Bruno Wacogne

Effective piezoelectric activity of zinc oxide films grown by radio‐frequency planar magnetron sputtering

We present a study of the effective piezoelectric activity of thin ZnO films produced by radio‐frequency (rf) planar magnetron sputtering. The energetic plasma particles which bombard the substrate in the above deposition system increase the substrate temperature, thus causing a gradual variation in film structure during the beginning of the film growth. As a result, a precursor layer is formed which consists of small randomly oriented crystallites, exhibiting poor piezoelectric activity. Hence, the film thickness responsible for piezoelectric activity is generally less than the physical thickness of the film and is adjacent to a layer having different acoustic impedance. This leads to an increase in the resonant frequency of the film. For example, a film designed to have a half‐wave resonance at 288 MHz, was found to be resonant at 332 MHz. The poorly structured initial layer meant in this typical case that only 87% of this film volume exhibited piezoelectric activity. Investigations based on the substra...

Simultaneous low coherence interferometry imaging at two depths using an integrated optic modulator

Abstract A Mach–Zehnder unbalanced LiNbO3 integrated modulator with independent control of the phase of each arm is incorporated into the reference arm of a low coherence interferometer set-up. Using different RF modulation frequency and processing electronics tuned to these frequencies, the system can be used for simultaneous interrogation of the signal reflected from two different depths in tissue or from two different axial positions in profilometry. When a pair of XY scanning mirrors are incorporated into the sensing arm, then two en-face images from different axial positions can be simultaneously produced. The depth separation between the axial positions of the points or layers interrogated is equal to half of the modulator path difference. The operation of the system is illustrated by displaying simultaneously two images from a coin.

Gold/Silica biochips: Applications to Surface Plasmon Resonance and fluorescence quenching

We report Gold/Silica biochips for low cost biosensor devices. Firstly, the study of biochemical interactions on silica by means of Surface Plasmon Resonance (SPR) is presented. Secondly, Gold/Silica biochips are employed to reduce the strong quenching that occurs when a fluorophore is close to the gold surface. Furthermore, the control of the Silica-like thickness allows optimizing the distance between the metallic surface and the fluorophore in order to enhance the fluorescent signal. These results represent the first steps towards highly sensitive, specific and low cost biosensors based, for example, on Surface Plasmon Coupled Emission (SPCE) techniques.

Security vulnerability in coherence modulation communication systems

A simple method for detecting a signal encoded by coherence modulation without the use of any decoder interferometer is demonstrated. The technique is based on wavelength filtering of the channelled spectrum in the transmission link. To overcome this vulnerability in the scheme, more secure coherence modulation arrangements are proposed.

Single lithium niobate crystal for mode selection and phase modulation in a tunable extended-cavity laser diode

A 1540-nm external-cavity laser diode with an intracavity electro-optic wavelength tuner is demonstrated. Coarse- and fine-wavelength tuning is achieved with a single lithium niobate wavelength tuner. One section of the crystal is used as a tunable-wavelength filter to tune the wavelength by mode hopping. The other operates as a phase modulator to change the optical length of the cavity and to tune the wavelength continuously. Coarse tuning by mode hopping is obtained over a range of 5.3 nm with a tuning rate of 580 MHz/V. Continuous tuning is obtained over 82% of the free spectral range of the cavity. The wavelength switching time is 10 ns for the cavity used.

Gold/silica thin film for biosensors applications: Metal enhanced fluorescence

The work described here concerns the fabrication of cost-effective biosensors that permit to amplify a fluorescence signal without a complex nano-structuration of the surface. The idea is to put to profit the natural pseudo nano-structuring that is observed when depositing metallic layers by various micro-fabrication techniques. This new architecture consists of a glass substrate. A gold film is deposited on the top of it and a silica layer onto the gold. A dye (Cy5) is then absorbed onto the surface and the fluorescence intensity is measured. This intensity depends on the distance between the dye and the metal. It also depends on the properties of the metallic film. The goal of the work is to determine which gold deposition method leads to the highest fluorescence amplification and which silica thickness is required to achieve this amplification.

Enhanced security in a coherence modulation system using optical path difference corruption

The security aspect of coherence modulation for telecommunication is discussed. We have recently demonstrated a simple technique for decoding the signal without any decoder interferometer. A secure alternative method based on the corruption of the interferometers optical path difference is now shown.

Microsensors and image processing for single oocyte qualification: toward multiparametric determination of the best time for fertilization

During intracytoplasmic sperm injection (ICSI) attempts, oocytes reaching metaphase II are microinjected. A morphological examination under a microscope is the usual method for determining oocyte maturity. The level of oocyte maturity is based on the meiotic status (Germinal Vesicle, metaphase I and metaphase II) of the oocytes with respect to their increasing maturity. In this letter, we summarize the studies conducted to analyze cytoplasm maturity using various microsystems and image processing. Optical microsystems are used to measure the transmission spectra and refractive index of the oocytes. We compared the transmission spectra measurements to the transmission electron microscopy results. Karhunen–Loeve transform is also used to evaluate the maturity of the oocytes. To summarize, optical analysis techniques are a minimally invasive technology allowing cytoplasm maturity to be assessed. Oocytes should not only be qualified in terms of GV, MI or MII, but also regarding their temporal evolution over the course of these maturation stages. The ultimate aim of this work is to describe the maturation of the oocytes by a trajectory in a multidimensional space and to determine when would be the best time for successful fertilization.

Double security level in a telecommunication system based on phase coding and false data transmission

A new communication system exhibiting a double security level is demonstrated. Information coding is based on relative phase changes between consecutive time intervals of the light emitted from a highly coherent CW source. An imbalanced Mach-Zehnder interferometer whose time delay matches the intervals duration is used to decode the data. The first security level is related to the constant optical power in the transmission link. To further enhance the security, a low coherent source is used to send false data down the transmission link. Common mode rejection is used to separate the real signal from the false signal. This system provides a high signal-to-noise ratio as well as a low crosstalk in a wavelength division multiplexing network.

Modeling of C-SNARF-1 pH Fluorescence Properties: Towards Calibration Free Optical Fiber pH Sensing for in Vivo Applications

Organic functions of the human body are related to biological constants. Variations of these constants, among them pH, induce pathological troubles. The general goal of our work is to fabricate a fluorescent pH sensor at the end of an optical fiber for in vivo pH measurements. One difficulty using fluorescence indicators is the need to perform an accurate calibration. In this communication, we present methods used to simplify and potentially avoid calibration procedures of fluorescence indicators. The first method concerns the simplification of calibration procedures making them independent of the indicator’s concentration, path length and equipment used. The second method concerns modelling the fluorescence emission of the molecules as a function of pH only. This model is used to fit the exact shape of C-SNARF-1 fluorescence spectra obtained at any pH. Subsequently, the pH of a solution can be computed with an accuracy of 0.1 pH unit without the calibration procedure employed up to now. These methods constitute the first steps toward calibration free pH measurements. They can be applied to any fluorescent indicator exhibiting a dual emission peak. As a conclusion, this is the first time that fluorescence properties of C-SNARF-1 are fully mathematically