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Endogenous autofluorescence of biological tissues is an important source of information for biomedical diagnostics. Despite the molecular complexity of biological tissues, the list of commonly known fluorophores is strictly limited. Still, the question of molecular sources of the red and near-infrared excited autofluorescence remains open. In this work we demonstrated that the oxidation products of organic components (lipids, proteins, amino acids, etc.) can serve as the molecular source of such red and near-infrared excited autofluorescence. Using model solutions and cell systems (human keratinocytes) under oxidative stress induced by UV irradiation we demonstrated that oxidation products can contribute significantly to the autofluorescence signal of biological systems in the entire visible range of the spectrum, even at the emission and excitation wavelengths higher than 650 nm. The obtained results suggest the principal possibility to explain the red fluorescence excitation in a large class of biosystems&mdash, aggregates of proteins and peptides, cells and tissues&mdash, by the impact of oxidation products, since oxidation products are inevitably presented in the tissue. The observed fluorescence signal with broad excitation originated from oxidation products may also lead to the alteration of metabolic imaging results and has to be taken into account.

International audience; To improve the quality of optical resonator's fabrication, an important step consists in performing an annealing process up to 600°C. It improves the roughness of resonator's surface down to the nanometer scale. Concretely it helps in reducing stresses at the periphery of their surface thus allowing higher Q-factors. Mechanical treatments enable state-of-the art characteristics for the surface roughness. The design of an oven strongly depends on its ability to reach the desired annealing process. It is significantly improved thanks to nichrome resistant alloy wires and special chopped basalt fibers for thermal isolation. In addition to the experimental tests, and in order to get better understanding of the residual stresses inside the resonator, we have simulated the heating process in the oven using the finite element code ANSYS© and CFD fluid module. Thermal distribution at different times of the heating and for three different temperatures with the range of 600°C are described.

International audience; To obtain high quality factor optical resonators, we must reduce stresses at the periphery of their surface as mechanical treatments enable state-of-the art characteristics for the surface roughness. This process is driven by electronics significantly improved thanks to electronic boards based on the use of intensity pulses, coupled with feedback on several parameters for fitting the specific profile of the heating cycle. Sensor is based on K-type technology to reach specification up to 1000°C. Technology is based on the use of microcontroller, low noise operational amplifiers, field effect transistors and driven by a intensity signal.

Thermal annealing performed during process improves the quality of the roughness of optical resonators reducing stresses at the periphery of their surface thus allowing higher Q-factors. After a preliminary realization, the design of the oven and the electronic method were significantly improved thanks to nichrome resistant alloy wires and chopped basalt fibers for thermal isolation during the annealing process. Q-factors can then be improved.

3 p.; International audience; The configuration of the phase noise measurement system operating in the X-band (8.2-12.4 GHz) using a photonic delay line as a frequency discriminator is presented in this paper. This system does not need any excellent frequency reference and works for any frequency in this band. Oscillator frequency fluctuation is converted into phase frequency fluctuation through the delay line. The measured phase noise includes the device under test noise and the instrument background. Then the use of a cross correlation decreases the cross spectrum terms of uncommon phase noise as √(1/m), where m is the average number. Using cross correlation on 500 averages, the noise floor of the instrument £(f) becomes, respectively, −150 and −170 dBc Hz−1 at 10^1 and 10^4 Hz from the 10 GHz carrier (−90 and −170 dBc Hz−1 including 2 km delay lines). We then focus on determining the uncertainty. There are two categories of uncertainty terms: 'type A', statistic contributions such as repeatability and experimental standard deviation; 'type B' due to various components and temperature control. The elementary term of uncertainty for repeatability is found to be equal to 0.68 dB. Other elementary terms still have lower contributions. This leads to a global uncertainty of 1.58 dB at 2σ.

International audience; The performance advances in communication systems like Radar system, precision navigation, space application and time and frequency metrology require more stable frequency and low phase noise system. Here is presented a configuration of phase noise measurement system operating in X-band using a photonic delay line as a frequency discriminator. This system doesn't need any excellent frequency reference and works for any frequency between 8.2 and 12.4 GHz. Using cross correlation on 500 averages, noise floor of the instrument is respectively -150 and -170 dBc/Hz at 10(1) and 10(4) Hz from the 10 GHz carrier (-90 and -170 dBc/Hz including 2 km delay lines). This instrument is developed in the context of association with the national french metrology institute (laboratoire national de metrologie et d'essais, LNE). This calibration system is to be integrated in measurements means of the accredited laboratory to improve the Calibration Metrology Capabilities (CMC) of the LNE.