About the role of phase matching between a coated microsphere and a tapered fiber: experimental study

nombre de pages 10International audienceCoatings of spherical optical microresonators are widely employed for different applications. Here the effect of the thickness of a homogeneous coating layer on the coupling of light from a tapered fiber to a coated microsphere has been studied. Spherical silica microresonators were coated using a 70SiO2 - 30HfO2 glass doped with 0.3 mol% Er3+ ions. The coupling of a 1480 nm pump laser inside the sphere has been assessed using a tapered optical fiber and observing the 1530-1580 nm Er3+ emission outcoupled to the same tapered fiber. The measurements were done for different coating thicknesses and compared with theoretical calculations to understand the relationship of the detected signal with the whispering gallery mode electric field profiles

High-resolution microwave frequency dissemination on an 86-km urban optical link

We report the first demonstration of a long-distance ultra stable frequency dissemination in the microwave range. A 9.15 GHz signal is transferred through a 86-km urban optical link with a fractional frequency stability of 1.3x10-15 at 1 s integration time and below 10-18 at one day. The optical link phase noise compensation is performed with a round-trip method. To achieve such a result we implement light polarisation scrambling and dispersion compensation. This link outperforms all the previous radiofrequency links and compares well with recently demonstrated full optical links.Comment: 11 pages, 5 figure

Whispering gallery modes in coated silica microspheres

6 pagesInternational audienceSilica microspheres were made by melting the tip of a standard telecom fiber and were coated with a 70SiO2 - 30 HfO2 sol-gel derived glass activated by 0.3 mol % of Er3+ ions. The samples were coated using a dip coating apparatus. The thickness of the coating was estimated to be around 1 μm. The whispering gallery modes of the coated resonator were studied using a full taper - microsphere coupling setup. Upon excitation at 1480 nm sharp peaks at wavelengths 1540- 1565 nm were observed. They were attributed to the whispering gallery modes of the microsphere falling in the wavelength range of the erbium emission

Low frequency noise characterization and modeling of microwave bipolar devices : application to the design of low phase noise oscillator

This paper addresses advanced low frequency noise measurements and modeling of SiGe HBTs. Results have been implemented into a nonlinear Gummel Poon model which has been validated through the design of a DRO made of an integrated SiGe negative resistance in the 10 GHz range. We have obtained phase noise of -105 dBc/Hz at 10 kHz offset, which is close to the state of the art, and we have demonstrated a design technique that provides an accurate phase noise prediction

Low frequency noise characterization and modeling of microwave bipolar devices: Application to the design of low phase noise oscillator

This paper addresses advanced low frequency noise measurements and modeling of SiGe HBTs. Results have been implemented into a non linear Gummel Poon model which has been validated through the design of a DRO made of an integrated SiGe negative resistance in the 10 GHz range. We have obtained phase noise of -105 dBc/Hz at 10 kHz offset, which is close to the state of the art, and we have demonstrated a design technique that provides an accurate phase noise prediction

Light Coupling Between the Whispering Gallery Modes of a Coated Microsphere and a Tapered Fiber

4 pagesInternational audienceSpherical microresonators were coated using a 70SiO2 - 30HfO2 glass doped with 0.3 mol% Er3+. The sphere was characterized by coupling a 1480 nm pump laser inside the sphere using a tapered optical fiber and observing the 1530-1580 nm Er3+ emission outcoupled with the same tapered fiber. The measurements were done for different coating thicknesses and compared with theoretical calculations to understand the relationship of the detected signal with the whispering gallery mode electric field profiles

Whispering gallery mode profiles in a coated microsphere

International audienceThe properties of whispering gallery modes (WGM) of a microsphere can be tailored by coating the resonator with a thin film. If the coating has a higher refractive index than the microsphere core, the resulting structure will have a configuration which has similarities both with a classical WGM resonator and with a planar waveguide. By choosing the film thickness and refractive index we can tailor the degree of confinement of the WGMs inside the sphere core, coating and surrounding medium, which will in turn influence the WGMs contact with its surroundings. We present a study of the effect of the coating on the WGM mode profiles in particular of a silicon coating on a silica sphere

Acute Cycling Exercise Induces Changes in Red Blood Cell Deformability and Membrane Lipid Remodeling

Here we describe the effects of a controlled, 30 min, high-intensity cycling test on blood rheology and the metabolic profiles of red blood cells (RBCs) and plasma from well-trained males. RBCs demonstrated decreased deformability and trended toward increased generation of microparticles after the test. Meanwhile, metabolomics and lipidomics highlighted oxidative stress and activation of membrane lipid remodeling mechanisms in order to cope with altered properties of circulation resulting from physical exertion during the cycling test. Of note, intermediates from coenzyme A (CoA) synthesis for conjugation to fatty acyl chains, in parallel with reversible conversion of carnitine and acylcarnitines, emerged as metabolites that significantly correlate with RBC deformability and the generation of microparticles during exercise. Taken together, we propose that RBC membrane remodeling and repair plays an active role in the physiologic response to exercise by altering RBC properties

Coated spherical microresonators for cutting-edge photonics application

Coated Spherical MicroresonatorsInternational audienceWe present some results regarding the coating of spherical microresonators and their different applications in photonics. The spherical microresonators high Q-factor and low mode volume make them perfect for a number of photonics applications. A thin film coating on the surface of the resonator using an optically active or passive layer can be used to modify signifactly the optical properties of the resonator. We have succesfully coated the microresonators with a sol-gel derived coating and have studied the effect of the coating on different optical and spectroscopical properties of the microresonator