Michel Cathelinaud

Photo-stability of pulsed laser deposited Ge(x)As(y)Se(100-x-y) amorphous thin films.

Quest for photo-stable amorphous thin films in ternary Ge(x)As(y)Se(100-x-y) chalcogenide system is reported. Studied layers were fabricated using pulsed laser deposition technique. Scanning electron microscope with energy dispersive X-ray analyzer, Raman scattering spectroscopy, transmittance measurements, variable angle spectroscopic ellipsometry, and non-linear imaging technique with phase object inside the 4f imaging system were employed to characterize prepared thin films. Their photo-stability/photo-induced phenomena in as-deposited and relaxed states were also investigated, respectively. In linear regime, we found intrinsically photo-stable relaxed layers within Ge(20)As(20)Se(60) composition. This composition presents also the highest optical damage threshold under non-linear optical conditions.

Optical modeling of organic solar cells based on CuPc and C60.

We have investigated the influence of the poly(3,4-ethylenedioxythiophene)-blend-poly(styrene-sulfonate) (PEDOT:PSS) layer on the short-circuit current density (J(sc)) of single planar heterojunction organic solar cells based on a copper phthalocyanine (CuPc)-buckminsterfullerene (C(60)) active layer. Complete optical and electrical modeling of the cell has been performed taking into account optical interferences and exciton diffusion. Comparison of experimental and simulated external quantum efficiency has allowed us to estimate the exciton diffusion length to be 37 nm for the CuPc and 19 nm for the C(60). The dependence of short-circuit current densities versus the thickness of the PEDOT:PSS layer is analyzed and compared with experimental data. It is found that the variation in short-circuit current densities could be explained by optical interferences.

Interest of broadband optical monitoring for thin-film filter manufacturing

Broadband optical monitoring for thin-film filter manufacturing is more and more developed thanks to better performances of spectrometers with array detectors. We compare this optical monitoring with turning point monitoring and quartz monitoring of different designs. The sensitivity to thickness errors and to refractive index errors is evaluated. We show that real time determination of deposited thickness is a valuable criterion. We also present our experimental setup of transmittance and reflectance broadband optical monitoring. The use of a 400-1000 nm range combined with a signal-to-noise ratio of ~2500 in transmittance and 1000 in reflectance permits us to expect the manufacturing of high-performance non-quarter-wave designs. A first manufacturing of an 18-layer non-quarter-wave high-pass filter is provided.

Index determination of opaque and semitransparent metallic films: application to light absorbers

Index-determination methods based on reflectance and transmittance measurements are developed for both opaque and semitransparent metallic films. Results are given concerning chromium and nickel layers manufactured by electron-beam deposition. To take account of the evolution of the optical constants versus layer thickness, an inhomogeneous layer model is used, which permits us to obtain a good agreement between measurements and calculations. Results are applied to the design and manufacture of light absorbers for which accurate index knowledge is required. Measured absorption is higher than 0.999 on both broadband and monochromatic components.

Manufacturing of an absorbing filter controlled by a broadband optical monitoring

This paper deals with a broadband optical monitoring set up useful for the manufacturing of absorbing coatings. The monitoring strategy consists in simultaneous measurements of transmittance and reflectance over a large spectral range. The resulting analysis allows then to determine the real time deposited thickness. A stage of design correction is possible after the deposition and analysis of each layer. This method has potential for thin metallic layers coatings. We then describe layer after layer the strategy for the control and manufacturing of a filter with given colorimetric properties.

Optical characterization of an unknown single layer: Institut Fresnel contribution to the Optical Interference Coatings 2004 Topical Meeting Measurement Problem

We present the characterizations performed at the Institut Fresnel for the Measurement Problem of the Optical Interference Coatings 2004 Topical Meeting. A single layer coated on a fused-silica substrate of unknown composition and parameters is analyzed in terms of optogeometrical parameters, uniformity, and scattering. We determine the refractive index and the average thickness of the coating, then provide the localized determination of the thickness with a 2 mm spatial resolution. Topography measurements include atomic force microscopy and angle-resolved scattering measurements. These results are completed thanks to a Taylor Hobson noncontact 3D surface profiler.

Ultranarrow bandpass hybrid filter with wide rejection band

The theoretical study and the experimental realization of an ultranarrow bandpass filter, joining a fiber Bragg grating and a dielectric mirror directly deposited at the extremity of the fiber tip, is presented. The features of such a filter are in very good accordance with the results of theoretical simulations.

High-dimensional sensitivity analysis of complex optronic systems by experimental design: applications to the case of the design and the robustness of optical coatings

We present the advantages of experimental design in the sensitivity analysis of optical coatings with a high number of layers by limited numbers of runs of the code. This methodology is effective in studying the uncertainties propagation, and to qualify the interactions between the layers. The results are illustrated by various types of filters and by the influence of two monitoring techniques on filter quality. The sensitivity analysis by experimental design of optical coatings is useful to assess the potential robustness of filters and give clues to study complex optronic systems. OCIS codes: 310.0310, 220.0220, 120.0120. doi: 10.3788/COL201008S1.0021. The study of complex optronic systems entails sensitivity analysis with a large number of parameters. Very often the response depends on synergies or interactions between these parameters. Due to interference characteristics of multilayer filters, optical coatings make possible the evaluation of methods that can explore highdimensional space parameters and the presence of interactions between parts of these parameters. For coatings production with a high number of layers, sensitivity analysis is an efficient way to determine the most critical layers of an optical coating [1] . Refractive index errors or thickness errors during the manufacturing of these layers can induce dramatic consequences on the desired optical properties [2] . We present the advantages of using the method of experimental design [3] , which is used for metamodel constructions and high-dimensional code explorations with limited numbers of runs of the code, particularly in the case of coatings with a high number of layers. This methodology is more effective in studying uncertainties propagation (refractive index or thickness values) to determine the influence of errors on the optical properties, and to quantify the interactions between the errors of each layer. The results are illustrated by various types of filters, particularly bandpass filters and multiple halfwave filters. Different designs such as factorial, fractional factorial, and space-filling designs are used to present the results. Furthermore, we study the influence of two monitoring techniques, and show the most critical coating layers and the dependency of these layers with future manufacturing. The results show that the study of thin-film filters is very useful in examining the interactions of highdimensional systems due to the filter’s adjustable number of layers, and the existence of interactions between these layers. Finally, we demonstrate that sensitivity analysis of optical coatings by experimental design is useful in assessing the potential robustness of filters, and gives clues to study complex optronic systems. The codes to study complex phenomena become more and more realistic with a larger input data set. However, due to the complexity of the mathematical system underlying the computer simulation tools, there are often no explicit input-output formulas. Although computer power has significantly increased in the past years, the evaluation of a particular setting of the design parameters may still be very time-consuming. The simulator is often replaced by a metamodel to approximate the relationship between the code and the design parameters. These metamodels are built using numerical designs of experiments that can indicate interactions between the parameters. The choice of an underlying empirical model (depending on accuracy and interactions level) can be written as Y = Cste + ∑ i biXi + ∑ i

Metal-dielectric light absorbers manufactured by ion plating

In order to improve their mechanic and climatic properties, we studied the manufacturing of metal-dielectric light absorbers using an Ion Plating Process. The choice of the materials, Hf for the metal and SiO2 for the dielectric, allows us of to use the deposition plant for either metal dielectric or all dielectric HfO2-SiO2 coatings without any change. After an index characterization of metallic films, we manufactured monochromatic and broad-band coatings. These coatings have been qualified for space environment.

Light emission from sources located within metallodielectric planar microcavities

A simple, rigorous electromagnetic formula is derived for predicting the electromagnetic power provided by sources located in transparent or dissipative planar microcavities. With this simple approach, we compare numerically and experimentally the electromagnetic power that escapes the microcavity when the source is located in a metallodielectric or in an all-dielectric resonant planar structure. Although a strong light-extraction coefficient might be expected for metallodielectric microcavities, we show that these attractive structures suffer from metal absorption even when thin metallic layers are used. Experiments implemented with europium chelates located in metallodielectric or in all-dielectric microcavities confirm this result.