurement scheme. By using a noise measurement system based on the carrier suppression method and advanced noise reduction techniques we are able to improve the results down to a phase noise spectral density at a 1 Hz of 117 dBrad2/Hz and a FFS is of 1.5×10-19 at 1000s (for a single system).

ELISA: A cryocooled 10 GHz oscillator with 10−15 frequency stability

This article reports the design, the breadboarding, and the validation of an ultrastable cryogenic sapphire oscillator operated in an autonomous cryocooler. The objective of this project was to demonstrate the feasibility of a frequency stability of 3x10(-15) between 1 and 1000 s for the European Space Agency deep space stations. This represents the lowest fractional frequency instability ever achieved with cryocoolers. The preliminary results presented in this paper validate the design we adopted for the sapphire resonator, the cold source, and the oscillator loop.

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.

A cryogenic open-cavity sapphire reference oscillator with low spurious mode density

In this paper, we describe the implementation of a microwave cryogenic sapphire oscillator (CSO) at the Laboratoire de Physique et Metrologie des Oscillateurs. In our realization we solved the problem of the spurious modes by operating the sapphire resonator in an open cavity. The CSO compared to a hydrogen maser demonstrates a frequency stability better than 3/spl times/10/sup -14/ at short term. Its long-term frequency instability of the order of 3/spl times/10/sup -12/ / day is limited by a random walk process. A first attempt to use this reference oscillator to characterize other signal sources is presented.

New-generation of cryogenic sapphire microwave oscillators for space, metrology, and scientific applications

We recently demonstrated a Cryogenic Sapphire Oscillator (CSO) presenting a short term frequency stability better than 3 × 10⁻¹⁵ for 1 s≤ τ < 1000 s and achieving 4.5 × 10⁻¹⁵ for one day integration. This CSO incorporates a pulse-tube cooler instead of a bath cryostat-thus eliminating the need for regular supplies and manual transferring of liquid helium. The advent of reliable and cryocooled CSO open the possibility to implement such an ultra-stable reference not only in metrological laboratories with liquid helium facilities but also in remote sites like base stations for space navigation, VBLI antenna sites, …

Simple model for the mode-splitting effect in whispering-gallery-mode resonators

In this paper, we present a model describing the mode-splitting effect in a whispering-gallery (WG)-mode resonator. The WG mode is represented by an equivalent transmission-line ring resonator in which a localized perturbation is introduced. This perturbation induces a coupling between the two counter propagating waves, which, in turn, lifts the degeneracy of the WG modes. This simple model explains almost all the line shapes experimentally observed. It shows in a straightforward way how the coupling on the two twin modes are affected by changing the coupling probe and the perturbation angular positions. In that sense, it is useful to make the resonator adjustment easier. Moreover, the same approach can be used to simulate any microstrip ring resonator with localized perturbation.

Use of erythropoietin for bloodless surgery in a Jehovah's witness infant.

Summary We present a case of surgery in a 2‐month‐old infant of the Jehovahs Witness (JW) faith weighing 2.8 kg scheduled for left upper lobectomy because of congenital lobar emphysema. He presented with physiological anaemia (haematocrit 33.8%) in accordance with his age. Because of the relative emergency of surgery, a short erythropoietin course was instituted. Recombinant human erythropoietin (rHuEPO) at a dosage of 180 U·kg−1·day−1 was administered for 10 days preoperatively and for 4 days postoperatively. Iron was administered orally and intravenously over the entire perioperative period. No side‐effects from either erythropoietin or intravenously administered iron were observed. To our knowledge, this is the first case published of a short perioperative rHuEPO course in an infant.

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.

Amplification process in a high-Q cryogenic whispering gallery mode sapphire Fe3 + maser

This paper reports on the analysis of a high-Q (109) cryogenic whispering gallery mode (WGM) sapphire resonator maser oscillator based on residual impurities of the Fe3 + ion (1 ppm). A theoretical model is developed to determine the evolution of the maser output power versus the pump power and the resonator output coupling coefficient. Comparison of the theoretical model and experimental data shows a good agreement.

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This paper introduces the Ω counter, a frequency counter-i.e., a frequency-to-digital converter-based on the linear regression (LR) algorithm on time stamps. We discuss the noise of the electronics. We derive the statistical properties of the Ω counter on rigorous mathematical basis, including the weighted measure and the frequency response. We describe an implementation based on a system on chip, under test in our laboratory, and we compare the Ω counter to the traditional Π and Λ counters. The LR exhibits the optimum rejection of white phase noise, superior to that of the Π and Λ counters. White noise is the major practical problem of wideband digital electronics, both in the instrument internal circuits and in the fast processes, which we may want to measure. With a measurement time τ, the variance is proportional to 1/τ2 for the Π counter, and to 1/τ3 for both the Λ and Ω counters. However, the Ω counter has the smallest possible variance, 1.25 dB smaller than that of the Λ counter. The Ω counter finds a natural application in the measurement of the parabolic variance, described in the companion article in this Journal [vol. 63 no. 4 pp. 611-623, April 2016 (Special Issue on the 50th Anniversary of the Allan Variance), DOI 10.1109/TUFFC.2015.2499325].