The fabrication of optical filters whose reflection/transmission response is spatially-graded has been the object of numerous research studies over the past decades given their applications in areas including multi- and hyperspectral imaging, structural colouring and even holographic encryption. In this context, the key enabling feature is the ability to tailor the thickness profile of at least one layer of the optical coating multilayer stack. To-date, this 3-dimensional structuration has been achieved either at the deposition stage or as an additional post-deposition process step. In the former case, the technique relies on the shaping of the material deposition flux thanks to the insertion of a (moving) mask inside the evaporation or sputtering machine. As such, the method is usually limited to the implementation of centimetre-scale variations. A contrario, to reach sub-millimeter-scale features, the preferred approach is based on postdeposition layer structuration, which is performed using grayscale lithography in the form of multi-(mask-)level optical lithography, or using e-beam or laser lithography. All these approaches are nevertheless relatively complex since they involve either multiple steps or need a very precise calibration of the exposition curve. In this paper, we report that the evaporation through re-usable shadow masks can be used to create optical filters whose spatial variations can be controlled with a ~70-µm-resolution. Using metal-mirror Fabry-Pérot interferometer structures as representative optical filters, we demonstrate the ability to adjust the resonance wavelength, the filter bandwidth and extinction ratio, and the coupling strength and splitting in cascaded resonators.
Based on the micro-electronics fabrication process, Micro-Opto-Electro-Mechanical Systems (MOEMS) are under study in order to be integrated in next-generation astronomical instruments for ground-based and space telescopes. Their main advantages are their compactness, scalability, specific task customization using elementary building blocks, and remote control. At Laboratoire d’Astrophysique de Marseille, we are engaged since several years in the design, realization and characterization of programmable slit masks for multi-object spectroscopy and micro-deformable mirrors for wavefront correction. First prototypes have been developed and show results matching with the requirements.
This paper describes the development of a new technological process for manufacturing MEMS with out-of-plane
motion in order to develop voltage references with high stability (deviation from the nominal value less than some 10-6per year) and working in alternating current (AC). In this application, the AC voltage reference is defined at the pull-in
point of the MEMS variable capacitor made of two electrodes, one fixed and the other movable driven by an AC current
having a frequency much higher than the mechanical resonant frequency. This process has been developed to get MEMS
devices exhibiting high nominal capacitances, which makes the development of the read-out electronics easier, and
metallized electrodes to avoid charge effects on the stability of the voltage standard. Moreover, this process allows to
realize stoppers, in order to get a good operational reliability.
In this paper we describe the use of thermo-activated PNIPAM nano-material in optical switching devices. In other publications, the PNIPAM is used either as a carrier for crystalline colloidal array self-assemblies or as micro-particles that serve as pigment bags. In this publication we use a simpler-to-fabricate pure PNIPAM solution in a semi-dilute regime. The PNIPAM devices produced are transparent at temperatures below a critical temperature of 32°C and become diffusing above this temperature. We show that at 632nm the transmission through the devices is about 75% in the transparent state while the additional attenuation achieved in the diffusing state is of the order of 38 dB. The experimental fall and rise times obtained are large (about 300ms and 5s respectively) due to the non-optimised thermal addressing scheme. In addition, spectral measurements taken in the infrared spectrum (700-1000nm) demonstrate that the cell response is flat over a large portion of the infrared spectrum in both the transparent and the diffusing states.
Future adaptive optics (AO) systems require deformable mirrors with very challenging parameters, up to 250 000
actuators and inter-actuator spacing around 500 &mgr;m. MOEMS-based devices are promising for the development of a
complete generation of new deformable mirrors. Our micro-deformable mirror (MDM) is based on an array of
electrostatic actuators with attachments to a continuous mirror on top. The originality of our approach lies in the
elaboration of layers made of polymer materials. Mirror layers and active actuators have been demonstrated. Based on
the design of this actuator and our polymer process, realization of a complete polymer-MDM has been done using two
process flows: the first involves exclusively polymer materials while the second uses SU8 polymer for structural layers
and SiO2 and sol-gel for sacrificial layers. The latest shows a better capability in order to produce completely released
structures.
The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then,
we have developed a dedicated 14-bit electronics in order to "linearize" the actuation, using a calibration and a sixth-order
polynomial fitting strategy. The response is nearly perfect over our 3×3 MDM prototype with a standard deviation
of 3.5 nm; the influence function of the central actuator has been measured. First evaluation on the cross non-linarities
has also been studied on OKO mirror and a simple look-up table is sufficient for determining the location of each
actuator whatever the locations of the neighbor actuators.
Electrostatic MDM are particularly well suited for open-loop AO applications.
Next generation adaptive optical (AO) systems require deformable mirrors with very challenging parameters, up to
250 000 actuators and inter-actuator spacing around 500μm. MOEMS-based devices are promising for the development
of a complete generation of new deformable mirrors. We are currently developing a micro-deformable mirror (MDM)
based on an array of electrostatic actuators with attachments to a continuous mirror on top. The originality of our
approach lies in the elaboration of layers made of polymer materials. Mirrors with very efficient planarization and
active actuators have been demonstrated, with a piston motion of 2μm for 30V. Using our dedicated characterization
bench, we have measured a 6.5kHz resonance frequency, well suited for AO applications. Based on the design of this
actuator and our polymer process, realization of a complete polymer-MDM is under way.
The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then,
we have developed a dedicated 14-bit electronics in order to "linearize" the actuation. After calibrating the behavior of
each actuator and fitting the curve by a sixth order polynomial, the electronics delivers a linearized output. The response
is nearly perfect over our 3×3 MDM prototype with a standard deviation of 3.5 nm, and we have then obtained the
influence function of the central actuator. First evaluation on the cross non-linarities has also been evaluated on the
OKO mirror and a simple look-up table is sufficient for determining the location of each actuator whatever the locations
of the neighbor actuators. Electrostatic MDM are particularly well suited for AO applications.
Highly performing adaptive optical (AO) systems are mandatory for next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes, for studying new fields like circumstellar disks and extra-solar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. We are currently developing a micro-deformable mirror (MDM) based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. In order to reach large stroke for low driving voltage, the originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. We have developed the first polymer piston-motion actuator: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V, and measured resonance frequency of 6.5kHz is well suited for AO systems. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. We have successfully developed a dedicated 14-bit electronics in order to "linearize" the actuation. Actual location of the actuator versus expected location of the actuator is obtained with a standard deviation of 21 nm. Comparison with FEM models shows very good agreement, and design of a complete polymer-based MDM has been done.
Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems, for studying new fields like circumstellar disks and extrasolar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. However, only limited strokes for large driving voltages have been demonstrated. In order to overcome these limitations, we are currently developing a micro-deformable mirror based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials, using low-temperature process. This process allows the realization of high optical quality mirrors on top of an actuator array made with various techniques. We have developed the first polymer piston-motion actuator in order to reach high strokes for low driving voltages: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V. Preliminary comparison with FEM models show very good agreement and design of a complete polymer-based MDM looks possible.
Electrostatic micromirrors are yet a well-known topic in the world of MOEMS. But in some specific cases, the mirror dimensions should have to be extended in order to be able to switch beams of a larger diameter. In other words, the convergence in dimensions between electronic technologies and classical machining in the range of hundreds microns to millimetre was not yet explored. This is the context of our study, whose goal is to make digital switching devices with a size of some millimetres and a large, pre-fixed deflection angle of ten degrees.
KEYWORDS: Microelectromechanical systems, Reliability, Commercial off the shelf technology, Finite element methods, 3D modeling, Physics, Failure analysis, Profilometers, Capacitance, Material characterization
COTS (Commercial-off-the-shelf) MEMS components are very interesting for space applications because they are lightweight, small, economic in energy, cheap and available in short delays. The reliability of MEMS COTS that are used out of their intended domain of operation (such as a space application) might be assured by a reliability methodology derived from the Physics of Failure approach. In order to use this approach it is necessary to create models of MEMS components that take into consideration environmental stresses and thus can be used for lifetime prediction. Unfortunately, today MEMS failure mechanisms are not well understood today and therefore a preliminary work is necessary to determine influent factors and physical phenomena. The model development is based on a good knowledge of the process parameters (Young’s modulus, stress...), environmental tests and appropriated modeling approaches, such a finite element analysis (FEA) and behavioural modeling. In order to do the environmental tests and to analyse MEMS behaviour, we have developed the Environmental MEMS Analyzer EMA 3D. The described methodology has been applied to a Commercial-off-the-shelf (COTS) accelerometer, the ADXL150. A first level behavioral model was created and then refined in the following steps by the enrichment with experimental results and finite element simulations.
Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems. Different types of AO systems are currently under study, including Multi-Conjugate AO (MCAO), high dynamic range AO, and low-order AO for distributed partial correction AO. These systems require a large variety of deformable mirrors with very challenging parameters. The development of new technologies based on micro-opto-electro-mechanical systems (MOEMS) is promising for future deformable mirrors. The major advantages of the micro-deformable mirrors (MDM) are their compactness, scalability, and specific task customization using elementary building blocks. We are currently developing a MDM based on an array of electrostatic actuators with attachments to a continuous mirror on top. A high optical quality mirror is the most challenging building block for this device. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. With this structure, very efficient planarization has been obtained: the long-distance flatness is below 0.2 μm, the print-through of localized 9μm steps is reduced to below 0.5μm and a rms roughness of 15 nm has been measured over the surface. The integration of this mirror surface on top of an actuator array is under investigation.
The objective of the MICROMED CNRS project is the design of a complete microsystem usable in the treatment in vivo of hypertensives. The microsystem which corresponds with this objective includes different elements such as pressure sensors, a drug reservoir, a monitoring chip and a drug delivery system that necessitates the use of a dosing micropump able to deliver daily does of few microliters in several shots. We will focus here on the micropump:microfabrication technology, assembly and test. The fact that the fluid actuating membrane, the input and output fluid gates, and the two passive microvalues are together on a single silicon chip of 1 cm3 area makes this pump original. The fabrication technology combines the techniques of microelectronics and MEMS: micromachining for the square membrane and the fluid gates, sacrificial oxide layers and LPCVD polysilicon deposition for the microvalves. The assembly of the different parts is based on existing techniques like anodic bonding, gluing with adhesive films...we have investigated the fabrication of the micro pump with an electrostatic actuation. Tests are in progress for the first prototypes on a specific experimentation set- up in order to: (i) study the flowing of different fluids into the pump, (ii) study the directionality of the valves by plotting the flow rate/pressure (Phi) (P) diagram, (iii) study the pump functionality.
The chemical analysis plays an important role in a clinical medicine. A small size of the analyzing system and reduced sample volume are required. Fully recognizing the benefits of this technology, we are working in the frame of a European project called BARMINT (basic research for microsystem integration) and is concerned with the development of a novel microsystem containing chemical and pressure sensors for the chemical analysis of fluids.
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