We report on a new accurate investigation tool whose principle is that of a Michelson interferometer with a broadband source, namely a phase-sensitive optical low-coherence interferometer, used to interrogate an optical micro-resonator based sensor for label-free biosensing applications. This set-up, which is able to provide the amplitude and also the phase of the guided mode in a single measurement, is also used to evaluate the performances of the micro-resonators. The best vertically coupled polymer racetrack micro-resonator fabricated displays a Q-factor higher than 38 000 and a finesse of 21 at 1527.7 nm when immersed in deionized water. The association of the phase-sensitive optical low coherence interferometer and the vertically coupled polymer micro-resonator in an opto-fluidic cell for biosensing applications was tested and allowed the detection of a concentration of glucose in water solution around 0.23 mg ml−1.
We describe picosecond single- and multiple-beam measurements of the nonlinear absorption and refraction in a variety of semiconductors. Single-beam and pump-probe transmission measurements are used to isolate instantaneous nonlinearities from cumulative processes. These techniques, together with a simple rate equation model, have allowed us to extract information regarding mid-gap levels and to measure both the two-photon absorption coefficients and the free carrier absorption cross sections in these samples. Our model, together with Z-scan and beam deflection measurements of the nonlinear refraction, has provided the change in index due to each photogenerated electron-hole pair.
Abstract. The reliable quantification of ultraviolet (UV) radiation at the Earth's surface requires accurate measurements of spectral global solar UV irradiance in order to determine the UV exposure to human skin and to understand long-term trends in this parameter. Array spectroradiometers are small, light, robust and cost effective instruments and are increasingly used for spectral irradiance measurements. Within the European EMRP-ENV03 project "Solar UV", new devices, guidelines, and characterization methods have been developed to improve solar UV measurements with array spectroradiometers and support to the end-user community has been provided. In order to assess the quality of 14 end-user array spectroradiometers, a solar UV intercomparison was held on the measurement platform of the World Radiation Center (PMOD/WRC) in Davos, Switzerland, from 10 to 17 July 2014. The results of the intercomparison revealed that array spectroradiometers, currently used for solar UV measurements, show a large variation in the quality of their solar UV measurements. Most of the instruments overestimate the erythema weighted UV index – in particular at low solar zenith angles – due to stray light contribution in the UV-B range. The spectral analysis of global solar UV irradiance further supported the finding that the uncertainties in the UV-B range are very large due to stray light contribution in this wavelength range. In summary, the UV index may be detected by some commercially available array spectroradiometer within 5 % compared to the world reference spectroradiometer, if well characterized and calibrated, but only for a limited range or solar zenith angle. Generally, the tested instruments are not yet suitable for solar UV measurements for the entire range between 290 to 400 nm under all atmospheric conditions.
The French Laser Megajoule (LMJ) is designed and constructed by the French Commissariat à l'Energie Atomique (CEA). Its amplifying section needs highly reflective multilayer mirrors for the flash lamps. To monitor and improve the coating process, the reflectors have to be characterized to high accuracy. The described spectrophotometer is designed to measure normal specular reflectance with high repeatability by using a small spot size of 100 mum. Results are compared with ellipsometric measurements. The instrument can also perform spatial characterization to detect coating nonuniformity.
An intercomparison of terrestrial photovoltaic (PV) calibrations was performed among a number of European calibration and testing laboratories that participated in the European Metrology Research Program (EMRP) project “PhotoClass”. The purpose of this intercomparison was to evaluate the comparability of calibration and testing services within the stated uncertainties of the individual laboratories. The calibration objects were two world photovoltaic scale (WPVS)-type reference solar cells, one made from crystalline silicon and one made from GaAs. The calibration value (CV) was the short-circuit current under standard test conditions ( I STC ). In conclusion, it was found that the CVs are all consistent within the stated uncertainties. This result strengthens the reliance in the calibration chain and in the PV calibration infrastructure in Europe.
A new optical reference technique for biosensing applications is proposed. An association of a biosensor, based on a polymer planar cyclic microresonator vertically coupled to a straight waveguide, with a phase-sensitive optical low-coherence interferometer, based on two Michelson interferometers, is described. Such a technique gives information in the spatial and the spectral domains. The theory and the first measurements on biological molecules are presented. The results show that the proposed technique is relevant for biosensing since the concentration detection limit meets already the expected needs.
An airborne imaging luminance-colorimeter is designed for aerial surveillance of specific geographic areas, typically 1000 km², at night-time. In addition to the measurement of the luminance [cd∙m-2], the instrument shall estimate colour temperatures, with 3000 K defined as the higher limit by the 2018’s French ministerial decree. The testing bench allows the luminance-colorimeter to be calibrated before the first operational flight. The bench presented here allows calibration in luminance, colour parameters, linearity, signal-to-noise ratio, geometrical distortion and vignetting. The instrument exhibits good spectral mismatch regarding the X1, X2, Y, and Z responses.
