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This paper presents infrared photonic multiplexers integrated on silicon designed to be assembled with QCL or ICL arrays in order to realize different possible broadband powerful tunable sources in the mid-infrared for multi-gas sensing.

It is demonstrated that the use of X-ray specular reflectivity (XRSR) to measure the geometrical thickness of thin layers allows one to overcome the thickness-optical property correlation in ellipsometry. In addition, a quasi-achromatic compensator is fitted to a rotating polarizer ellipsometer allowing the measurement of cos Δ with an accuracy better than 10 −4 for values close to one, over the entire 0.25–1.7-μm spectral range. This set up is applied to the study of transparent materials such as Ion Beam Sputtering (IBS) of thin SiO 2 layers deposited on silica glass substrates. Thus, a transition layer at the top surface of the substrate has been detected through the cos Δ measurements. Ellipsometric results are in very good agreement with those obtained by photogoniometry. The knowledge of the optical properties of IBS SiO 2 leads to a complete understanding of the ellipsometric response of a TiO 2 /SiO 2 mirror.

CEA-LETI and CNES have successfully realized a helium-4 isotropic space-qualified magnetometer for the SWARM mission. The present paper reviews the progress made in the miniaturization of this isotropic optically pumped magnetometer. Sensor isotropy is provided by a liquid crystal polarization rotator that sets the pumping beam polarization at 90° with respect to the ambient magnetic field. It allows a continuous polarization rotation from 0° to more than 300° with response times sufficient for mobile or space applications. This rotator is non-magnetic and can be easily integrated close to the gas cell. The miniature sensor reaches a sensitivity of 10 pT/√Hz in a bandwidth from DC to 100 Hz.

In current research on optical phase change data storage, it is essential to understand accurately the physics underlying writing and erasing processes. Computer simulation combined with the appropriate physical models and experimental data is the most valuable tool available. We have established optical, thermal and phase transformation (thermodynamics and kinetics) models and constructed a simulation based on them. We use this simulation to reproduce and forecast the writing and erasing processes of GeSbTe and GeSbTeSn with GeN interlayers in the case of dual level DVR (digital video recording) discs.

Knowledge and control of a technological process require efficient tools to have a good insight during and after deposit. In situ controls have many advantages because they provide a real time insight on the changes which occur in the deposit with a certain accuracy. However, the in situ measurement does not enable real time feedback on the technological parameters. We therefore developed techniques to characterize samples after deposition. We will show in this paper that the complementarity between optical and X-ray techniques can lead to very fine results. Our deposition chamber is provided with an original system which enables a sampling of some monolayers from the stack. The Investigation of these monolayers help to make a reverse engineering on stacks of several layers.

In the field of imaging optical systems, anti-reflective (AR) coatings are widely used in order to reduce unwanted reflections. The LETI-CMO laboratory is involved in the development of an advanced spectral separator for earth observation [1] which uses absorbing diaphragms for the separation of the different optical paths. The optical specifications of such a sytem are drastic since a reflection lower than 2% and a transmission lower than 10-3 are required on a spectral range as wide as 450 to 950 nm. In order to meet such specifications, we have chosen to develop an absorbing AR coating based on a new multilayer structure which uses thin metallic absorbing layers. As we will see, such structures exhibit particularly efficient absorbing properties.

An apparatus for immersion interferometric lithography is described here where the interfering beams are created by illuminating a first diffraction grating followed by a second diffraction grating recombining the diffracted beams onto the photoresist plane. The main advantage of this system is to be achromatic: thus it is possible to use a basic commercial ArF excimer laser as the exposure source. We present here the calculations made to evaluate the different parameters that can influence the depth of focus in the immersion configuration. As the setup is mainly based on the two diffraction gratings, it matters to properly design it. The purpose of this article is to show the optimization made on the diffraction gratings in taking into account their fabrication process since they are fabricated using the capabilities of the silicon line available in our laboratory. On one hand, calculations have been done to determine the second grating period as a function of the first grating period and the “immersion ...

Downsizing and compatibility with MEMS silicon foundries is an attractive path towards a large diffusion of photoacoustic trace gas sensors. As the photoacoustic signal scales inversely with the chamber volume, a trend to miniaturization has been followed by several teams. We review in this article the approach initiated several years ago in our laboratory. Three generations of components, namely a 40 mm3 3D-printed cell, a 3.7 mm3 silicon cell, and a 2.3 mm3 silicon cell with a built-in piezoresistive pressure sensor, have been designed. The models used take into account the viscous and thermal losses, which cannot be neglected for such small-sized resonators. The components have been fabricated either by additive manufacturing or microfabrication and characterized. Based on a compilation of experimental data, a similar sub-ppm limit of detection is demonstrated. All three versions of photoacoustic cells have their own domain of operation as each one has benefits and drawbacks, regarding fabrication, implementation, and ease of use.