This paper presents experimental studies on heterodyne Frequency Modulated Continuous Wave (FMCW) signal reception for different optical heterodyne configurations including internal and external mixing between an incoming signal and a local oscillator. Signals and potential noise sources from a fibered FMCW Mach-Zehnder Interferometer (FMCW MZI) are theoretically evaluated. These optical estimations (signal and noise) of various power spectral densities (PSD) are converted into electrical unities to be compared to the measurements.The PSD are validated by using a known alternating voltage with controlled frequency and amplitude. This validation is used to compare the experimental and theoretical detection limits of different FMCW photodetectors, including a Photonic Integrated Circuit (PIC) detector developed and produced at CEA. The detection limit achieved with this PIC module closely matches with the expected theoretical performances. It validates the optical and electronic architecture and the achievements of CEA's design. The miniaturization of this operational detection module is underway. In the future, it will be located on a single chip alongside two Optical Phased Arrays (OPA), one for emission and the other for reception.

This paper presents the thermal behavior of non-resonant (quasi-static) piezoelectric biaxial MEMS scanners with Bragg reflectors. These scanners were developed for LIDAR (LIght Detection And Ranging) applications using a pulsed 1550 nm laser with an average power of 2 W. At this power, a standard metal (gold) reflector can overheat and be damaged. The Bragg reflector developed here has up to 24 times lower absorption than gold, which limits heating of the mirror. However, the use of such a reflector involves a technological process completely different from that used for gold and induces, for example, different final stresses on the mirror. In view of the high requirements for optical power, the behavior of this reflector in the event of an increase in temperature needs to be studied and compared with the results of previous studies using gold reflectors. This paper shows that the Bragg reflector remains functional as the temperature rises and undergoes no detrimental deformation even when heated to 200 °C. In addition, the 2D-projection model revealed a 5% variation in optical angle at temperatures up to 150 °C and stability of 2D scanning during one hour of continuous use at 150 °C. The results of this study demonstrate that a biaxial piezoelectric MEMS scanner equipped with Bragg reflector technology can reach a maximum temperature of 150 °C, which is of the same order of magnitude as can be reached by scanners with gold reflectors.

CEA aims at developing a compact 1550 nm Frequency Modulated Continuous Wave (FMCW) LiDAR on chip. In this paper, individual demonstrators, corresponding to three main components of a LiDAR (Light Distance And Ranging) system, are combined in a test bench: a FMCW laser source, an emission and reception Optical Phased Array (OPA) and an optical heterodyne detection module. Each component has been individually tested, but also evaluated in order to derive the system performance of a complete LiDAR. A test platform has been developed to calibrate an OPA fabricated at CEA platform, either in emission or in reception mode. The tested OPA includes 256 channels based on grating antennae, with 1.5 μm pitch and 256 thermo-optic phase shifters. More recently, this platform has been completed with a FMCW interferometer, where the FMCW LiDAR detection can be evaluated through a mixed propagation setup, composed of optical fibers and free space. Then, the OPA may be inserted into this setup. Therefore, the optical fiber FMCW interferometer has been optimized to detect the lowest signal (typically less than one hundred fW) and to estimate the signal-to-noise ratio (up to almost 30 dB) with low noise photodiodes. Performance has been compared to theoretical predictions. Then, our custom OPA is included inside this experimental setup in a free space propagation environment. The performance measurements extracted from the spectral analysis are in agreement with the expectations.

In order to produce a powerful, single and low divergence output beam for 3D sensing applications, integrated Optical Phased Arrays (OPA) must have a large number of closely spaced optical antennas. This high density leads to specific constraints in component design compared to devices for optical transceivers. Furthermore, OPA characterization requires significant adaptations compared to traditional photonic wafer level measurement systems. In this presentation, we will focus on some key components used in a large scale OPAs, describing specific challenges and solutions. We will show characterization results of single components as well as active beam-steering with OPA circuits using our modified wafer-scale prober setup.

An Optical Phased Array (OPA) is similar to a one dimensional (1D) dynamic diffraction array. The phase law of the emitters is numerically programmable and enables to form a beam, that point towards a targeted direction. OPAs have a high potential for a new generation of LiDAR (Light Detection and Ranging) systems, since they avoid mechanical beam scanning. For the development of such LiDAR, many characterizations are essential to optimize the OPA and to get a full control of their performance. To carry out these tests, CEA-Leti has developed a modular optical bench designed to characterize large scale 1D-OPAs in free space. This bench allows beam-forming calibration at various angles thanks to an optical setup based on far-field imaging in the Fourier plane. This set up directly analyses a field of view of 22° (-11°/+11°) and can rotate in the azimuthal plane of the OPA to cover angles ranging from -50° to +50°. The OPA board is mounted on an additional rotation stage to match the OPA beam output with the beam forming set-up optical axis. For practical use, the optical axis is parallel to the floor (i.e. to the optical table). Moreover, after calibration, additional options allow to switch the setup for practical operations, as the OPA use in real space, e.g. for aiming at a target. A Peltier and a regulation loop allow testing the OPA at various temperatures. Fast photodiodes have been implemented to measure the switching time between distinct angular positions. In this paper, we report data acquired with this setup on a 256 channels OPA operating at @1550 nm, that is based on grating antennas with 1.5 μm pitch and thermo-optic phase shifters.

We report on the characterization of a high channel count Optical Phased Array (OPA) at the wafer level. Using a modified prober, a 256 channel OPA has been successfully calibrated for +/-25° without requiring any packaging steps thus allowing for fast OPA testing.

The struggle against tuberculosis is one of the World Health Organization priorities. Identifying in a short time, patients with active tuberculosis, would bring a tremendous improvement to the current situation. Recovering from this infectious and deadly disease (2 million of death per year) is possible with a correct diagnosis to give an appropriate treatment. Unfortunately, most common tuberculosis diagnoses have few drawbacks:- skin tests: not reliable at 100% and need an incubation of 2 days before the diagnosis,- blood tests: costly and sophisticated technology,- chest X-ray: the first step before the sputum tests used for a bacterial culture with a final diagnosis given within 2 weeks.A tuberculosis test based on exhaled breath analysis is a prospective and noninvasive solution, cheap and easy to use and to transport. This test lies on a fluoregenic detection of niacin, a well-known mycobacterium tuberculosis specific metabolite. In this paper, it is assumed that the selected probe is specific to niacin and that exhaled breath does not contain any interfering species.To address this problem, a fluorimeter is developed with a cheap and cooled CCD (similar to 2k$) as a sensor, to easily determine the suitable "fluorescent zone". In comparing aqueous solutions with and without niacin, 250 pM of niacin have been detected. With a commercial fluorimeter (Fluorolog from Horiba), only 200 nM of niacin are detected. The present detection remains 10 times above the estimated targeted value for a tuberculosis test.The excitation source is a LED, which typically emits 20 mu W at 265 nm through an optical fiber. The emission signal is detected around 545 nm. A typical light exposure lasts 700 seconds.Analysis of biomarkers with a liquid fluorimeter is generic and promising as health diagnosis.

In the framework of a French Joint program COVADIS, an innovative system is developed for the simultaneous detection of benzene, toluene and xylenes in indoor air. The present work is mainly focused on the benzene detection. The detection is based on absorbance measurements over the 250 nm-300nm range with a cooled spectrophotometer. The prototype includes an exposure chamber, which contains five sensors. The sensors are nanoporous disks, whose pore sizes are tailored to efficiently entrap the targeted pollutants. 20 ppb of benzene have been successfully detected within 40minutes of exposure.

A portable device is reported to detect and identify in real time explosive vapors usually used by the terrorists. This device is composed of the multi-sensors chamber with three technologies of explosive vapors sensors: Quartz Crystal Microbalance (QCM), Surface Acoustic Wave (SAW) and fluorescence. The multi-sensors chamber was designed and optimized to guaranty an efficient fluidic repartition on each sensor to assure the suitable responses of sensors. A laptop controls the device. An algorithm has been specifically developed to detect and identify gas nature. On 33 experimentations with various explosives or interferents, the preliminaries results have shown the detection and the identification in about 1min.

A hand-held formaldehyde (HCHO) gas detector has been developed. This fluorescence-based system uses a standard microscope glass slide both as a transducer and a sensor. The selective detection of gaseous formaldehyde is performed using the well-known Hantzsch reaction with Fluoral-P, which is chosen as a reagent. The sensor consists of a nanoporous thin film doped with the reagent, which allows capturing the pollutants molecules. The nanoporous films of polymers are prepared using the Sol-Gel method and are coated on the microscope slide by spin-coating, enabling reproducible coatings of various shapes and thicknesses. Experiments were carried out in the laboratory to calibrate the instrument, with the objective to perform measurements in indoor and outdoor conditions. The real-time monitoring allows detecting pollution peaks of formaldehyde.

Investigations of the sensitivity and selectivity of a capacitive type biosensor array, consisting of a total of 256 biosensing elements, in the detection of single oligonucleotide mutations is presented. The biosensor takes advantage of surface stress changes during biological interactions and is able to translate them into a capacitive signal. The array is organized in a 16×16 matrix of distinct biosensing elements thus allowing for the concurrent sensing of multiple biological targets. In this work the sensing elements of the array are spotted with three different oligonucleotides (CD8, CD17 and CD19) and their hybridization is detected using 36nM PCR. Moreover tests with CD19 revealed the ability of the biosensor to detect the hybridization of the oligo with sample concentrations of 36, 18 and 9nM.

In this paper, defect counting results are presented both on silicon substrates and on EUV mask blanks with their equivalent PSL size distribution. The measurements are achieved with our counting defect prototype COMNET but also with a commercial tool. Improvements of COMNET have been performed to reach sensitivities (PSL equivalent size on silicon) of 80 nm on silicon substrate, 90 nm on EUV mask blank and 125 nm on glass substrate. A first analysis about COMNET repeatability is presented and the impacts of known errors on defect number and size values are evaluated. 2 Typical counting data measured on a EUV mask blank having an added defect density inferior to 1 def/cm(2) (defect size superior to 90 nm) are presented. The analysis of these data shows two main populations of added defects which are characteristic of the deposition process: one close to 100 nm and the other in the micron range. Each group represents half of the total number of added defects. The origins of these defects are finally discussed on the basis of specific experiments chosen to highlight the possible role of the different process steps.

In this study, the nodule growth in ion beam sputtering Mo∕Si coatings used for extreme-ultraviolet (EUV) lithography masks has been studied in relation with the number of Mo∕Si pairs (period 7 nm). To trigger this growth, initial particles of different sizes (d=40–155nm) were used. With a deposition angle of 30° and after the deposition of 40–60 Mo∕Si pairs, the lateral size of nodules was found to grow up to ∼2d while its height ranged from d∕6 to d∕2 depending on the initial particle diameter. This lateral growth was demonstrated to mainly result from shadowing effect. Besides, a vertical smoothing effect was evidenced even in the case of relatively large initial seed particles (70–155 nm). It is attributed to adatom surface diffusion which is also thought to promote a slowdown in the nodule lateral growth when increasing the coating thickness. Finally, a real case of mask blank realization is presented showing that a good knowledge of nodule growth is essential to properly analyze the defect characteristics of EUV mask blanks.

The characteristics of a defect counting tool, COMNET, based on scattering light measurement, is presented. This prototype supports the development of defect-free EUV blanks. Thanks to new improvements, it becomes possible to detect PSL particles having a diameter as low as 100 nm, with a video CCD camera, on silicon substrates or on EUV blanks. To reach this sensitivity, one of the enhancements consists in a laser irradiation close to 65degrees. The present configuration and the use of a CCD camera, with a variable exposure time, should lead to the detection of 80 nm PSL particles deposited on silicon substrate. This extrapolation is based on experimental results and on a simple model.To detect 100 nm particle and smaller particles, it is essential to reduce the level of stray light and to increase the signal to noise ratio. In our application, the stray light essentially comes from three sources : the noise induced by the roughness of the sample, the Rayleigh scattering of the atmosphere, and the stray light in the room. The restrictions induced by these phenomena are described in some detail. All the improvements are not only available for the characterization of silicon substrates but also for transparent blank substrates and for EUV mask blanks. The additional noise induced by the transparent substrate is analyzed. The defects, whatever the component sizes and the component shapes (circular, square,...), can be detected.A cross characterization achieved with a commercial tool on silicon substrate is reported. Counting measurements performed on EUV blanks are shown. Furthermore, a more explicit definition of added defects is proposed.

Our laboratory is involved in the French EUV (Extreme Ultra-Violet) program PREUVE to develop Mo/Si mirrors for blanks free of defects by using an ion beam sputtering deposition technique. This paper illustrates a reduction strategy used to lead to an EUV mirror with a defect density as low as possible. One of the methods adopted is the analysis of the process step by step, therefore, the defect number added by each process step has been quantified. It appears that the most critical step is substrate cleanness. Today, our best performance for a final mirror is 1.2 def/cm2 with a defect size >200 nm. This value has been measured on our home-made counting device COMNET. Our counting device has been validated by comparison with a commercial tool. Two improvements have been implemented on COMNET to increase its routine performance which allows to detect particles of 200 nm. The first one is the sample illumination with a laser in oblique incidence (60°) which increases the signal-to-noise ratio. The noise is the roughness of the sample. The second one is the implementation of a cooled CCD camera with a variable exposure time. Thanks to these improvements, the detection of particles with a diameter size of 155 nm has been demonstrated. On the basis of the experimental results and calculations, the detection of 100 nm particles on silicon and EUV blanks can be reasonably predicted.

As a participant of the French Extreme UltraViolet (EUV) program PREUVE, our laboratory has been involved for one year in the development of Mo/Si blanks free of defects using an Ion Beam Sputtering deposition technique (IBS). Among the different tasks to end at an EUV stepper, the achievement of the blank and its characterization in terms of defect counting is probably one of the most challenging. This is the reason why a characterization tool based on the well known scattering method is under progress in our laboratory. In addition to defect counting, the possibility of cleaning a sample (substrate, blanks....) with a powerful laser source is allowed on the same facility. This set up is fully computerized. Its first performances are illustrated with several examples on our blanks and silicon substrates. Our system is designed to optimize the laser cleaning parameters (wavelength, incidence, polarization....) and to decrease the detection limit size. Today, our facility currently enables the detection of the defect as small as 200 nm in size. Our strategy is to reach the defect size as low as possible and at least until 50 nm, which is the size of interest for the EUV lithography. The major developments under consideration in order to lessen the detection limit size are described in details in this paper.Moreover, the roughness of the EUV blanks may be evaluated with our device. This surface parameter has to be optimized, at least for two reasons : to reduce the optical losses and to decrease the number of defects. The mean to quench the roughness signal in order to detect the smallest defect size and the possibility to evaluate the component roughness are combined on the same facility.The major trumps of our experiment are the visualization of the defects in live, the measurement of the defect sizes and the quick evaluation of the laser cleaning efficiency versus various experimental conditions. The cleaning part of the set up is built up to use various powerful laser sources and to shoot, with the laser, only the locations where the defects remain. Finally, this facility allows to evaluate and to optimize our defect free blank process.

We describe the experimental set-up used to determine the optical densities and the laser damage threshold of laser goggles. Optical densities have been measured at 1064 nm using 3ns laser pulses on an upgraded automatic test bench, which also allows for the determination of laser damage threshold of otpical components. We have performed experiments at constant fluence by varying different parameters such as the angle of incidence, the light polarization, the laser repetition rate, and the spot size. Multiple shot data are obtained in real time, which enables us to detect optical density variations during the laser exposure. From our study, we can conclude that a few goggles show the well known effect of saturable absorbers. This means that, above a given thresholds energy, the goggles become transparent. Finally, we will present a simple model which allows to understand the behavior of the laser damage threshold of polycarbonate goggles under these various conditions.