No description available.

Malignant or benign tumors may be ablated with high‐intensity focused ultrasound (HIFU). This technique, known as focused ultrasound surgery (FUS), has been actively investigated for decades, but slow to be implemented and difficult to control due to lack of real‐time feedback during ablation. Two methods of imaging and monitoring HIFU lesions during formation were implemented simultaneously, in order to investigate the efficacy of each and to increase confidence in the detection of the lesion. The first, Acousto‐Optic Imaging (AOI) detects the increasing optical absorption and scattering in the lesion. The intensity of a diffuse optical field in illuminated tissue is mapped at the spatial resolution of an ultrasound focal spot, using the acousto‐optic effect. The second, Harmonic Motion Imaging (HMI), detects the changing stiffness in the lesion. The HIFU beam is modulated to force oscillatory motion in the tissue, and the amplitude of this motion, measured by ultrasound pulse‐echo techniques, is influenced by the stiffness. Experiments were performed on store‐bought chicken breast and freshly slaughtered bovine liver. The AOI results correlated with the onset and relative size of forming lesions much better than prior knowledge of the HIFU power and duration. For HMI, a significant artifact was discovered due to acoustic nonlinearity. The artifact was mitigated by adjusting the phase of the HIFU and imaging pulses. A more detailed model of the HMI process than previously published was made using finite element analysis. The model showed that the amplitude of harmonic motion was primarily affected by increases in acoustic attenuation and stiffness as the lesion formed and the interaction of these effects was complex and often counteracted each other. Further biological variability in tissue properties meant that changes in motion were masked by sample‐to‐sample variation. The HMI experiments predicted lesion formation in only about a quarter of the lesions made. In simultaneous AOI/HMI experiments it appeared that AOI was a more robust method for lesion detection. / Bernard M. Gordon Center for Subsurface and Imaging Systems (CenSSIS) via the NSF ERC award number EEC‐9986821.

Acousto-optic (AO) sensing and imaging (AOI) is a dual-wave modality that combines ultrasound with diffusive light to measure and/or image the optical properties of optically diffusive media, including biological tissues such as breast and brain. The light passing through a focused ultrasound beam undergoes a phase modulation at the ultrasound frequency that is detected using an adaptive interferometer scheme employing a GaAs photorefractive crystal (PRC). The PRC-based AO system operating at 1064 nm is described, along with the underlying theory, validating experiments, characterization, and optimization of this sensing and imaging apparatus. The spatial resolution of AO sensing, which is determined by spatial dimensions of the ultrasound beam or pulse, can be sub-millimeter for megahertz-frequency sound waves.A modified approach for quantifying the optical properties of diffuse media with AO sensing employs the ratio of AO signals generated at two different ultrasound focal pressures. The resulting “pressure contrast signal” (PCS), once calibrated for a particular set of pressure pulses, yields a direct measure of the spatially averaged optical transport attenuation coefficient within the interaction volume between light and sound. This is a significant improvement over current AO sensing methods since it produces a quantitative measure of the optical properties of optically diffuse media without a priori knowledge of the background illumination. It can also be used to generate images based on spatial variations in both optical scattering and absorption. Finally, the AO sensing system is modified to monitor the irreversible optical changes associated with the tissue heating from high intensity focused ultrasound (HIFU) therapy, providing a powerful method for noninvasively sensing the onset and growth of thermal lesions in soft tissues. A single HIFU transducer is used to simultaneously generate tissue damage and pump the AO interaction. Experimental results performed in excised chicken breast demonstrate that AO sensing can identify the onset and growth of lesion formation in real time and, when used as feedback to guide exposure parameters, results in more predictable lesion formation. / Bernard M. Gordon Center for Subsurface and Imaging Systems (CenSSIS) via the NSF ERC award number EEC-9986821.

Mise en oeuvre de circuits intégrés dédiés à l’analyse des corrélations temporelles des tavelures optiquesOn pourrait chercher à exploiter, à des fins de diagnostic médical, la forte pénétration au sein des tissus biologiques de la lumière située dans l’infrarouge proche. Cependant la nature diffusante des tissus brouille fortement l’information spatiale, et il faut mesurer plusieurs paramètres pour obtenir des informations pertinentes, avec par exemple des mesures résolues en temps, ou des mesures de corrélations de speckle. Ces dernières sont délicates de par le faible flux lumineux dans un grain de speckle et les temps de corrélations très courts observés avec les tissus. L’équipe d’optique en milieu aléatoire du Laboratoire de Physique des Lasers a développé, en collaboration avec l’Institut d’Electronique Fondamentale, un concept de circuit multipixels dédié à la détection et à l’analyse du speckle. Ce circuit traite individuellement différents grains de speckle en parallèle, et calcule en temps réel une grandeur moyenne sur l’ensemble des pixels, améliorant ainsi le rapport signal à bruit. Chaque pixel de détection est capable d’effectuer une détection synchrone du signal, et de calculer différentes corrélations temporelles. L’objectif de cette thèse était de caractériser une nouvelle génération de circuits, et de les mettre en oeuvre dans différentes expériences d’optique diffuse. Nous avons pu, au cours de ces travaux, mesurer les corrélations temporelles du speckle en fonction du temps de transit à travers 4cm de lait, et ce malgré la décorrélation très rapide observée dans ce cas. Nous avons également réalisé des expériences d’imagerie acousto-optique, en collaboration avec l’Institut Langevin, en développant un nouveau protocole de mesure adapté à notre technologie. / Implementation of Application Specific Integrated Circuits dedicated to the analysis of speckle patterns temporal correlationsThe fact that near infrared light has a good penetration depth inside biological tissues calls to its exploitation for medical diagnosis purposes. However, given their scattering nature, tissues strongly blur the spatial information. One therefore needs to measure several parameters in order to obtain pertinent information. One can for instance use time-resolved detection, or measure speckle correlations. The latter implies serious technological bottlenecks due to the weakness of the light flux in one speckle grain, and due to the very short correlation times observed in tissues. The biomedical optics group of Laboratoire de Physique de Lasers, in collaboration with Institut d'Electronique Fondamentale, has developed a concept of multipixels ASIC dedicated to speckle detection and analysis. This device processes different speckle grains in parallel, and computes an averaged value across all the pixels in real time in order to improve the signal to noise ratio. Each detection pixel can perform a lock-in detection of the signal, and compute different time correlations. The objective of this thesis is to characterize a new generation of circuits, and to implement them in different experiments on diffuse light propagation. One highlight of this work is the fact that we could compute speckle time correlation as a function of the transit time through 4 cm of milk, despite the very fast decorrelation obtained with such a medium. In addition, we performed acousto-optic imaging experiments with our partners from Institut Langevin, developing for that purpose a new protocol appropriate to our technology.

Desde o desenvolvimento dos primeiros métodos de controle do movimento e posição de partículas usando lasers, ainda no início da década de 1970, até o reconhecimento com o prêmio Nobel de Física de 2018, uma das principais e mais versáteis ferramentas de manipulação óptica, as chamadas pinças ópticas, têm sido usadas majoritariamente para explorar objetos em dois regimes de tamanho: o limite das partículas sub-nanométricas (átomos e moléculas simples) e o limite das partículas micrométricas (com aplicações especialmente em sistemas biológicos). Nesse trabalho, foi desenvolvido e construído um aparato experimental para aprisionar micro e nanopartículas numa pinça óptica, que pode ser controlada de forma dinâmica usando modulação acusto-óptica do feixe de aprisionamento. A calibração da pinça óptica foi feita por diversos métodos, incluindo o método de equipartição de energia e análise do potencial óptico, resultando em forças de aprisionamento da ordem de piconewtons por micrometros. Ademais, simulações computacionais de modelos estocásticos foram realizadas com o intuito de comparar os resultados experimentais com àqueles previstos teoricamente e guiar estudos futuros. / Since the development of early methods for controlling the motion and position of particles using lasers, in the 1970s, to the recognition with the 2018 Nobel Prize for Physics, one of the most versatile optical manipulation tools, the so-called optical tweezers, have been used mostly to explore objects in two limits of sizes: the sub nanometric particles (atoms and simple molecules) and the micrometric particles (with applications especially in biological systems). In this work, an experimental apparatus was developed and built to trap micro and nanoparticles in an optical tweezer that can be dynamically controlled, using acoustic-optical modulation of the trapping beam. The calibration of the optical tweezer was done using several methods, including the energy equipartition method and optical potential analysis, resulting in trapping forces on the order of piconewtons per micrometers. In addition, computational simulations of stochastic models were performed with the purpose of comparing the experimental results with those predicted theoretically and guiding future studies.

Experimental and theoretical progress has been made toward the production and manipulation of novel atomic and molecular states. The design, construction and characterization of a driver for an acousto-optic modulator is presented which achieves a maximum diffraction efficiency of 54 % at 200 MHz, using a commercial modulator. A novel design is presented for a highly sensitive optical spectrum analyzer for displaying laser mode structure in real time. Utilizing programmable microcontrollers to read data from a CMOS image sensor illuminated by the diffraction pattern from a Fabry-Perot interferometer, this device can operate with beam powers as low as 3.3 micro-watts, at a fraction of the cost of equivalent products. Computational results are presented analyzing the behaviour of a model quantum system in the vicinity of an avoided crossing. The results are compared with calculations based on the Landau-Zener formula, with discussion of its limitations. Further computational work is focused on simulating expected conditions in the implementation of the STIRAP technique for coherent control of atoms and molecules in the beam experiment. The work presented provides tools to further the aim of producing large, mono-energetic populations of heavy Rydberg systems. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-10-03 17:17:56.841

Akustinių bangų ir šviesos – akustooptinė (AO) sąveika įgalina tirti akustinių bangų savybes ne tik kristalo paviršiuje, bet ir tūryje. Tai aktualu kuriant tūrinių bangų prietaisus įvairiems taikymams. Iki šiol yra atlikta keletas AO difrakcijos eksperimentų, kai sunertiniais keitikliais žadinamos tūrinės bangos, bet ne nuotėkio paviršinių akustinių bangų (PAB) spinduliuotė į tūrį. Kita vertus, AO sąveiką galima efektyviai panaudoti šviesos parametrų valdyme. Tūrinių bangų AO prietaisai – šviesos moduliatoriai, deflektoriai, derinami filtrai plačiai naudojami praktikoje. Šioje disertacijoje pateikiami anizotropinės šviesos difrakcijos nuotėkio paviršinių akustinių bangų spinduliuote į kristalo tūrį ZX-LiNbO3 ir YX-LiTaO3 eksperimentiniai rezultatai ir teorinis modelis. Tokio tipo sąveika įgalina suderinti sunertinių PAB keitiklių technologijos privalumus su didesniu šviesos sąveikos su tūrinėmis akustinėmis bangomis efektyvumu. Dėmesys mišraus valentingumo manganitams, turintiems perovskito kristalinę gardelę vis didėja dėl fazinio virsmo paramagnetikas – feromagnetikas Kiuri temperatūroje, milžiniškosios magnetovaržos efekto, didelės unikalių tarpusavyje susijusių savybių įvairovės ir potencialo įvairiuose taikymuose. Dėl stiprios Jahn-Teller tipo elektron-fononinės sąveikos akustiniai metodai yra perspektyvūs tiriant manganitus. Šioje disertacijoje pateikiami nuotėkio paviršinių akustinių bangų spinduliuotės į tūrį sklidimo dariniuose La0.67Sr0.33MnO3 plėvelė –... [toliau žr. visą tekstą] / Acoustic wave and light – acousto-optic (AO) interaction provides an efficient tool for probing the acoustic wave properties not only at a crystal surface but also at any point within its bulk. This is topical in the design of the bulk wave devices for various applications. Meanwhile, there have been a few investigations of AO diffraction by (interdigital transducer) IDT-generated bulk waves, but not of the diffraction due to the radiation from leaky surface acoustic waves (SAWs). On the other hand, AO interaction enables efficient control of light parameters. Bulk wave AO devices have found numerous applications as light modulators, deflectors, tunable filters. In this PhD thesis, the experimental investigation and theoretical model of anisotropic light diffraction by leaky SAW radiation into crystal bulk in ZX-LiNbO3 and YX-LiTaO3 are reported. This type of interaction allows one to combine benefits of the IDT technology with the enhanced interaction efficiency of bulk-wave-type interaction. Mixed-valence perovskite manganites were studied intensively in recent years due to the observed paramagnetic to ferromagnetic transition at Curie temperature, colossal magnetoresistance effect, a variety of unique properties and potential at various applications. Due to the strong Jahn-Teller electron-phonon coupling the acoustic technique is effective tool for investigations of manganites. In this PhD thesis, the experimental investigation of the leaky SAW radiation propagating in... [to full text]

Acoustic wave and light – acousto-optic (AO) interaction provides an efficient tool for probing the acoustic wave properties not only at a crystal surface but also at any point within its bulk. This is topical in the design of the bulk wave devices for various applications. Meanwhile, there have been a few investigations of AO diffraction by (interdigital transducer) IDT-generated bulk waves, but not of the diffraction due to the radiation from leaky surface acoustic waves (SAWs). On the other hand, AO interaction enables efficient control of light parameters. Bulk wave AO devices have found numerous applications as light modulators, deflectors, tunable filters. In this PhD thesis, the experimental investigation and theoretical model of anisotropic light diffraction by leaky SAW radiation into crystal bulk in ZX-LiNbO3 and YX-LiTaO3 are reported. This type of interaction allows one to combine benefits of the IDT technology with the enhanced interaction efficiency of bulk-wave-type interaction. Mixed-valence perovskite manganites were studied intensively in recent years due to the observed paramagnetic to ferromagnetic transition at Curie temperature, colossal magnetoresistance effect, a variety of unique properties and potential at various applications. Due to the strong Jahn-Teller electron-phonon coupling the acoustic technique is effective tool for investigations of manganites. In this PhD thesis, the experimental investigation of the leaky SAW radiation propagating... [to full text] / Akustinių bangų ir šviesos – akustooptinė (AO) sąveika įgalina tirti akustinių bangų savybes ne tik kristalo paviršiuje, bet ir tūryje. Tai aktualu kuriant tūrinių bangų prietaisus įvairiems taikymams. Iki šiol yra atlikta keletas AO difrakcijos eksperimentų, kai sunertiniais keitikliais žadinamos tūrinės bangos, bet ne nuotėkio paviršinių akustinių bangų (PAB) spinduliuotė į tūrį. Kita vertus, AO sąveiką galima efektyviai panaudoti šviesos parametrų valdyme. Tūrinių bangų AO prietaisai – šviesos moduliatoriai, deflektoriai, derinami filtrai plačiai naudojami praktikoje. Šioje disertacijoje pateikiami anizotropinės šviesos difrakcijos nuotėkio paviršinių akustinių bangų spinduliuote į kristalo tūrį ZX-LiNbO3 ir YX-LiTaO3 eksperimentiniai rezultatai ir teorinis modelis. Tokio tipo sąveika įgalina suderinti sunertinių PAB keitiklių technologijos privalumus su didesniu šviesos sąveikos su tūrinėmis akustinėmis bangomis efektyvumu. Dėmesys mišraus valentingumo manganitams, turintiems perovskito kristalinę gardelę vis didėja dėl fazinio virsmo paramagnetikas – feromagnetikas Kiuri temperatūroje, milžiniškosios magnetovaržos efekto, didelės unikalių tarpusavyje susijusių savybių įvairovės ir potencialo įvairiuose taikymuose. Dėl stiprios Jahn-Teller tipo elektron-fononinės sąveikos akustiniai metodai yra perspektyvūs tiriant manganitus. Šioje disertacijoje pateikiami nuotėkio paviršinių akustinių bangų spinduliuotės į tūrį sklidimo dariniuose La0.67Sr0.33MnO3 plėvelė –... [toliau žr. visą tekstą]

Nous présentons un nouveau type d'imageur plénoptique appelé LOFI (Laser Optical Feedback Imaging). Le grand avantage de cette technique est qu'elle est auto-alignée, car le laser sert à la fois de source et de détecteur de photons. De plus, grâce à un effet d'amplification intra-cavité produit par la dynamique du laser, et grâce à un marquage acoustique des photons réinjectés, ce dispositif possède une sensibilité ultime au photon unique. Cette sensibilité est nécessaire si l'on veut réaliser des images à travers des milieux diffusants. L'autre intérêt présenté par le caractère plénoptique de notre imageur, est qu'il permet d'obtenir simultanément une double information: la position et la direction de propagation des rayons lumineux. Cette propriété offre des possibilités inhabituelles, comme celle de conserver la résolution d'un objectif de microscope bien au-delà de sa distance de travail, ou encore de pouvoir corriger par un post-traitement numérique les aberrations causées par la traversée d'un milieu hétérogène. Le dispositif LOFI plénoptique semble donc idéal pour une imagerie en profondeur à travers des milieux complexes, tels que les milieux biologiques. Les performances très intéressantes de cette imageur sont cependant obtenues au prix d'un filtrage spatial très coûteux en photons et au prix d'une acquisition des images réalisées point par point, donc relativement lente. / We present LOFI (Laser Optical Feedback Imaging). The main advantage of this technique is that it is auto-aligned, as the laser plays both the role of an emitter and a receiver of photons. Furthermore, thanks to an intra-cavity amplification effect caused by the laser dynamics and an acoustic tagging of re-injected photons, this setup reaches a shot noise sensitivity (single photon sensitive). This sensitivity is necessary if our aim is to make images through scattering media. The other interest, which comes from the plenoptic property of our setup, is that one have access to a complete information about light rays (position and direction of propagation). This property implies unusual possibilities like keeping a constant resolution beyond microscope objectives working distance or being able to numerically compensate, after acquisition, aberrations caused by the propagation through heterogeneous media. Our setup is thus ideal for deep imaging through complex media (turbid and heterogeneous) like biological ones. These interesting properties are achieved at the price of a spatial filtering degrading photon collection efficiency and of a point by point image acquisition which is slow.

The purpose of this paper is to assemble measurement chain dedicated to contactless measuring of acoustic fields emitted by test sources and to validate its results. At first author discusses possible optic methods which can be used to measure acoustic fields, then he talks about theoretical foundations which are needed to measure data and to reconstruct final data. The last two chapters are dedicated to cover basics about created program and to analyse various aspects which influence measured and reconstructed data. Created measurement chain is fully functional, at the end of this thesis are proposed some ways of improving