Philippe Arguel

Direct printing of gratings on sol-gel layers

The sol-gel process is an interesting alternative for making glass integrated-optics components. Reasonable performance can be reached with low-cost fabrication. We show a one-step method for imprinting gratings on a thin layer made through the sol-gel process, thus enlarging the field of application in integrated optics to filters, out-ofplane connections, etc. The efficiency of the grating is studied through diffraction measures and computations.

Experimental characterization of subwavelength diffraction gratings by an inverse-scattering neural method

Characterization of gratings with small period-to-wavelength ratios is difficult to perform but is very helpful in improving the fabrication process. We experimentally tested an inverse-scattering method using a neural network on silicon etched gratings. We also characterized the gratings by using two popular microscopic methods. The validity of each method was determined by comparing measured diffracted intensities with calculated ones obtained from measured profiles. An estimation of accuracy and repeatability was deduced from a scan along a grating sample. This method was thus well validated for nondestructive and noninvasive measurements under experimental conditions that were close conditions of actual usage. This method is easy to implement and requires the measurement of only a few diffracted intensities.

A monolithic optical phase-shift detector on silicon

A novel monolithically integrated device used as an optical phase-shift detector is presented. It consists of a diffraction grating etched at the surface of a p-n photodiode fabricated by a process compatible with a standard silicon CMOS technology. When two coherent light beams are collimated toward the surface of the device, the detected optical power generates a current depending on the relative phase between the two incident beams. The operating principle of this detector and the results obtained by finite-difference time-domain modeling are presented. The fabrication process of the first devices is described and the experimental validation of the concept is demonstrated.

A monolithic phase measurement photodetector

A novel monolithically integrated photodetector used as an optical phase-shift sensor is presented It consists of a diffraction grating etched at the surface of a p-n photodiode fabricated by standard silicon CMOS technology. This device provides the phase relationship between two coherent light beams collimated toward the surface of the photodetector. The operating principle of this sensor is presented along with the first devices fabricated and the experimental validation of the concept is demonstrated by performance characterization.

Effect of Annealing Conditions on Photoluminescence Properties of Low-Pressure Chemical Vapour Deposition-Grown Silicon Nanocrystals

The photoluminescence properties of silicon nanocrystals in SiO2, prepared by low-pressure chemical vapour deposition and subsequent annealing have been studied. A comprehensive range of combinations of film compositions and annealing conditions were tested. The use of two-step annealing (a rapid annealing, followed by a conventional one) used instead of the common one-step conventional annealing, enhances emission. Annealing conditions are key to the photoluminescence and structural properties of the obtained film and have been investigated in detail. Film composition is also an important parameter, which allows tuning of the emission in a wide spectral range in the near infrared.

2 × 1D crossed strongly modulated gratings for polarization independent tunable narrowband transmission filters

We design a narrowband polarization independent transmission guided mode resonance filter whose center wavelength is tunable with respect to the angle of incidence. The device is composed of two identical structures assembled back to back. Each half structure is a dielectric multilayer stack in which a grating is engraved. This so-called 2×1D crossed gratings component has already been demonstrated for reflection filtering [Opt. Lett.36, 1662 (2011)OPLEDP0146-959210.1364/OL.36.001662; Opt. Lett.39, 6038 (2014)OPLEDP0146-959210.1364/OL.39.006038]. The functioning in transmission requires the use of a high index material for the grating bumps. For the design, we resort to a clustering global optimization algorithm, used for the first time to our knowledge for grating structures. We demonstrated two filters with a quality factor of about 4000, tunable over more than 15 nm when the angle of incidence varies over a range of 4°, and with a transmittivity at resonance greater than 95% whatever the incident polarization.

Monolithic diffractive interference detector on silicon

The presented interference detector comprises a standard pn junction in a silicon substrate and a corrugation grating engraved at its surface. Two beams with unknown phase difference impinge onto the detector under the Littrow condition for some diffraction order of the grating. The detected power exhibits a non-zero AC component as the relative phase between the incident beams changes. The present paper describes the operation principle and brings the evidence of non-zero interference contrast in the application case of a displacement sensor.

New optical technology for cold atom experiments

In this proceeding we present a set of studies which are in progress in different labs and industrials. The aim of this project is to study the possibilities to design a very compact and reliable laser cooling bench for space and inboard applications.

Analysis of the sensitivity of a monolithic optical phase-shift detector to geometrical parameter variations

Modelling of a novel monolithic optical phase-shift detector is presented. The device consists of a diffraction grating etched at the surface of a p-n photodiode on silicon. The photodiode generates a current depending on the relative phase between two incident beams collimated toward the diffraction grating. It is shown that the photocurrent contrast, given by the whole range of the phase variation, can be optimised by a precise determination of the period, depth and filling factor of the grating. Detailed analysis of the device performance for TE and TM polarization shows its high sensitivity to the above geometrical parameter variations.

Micromachined tunable optical microfilters design and experimental processing

In this paper we present the design and the experiments performed to obtain a micromechanical voltage tunable Fabry-Perot interferometer integrated with a p-n photodiode on a silicon substrate. It can be used as a voltage tunable filter for the input radiation or as a voltage controlled attenuator to regulate the light from a monochromatic source. Different solution have been analyzed and experimented. The top mirror of the Fabry-Perot cavity is a doped poly-Si or Au/SiO2 movable membrane, electrostatically actuated, obtained using Si micromachining. A complex design process was performed: optical, electomechanical and technological. All these phases were performed interactively. Different materials were considered in order to perform an optimum design. Experimental micromachined interferometers were obtained using two techniques: (1) surface micromachining, and (2) anisotropic etching of (111)-oriented Si wafers, combined with an isotropic pre-etching step. These processes were optimized and matched to the photodiode fabrication process. Monolithic integrated interferometers coupled to p-n photodiodes were obtained.