Holes with different sizes from microscale to nanoscale were directly fabricated by focused ion beam (FIB) milling in this paper. Maximum aspect ratio of the fabricated holes can be 5:1 for the hole with large size with pure FIB milling, 10:1 for gas assistant etching, and 1:1 for the hole with size below 100 nm. A phenomenon of volume swell at the boundary of the hole was observed. The reason maybe due to the dose dependence of the effective sputter yield in low intensity Gaussian beam tail regions and redeposition. Different materials were used to investigate variation of the aspect ratio. The results show that for some special material, such as Ni-Be, the corresponding aspect ratio can reach 13.8:1 with Cl₂ assistant etching, but only 0.09:1 for Si(100) with single scan of the FIB. / Singapore-MIT Alliance (SMA)

There is an increasing trend towards miniaturization of micro features as well as micro parts. In order to accurately produce these components and the miniaturized features on them, accurate measurement of the component dimensions is required. However, there are limitations in the dimensional measurement of miniature components: micro-probes and Micro coordinate machines (micro-CMMs) suitable for micro-feature measurement are expensive and fragile so it can be difficult to justify the cost for dimensional verification of batch-produced parts (in many cases miniature components are batch-produced). Therefore, a new cost-effective way for dimensional measurement of miniature components is needed. With this in mind, this thesis describes the development of a novel, three-dimensional measurement system using a rotating wire as a probe and acoustic emissions for contact sensing. This study presents a novel concept of three-dimensional measurements using a rotating wire as a probe and acoustic emission for contact sensing. Experimental results show that the probing system can measure a part with high repeatability. A controller algorithm has been developed for automated scanning within a machine tool. The performance is verified against calibration artifacts. The main contributions of this thesis are as follows: firstly, the traditional contact and non-contact micro coordinate measuring machines including sensing techniques and acoustic emission sensing are reviewed, and a clear set of knowledge gaps are identified in these fields. Secondly, a novel concept of three-dimensional measurements using a rotating wire as a probe tip and acoustic emission for contact sensing is introduced. The operation and measurements of the rotating micro probing based on acoustic emission (AE) sensing are validated experimentally. Initially, the ability of the rotating microprobe tip based on AE sensing to counteract the measured surfaces interaction rubbing is investigated. Other areas of validation are in the determination of the probing point repeatability, the straightness, and probe tip calibration. Thirdly, the acoustic emission signal and its characterizations of the probe tip touches are studied. The behavior of the rotating probe tip focusses on the threshold, touching time and as well as measured materials type that has an effect on probing accuracy. Finally, the estimated effective diameter and approximation threshold are modeled. This work is directly aimed at ensuring that the developed rotating probe tip based on AE sensing is capable of operating in an industrial metrology environment. It is concluded that the developed rotating probe tip based on AE sensing will be able to address the current needs of the micro-CMM community. On the other hand, it is possible that the rotating wire probe tip based on AE sensing can measure micro holes less than the achieved in this work, further increasing its usefulness. / Graduate / elfurjan@uvic.ca

Ce travail de thèse est consacré au développement de sources lasers femtosecondes à haute cadence, de forte puissancemoyenne (>10 W) avec des énergies supérieures à 100 μJ. Ce type de sources est primordial pour le développementd’applications industrielles variées (micro-usinage athermique, chirurgie oculaire, …) ainsi qu’en recherchefondamentale pour l’étude de l’interaction laser matière.Après un chapitre d’introduction sur l’état de l’art des chaînes lasers de forte puissance moyenne à base de matériauxdopés ytterbium, la réalisation d’une chaîne laser de forte puissance moyenne compacte à base de fibre photoniquemicrostructurée à large aire modale sera présentée. Il sera notamment démontré les principales limitations en termed’énergie et de puissance moyenne. D’une part, le fort confinement de l’impulsion lumineuse dans le coeur de la fibrefavorise l’accumulation d’effets non-linéaires lors de l’amplification et détériore la qualité de l’impulsion. D’autrepart, en raison du diamètre de coeur important (> 70 μm) choisit pour lutter contre l’effet précèdent, le guidage dumode fondamental TEM00 de ces fibres est très critique et devient sensible à la charge thermique interne à la fibre.Cette source laser a été utilisée dans le cas de deux applications bien spécifiques : le perçage de plaques d’acierépaisses pour une finalité de déminage (relatif au cadre du financement de cette thèse par la Direction Générale del’Armement) et à la génération d’harmoniques d’ordres élevées à très haute cadence (relatif au domaine d’expertisedu CELIA). Ces deux applications sont traitées au cours du troisième chapitre.A la vue des limitations observées et afin de disposer de chaînes lasers plus énergétiques et offrant des duréesd’impulsions encore plus courtes, une nouvelles architecture d’amplification a été proposée : le pompage fortebrillance de matériaux dopés Ytterbium. Ce concept présenté dans le dernier chapitre utilise le développement desources fibrées monomodes continues émettant à 976 nm. Cette architecture d’amplification a été utilisée afin deréaliser d’une part un oscillateur sub-70 fs et de forte puissance moyenne (>2,3 W) à une cadence de 73 MHz etd’autre part : un amplificateur type « booster » à fort gain. Deux expériences qui ont été réalisées avec des cristauxd’Yb:CaF2. Ce matériaux présente en effet l’avantage d’avoir un très large spectre d’émission (>60 nm) propice à lagénération et amplification d’impulsions femtosecondes mais aussi d’être « compatible » avec les chaînes de trèsforte puissance grâce à sa très bonne conductivité thermique. / This work concerns the development of high repetition rate femtosecond lasers with high average power (>10 W)and energies in excess of 100 μJ. Such lasers are paramount for the development of new industrial applications(athermal micro-drilling, eye surgery, ...) and for fundamental research on high repetition rate laser matter interactionstudies.After a brief introduction and the state of the art summary on high-average power femtosecond laser with ytterbiumdoped materials, a compact high-average power femtosecond laser with a large mode area microstructured rod typeamplifier will be presented. It will browse the main limitations in terms of energy and average power. Limitationsare mainly due to the strong confinement of the electric field propagating in the fibre core leading to non-linear effectsaccumulated during the amplification. On the other hand, for larger core diameter (> 70 μm), the fundamental modeguiding (TEM00) is very weak and thus very sensitive to the internal thermal load of the fibre.This laser source has been used in two specific applications: athermal drilling of thick stainless steel plate for mineclearing(an application of interest for the Direction Générale de l’Armement) and High order Harmonics Generationat high repetition rate (related to CELIA activities). These two applications are presented in the third chapter.In order to stretch the limits and generate more energetic and a shorter pulse, a new amplification scheme has beenproposed, namely high brightness optical pumping of ytterbium doped materials. This concept presented in the lastchapter benefits from the development of high average power single-mode fibre lasers source emitting at 976 nm.This amplification scheme allowed us to realize a high average power Kerr-lens oscillator delivering pulses with apulse duration below than 70 fs and an average power of 2.3W at a repetition rate of 73 MHz. In a second phase, wealso developed a « booster » amplifier with a high single- pass-gain. These two results have been obtained by usingYb-doped CaF2 crystals. This material presents the advantage to have a very broad emission bandwidth (> 60nm)suitable to generate and amplify femtosecond pulses and to be compatible with high average power laser due to hisvery good thermal conductivity.