MEMS devices for the control of trapped atomic particles

This thesis presents the design and characterisation of novel MEMS scanners, for use in systems involving trapped atomic particles. The scanners are manufactured using multiuser silicon-on-insulator MEMS fabrication processes and use resonant piezoelectric actuation based on aluminium nitride thin films to produce one dimensional scanning at high frequencies, with resonance tuning capabilities of up to 5 kHz. Frequencies of ~100kHz and higher are required to enable for example resonant addressing of trapped atomic particles. This work demonstrates how the 200 μm and 400 μm diameter scanners can produce optical deflection angles upwards of 2° at frequencies from 80 kHz to 400 kHz. It proposes an addressing scheme based on Lissajous scanning to steer laser pulses onto 2D grids at a scale compatible with experiments involving single trapped atoms. It also examines frequency tuning capabilities of the scanners using localized on-chip Joule heating and active cooling ; frequency tuning and synchronization are shown to be critical to the implementation of 2-dimensional scanning with multiple scanners. These features are then demonstrated in a prototype implementation using fluorescing samples as a mock target to evaluate the optical performance of the scanning system. Finally, the thesis describes a proof-of-concept for integration of the scanners in a trapped atoms experiment, in which rubidium atoms trapped inside a magneto-optical trap are selectively pumped into a fluorescing state using a beam steered by the MEMS scanners.This thesis presents the design and characterisation of novel MEMS scanners, for use in systems involving trapped atomic particles. The scanners are manufactured using multiuser silicon-on-insulator MEMS fabrication processes and use resonant piezoelectric actuation based on aluminium nitride thin films to produce one dimensional scanning at high frequencies, with resonance tuning capabilities of up to 5 kHz. Frequencies of ~100kHz and higher are required to enable for example resonant addressing of trapped atomic particles. This work demonstrates how the 200 μm and 400 μm diameter scanners can produce optical deflection angles upwards of 2° at frequencies from 80 kHz to 400 kHz. It proposes an addressing scheme based on Lissajous scanning to steer laser pulses onto 2D grids at a scale compatible with experiments involving single trapped atoms. It also examines frequency tuning capabilities of the scanners using localized on-chip Joule heating and active cooling ; frequency tuning and synchronization are shown to be critical to the implementation of 2-dimensional scanning with multiple scanners. These features are then demonstrated in a prototype implementation using fluorescing samples as a mock target to evaluate the optical performance of the scanning system. Finally, the thesis describes a proof-of-concept for integration of the scanners in a trapped atoms experiment, in which rubidium atoms trapped inside a magneto-optical trap are selectively pumped into a fluorescing state using a beam steered by the MEMS scanners

Tiled Polymorphic Temporal Media

International audienceTiled Polymorphic Temporal Media (Tiled PTM) is an algebraic approach to specifying the composition of multimedia values having an inherent temporal quality --- for example sound clips, musical scores, computer animations, and video clips. Mathematically, one can think of a tiled PTM as a tiling in the one dimension of time. A tiled PTM value has two synchronization marks that specify, via an effective notion of tiled product, how the tiled PTMs are positioned in time relative to one another, possibly with overlaps. Together with a pseudo inverse operation, and the related reset and co-reset projection operators, the tiled product is shown to encompass both sequential and parallel products over temporal media. Up to observational equivalence, the resulting algebra of tiled PTM is shown to be an inverse monoid: the pseudo inverse being a semigroup inverse. These and other algebraic properties are explored in detail. In addition, recursively-defined infinite tiles are considered. Ultimately, in order for a tiled PTM to be \emph{renderable}, we must know its beginning, and how to compute its evolving value over time. Though undecidable in the general case, we define decidable special cases that still permit infinite tilings. Finally, we describe an elegant specification, implementation, and proof of key properties in Haskell, whose lazy evaluation is crucial for assuring the soundness of recursive tiles. Illustrative examples, within the Euterpea framework for musical temporal media, are provided throughout

Programmer avec des tuiles musicales: le T-calcul en Euterpea

International audienceEuterpea est un langage de programmation dédié à la création et à la manipulation de contenus media temporisés - son, musique, animations, vidéo, etc... Il est enchassé dans un langage de programmation fonctionnelle avec typage polymorphe: Haskell. Il hérite ainsi de toute la souplesse et la robustesse d'un langage de programmation moderne. Le T-calcul est une proposition abstraite de modélisation temporelle qui, à travers une seule opération de composition: le produit tuilé, permet tout à la fois la composition séquentielle et la composition parallèle de contenus temporisés. En présentant ici une intégration du T-calcul dans le language Euterpea, nous réalisons un outil qui devrait permettre d'évaluer la puissance métaphorique du tuilage temporel combinée avec la puissance programmatique du langage Euterpea

From out-of-time design to in-time production of temporal media

The design a temporal media, a sequence of temporal media values such as notes, sounds, images, etc., is an out-of-time task. Fairly general out-of-time program constructs are available for such a purpose. For example , when writing a musical piece, a composer can traverse back and forth his creation. On the contrary, rendering a temporal media is an in-time task. The production of notes in a musical performance is bound to be coherent with the unceasing onward flow of time. It follows that some of the out-of-time programming constructs used for the creation of that pieces must have been reordered in order to produce the right media events in the right order and at the right time. In this paper, we propose a formal study of the interplay between these in-time and these out-of-time programing constructs. With an explicitly out-of-time design approach, we eventually show that simpler and more abstract declarative programming features become available, leaving to computers the tedious task of synchronizing and scheduling the media events to be produced in-time, upon demand

Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor

The Kv-like K+ channels at the plasma membrane, including the inward-rectifying KAT1 K+ channel of Arabidopsis, are important targets for manipulating K+ homeostasis in plants. Gating modification, especially, has been identified as a promising means by which to engineer plants with improved characteristics in mineral and water use. Understanding plant K+ channel gating poses several challenges, despite many similarities to that of mammalian Kv and Shaker channel models. We have used site-mutagenesis to explore residues that are thought to form two electrostatic counter-charge centers either side of a conserved Phe residue within the S2 and S3 α-helices of the voltage sensor domain (VSD) of Kv channels. Consistent with molecular dynamic simulations of KAT1, we show that the voltage dependence of the channel gate is highly sensitive to manipulations affecting these residues. Mutations of the central Phe residue favored the closed KAT1 channel, whereas mutations affecting the counter-charge centers favored the open channel. Modelling of the macroscopic current kinetics also highlighted a substantial difference between the two sets of mutations. We interpret these findings in context of the effects on hydration of amino-acid residues within the VSD and with an inherent bias of the VSD, when hydrated around a central Phe residue, to the closed state of the channel

On-chip frequency tuning of fast resonant MEMS scanner

The development and characterisation of a piezoelectric actuated high-frequency MEMS scanning mirror with on-chip frequency tuning capability is reported. The resonant scanner operates at frequencies in excess of 140 kHz, generating scan angles of 10 ∘ and 6 ∘ for two orthogonal movement modes with 40 V actuation. On-chip frequency tuning is achieved through electrothermal actuators fabricated adjacent to the mirror main suspension. The electrothermal actuators produce a global and local temperature increase which changes the suspension stiffness and therefore the resonant frequency. A resonance frequency tuning range of up to 5.5 kHz is achieved, with tuning dominant on only one of the two orthogonal scan movement modes. This opens the possibility for precise tuning of a 2D Lissajous scan pattern using a single resonant MEMS scanner with dual orthogonal resonant modes producing full frame update rates up to 20 kHz while retaining the full angular range of both resonant movement modes

Characterization of a fast piezoelectric varifocal MEMS mirror

We present the characterization of a novel design for a varifocal MEMS mirror with piezoelectric actuation and defocus movement up to 100 kHz. The device was simulated using a finite-element method, fabricated using a multi-user silicon-oninsulator process, and its mechanical response to piezoelectric actuation evaluated through laser vibrometry and a dynamic white-light interferometer

Cold-atom shaping with MEMS scanning mirrors

We demonstrate the integration of micro-electro-mechanical-systems (MEMS) scanning mirrors as active elements for the local optical pumping of ultra-cold atoms in a magneto-optical trap. A pair of MEMS mirrors steer a focused resonant beam through a cloud of trapped atoms shelved in the \textit{F}=1 ground-state of \textsuperscript{87}Rb for spatially-selective fluorescence of the atom cloud. Two-dimensional control is demonstrated by forming geometrical patterns along the imaging axis of the cold atom ensemble. Such control of the atomic ensemble with a microfabricated mirror pair could find applications in single atom selection, local optical pumping and arbitrary cloud shaping. This approach has significant potential for miniaturisation and in creating portable control systems for quantum optic experiments.Comment: 4 pages, 3 figure

Fast piezoelectric scanning MEMS mirror for 1D ion adressing

We present a small-scale piezoelectric MEMS micromirror, with resonant frequencies above 300 kHz for 1D scanning. The device is intended for higher frequency operation by reducing the scale of existing designs, and was fabricated using a multi-user silicon-on-insulator process. The performance of the mirror for addressing points along one axis was demonstrated using a free-space optics experimental setup

A high-frequency tunable piezoelectric MEMS scanner for fast addressing applications

We present a high-frequency, tunable, piezoelectric MEMS resonant scanner producing an optical scan angle of more than 2° at frequencies above 100 kHz, with non-contact frequency tuning capabilities. The device is fabricated using a cost-efficient multiuser silicon-on-insulator (SOI) process. The scanner uses thin-film piezoelectric aluminium nitride actuators to drive out-of-plane rotation of a 200 μm diameter mirror plate through mechanical coupling stages. Up to 3.6 kHz frequency tuning is achieved through on-chip thermally actuated non-contact beam tips placed adjacent to the scanner. The scanner is intended for use in small-scale, fast optomechanical applications requiring careful synchronization through frequency tuning