Wavelength flattened directional couplers for mirrorsymmetric interferometers

In the context of guided optics, we derive, analytically and geometrically, a rigorous general criterion to design wavelength insensitive interferometers with mirror symmetry, which are needed for wavelength multiplexing/demultiplexing. The criterion is applied to a practical case, resulting in an interferometer that works on a band wider than 70 nm.Comment: 21 pages, 9 figure

ESD testing and combdrive snap-in in a MEMS tunable grating under shock and vibration

This work describes a method for tracking the dynamics of electrostatic discharge (ESD) sensitive MEMS structures during ESD events, as well as a model for determining the reduced combdrive snap-in voltage under vibration and shock. We describe our ESD test setup, based on the human body model, and optimized for high impedance devices. A brief description of the MEMS tunable grating, the test structure used here, and its operation is followed by results of the measured complex device dynamics during ESD events. The device fails at a voltage up to four times higher than that required to bring the parts into contact. We then present a model for the snap-in of combfingers under shock and vibration. We combine the results of the analytical model for combdrive snap-in developed here with a shock response model to compute the critical shock acceleration conditions that can result in combdrive snap-in as a function of the operating voltage. We discuss the validity regimes for the combdrive snap-in model and show how restricting the operation voltage below the snap-in voltage is not a sufficient criterion to ensure reliable operation especially in environments with large disturbances

Vibration and shock reliability of MEMS: modeling and experimental validation

A methodology to predict shock and vibration levels that could lead to the failure of MEMS devices is reported as a function of vibration frequency and shock pulse duration. A combined experimental–analytical approach is developed, maintaining the simplicity and insightfulness of analytical methods without compromising on the accuracy characteristic of experimental methods. The minimum frequency-dependent acceleration that will lead to surfaces coming into contact, for vibration or shock inputs, is determined based on measured mode shapes, damping, resonant frequencies, and an analysis of failure modes, thus defining a safe operating region, without requiring shock or vibration testing. This critical acceleration for failure is a strong function of drive voltage, and the safe operating region is predicted for transport (unbiased) and operation (biased condition). The model was experimentally validated for overdamped and underdamped modes of a comb-drive driven SOI-based tunable grating. In-plane and outofplane vibration (up to 65 g) and shock (up to 6000 g) tests were performed for biased and unbiased conditions, and very good agreement was found between predicted and observed critical accelerations

Bragg gratings: Impact of apodization lobes and design of a dispersionless optical filter

Several Bragg-grating (BG) filters employing an asymmetrical and multilobe apodization curve, obtained by inverse-problem solving techniques, have been described in literature. To our knowledge, the roles played by the asymmetry of the apodization function and by each apodization lobe have never been determined. In this paper, the role of the lobes and asymmetry is mathematically analyzed, and the validity of the given description is numerically demonstrated. The physical insight gained allows to optimize the filters obtained as solution of the inverse problem

Composants optiques passifs intégrés pour télécommunications

Cette étude introduit des nouvelles solutions et architectures de dispositif dédiés à des applications dans les systèmes 'Wavelength Division Multiplexing' de communications optiques, à trois niveaux de intégration. La plate-forme du référence est la technologie planaire, standard dans la microélectronique. Au premier niveau d'intégration (à l'échelle de cm) une technique pour la production de réseaux de Bragg en 'Planar Lightwave Circuits' est proposée et vérifiée expérimentalement. A un niveau intermédiaire (à l'échelle de mm) une nouvelle classe de filtres optiques et un 'Tunable Optical Add Drop Multiplexer' basés sur de microanneaux sont étudiés. Au plus haut niveau d'intégration (à l'échelle de la dizaine de microns), la "Self-Collimation" dans les Cristaux Photoniques est exploré. On propose une méthode pour le croisement de guides d'ondes avec la suppression totale de "cross-talk" et le guide d'onde reconfigurable est présenté.This work explores new technological solutions and device architectures for applications in optical Wavelength Division Multiplexing communication systems at three different levels of integration. The technological reference is the planar technology platform, standard in micro-electronics. At the lowest level of integration (order of cm), a technique for producing Bragg Gratings in Planar Lightwave Circuits is proposed and experimentally tested. At an intermediate level of integration (order of mm), a new class of optical filters based on micro-rings is introduced. Exploiting their potentialities, a Tunable Optical Add Drop Multiplexer is introduced and studied. At the highest level of integration (order of tens of mm), Self-Collimation phenomenon in Photonic Crystals is explored. Self-Collimation opens the way to new solutions for old problems (a waveguide crossing with total suppression of crosstalk is proposed) and to new devices (the reconfigurable waveguide is presented).NICE-BU Sciences (060882101) / SudocSudocFranceF

Sub-100 \u3bcs nanoimprint lithography at wafer scale

Display Omitted A full 4\ubf wafer is nanopatterned by an ultrafast thermal NIL process in 100\ub5s.Stamps with integrated heater enable ultrafast cycles at very high temperature.The thermal cycle is implemented with a single short very intense current pulse.A new tool for the ultrafast NIL (or pulsed-NIL) process has been developed.The process applies to a wide range of thermoplastic materials. We present here an ultrafast thermal NIL technology, which enables the patterning of full wafers on the 100\ub5s time-scale. This technique makes use of stamps with a heating layer integrated beneath their nanostructured surfaces. Injecting a single, short (<100\ub5s), intense current pulse into the heating layer causes the surface temperature of the stamp to raise suddenly by hundreds of degrees\ubfC, resulting in the melting of the thermoplastic resist film pressed against it and the swift indentation of the nanostructures. This paper introduces the main aspects of this technology, namely the process concept, the stamp structure, and the main features of the equipment by which the process at the wafer scale was implemented