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Lower detection limit of the acousto-optic effect using Optical Feedback Interferometry

Lower detection limit of the acousto-optic effect using Optical Feedback Interferometry

Index Terms—Optical feedback, interferometry, self-mixing, acousto-optic effect. I. I NTRODUCTION Optical Feedback Interferometry (OFI) is a non-contact, high-precision sensing scheme which is applied to many domains of metrology. Today we find OFI in applications such as flowmetry, absolute distance measurements, vibrometry and velocimetry [1]–[6]. Compared to other non-contact sensing technologies, OFI is self-aligned, low cost and robust. Recent applications have applied the sensing scheme to the imaging of acoustic waves through the acousto-optic effect. Bertling et al [6] and Urgiles et al [7] create visual representations of stand- ing and propagating sound waves in air, while Dubois et al proposed an exciting application to image pressure waves in acoustic metamaterials [8].
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Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

To conclude, our results reveal for the first time, to our best knowledge, that it is possible to induce a conversion of light polarization with GHz coherent acoustic phonons in birefringent ferroelectrics such as LNO and BFO. Full experimental investigations have been conducted on various crystallographic orientations to clearly evidence the role of optical anisotropy. Our observations are fully supported by the theoretical framework of acousto-optic processes. These results could pave the way of next- generation GHz acousto-optic polarization converter devices with attractive perspectives at the nanoscale. As a direct consequence, we show that an all-optical device for ultrafast manipulation of the light information can be developed by using short laser pulse for launching in ferroelectric media coherent GHz acoustic phonons capable to modify light polarization. Such a device can benefit from the wide knowledge developed on LNO material for its optical properties and be rapidly tested for practical applications. As further direction, we believe that exploring ultrafast acousto-optic effect in ferroelectrics with GHz surface acoustic waves (SAWs) would certainly offer new applications, although current limitations for the generation (detection) of very high frequency SAWs exist, such as the lateral optical diffraction limit for focusing the pump (probe) laser beams. This needs to be overcome to reach the high frequency regime and some alternatives based on surface nanostructurations have been recently reported 42,43 .
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Acousto-optic and photoacoustic imaging of scattering media using wavefront adaptive holography techniques in NdYO4

Acousto-optic and photoacoustic imaging of scattering media using wavefront adaptive holography techniques in NdYO4

1. Introduction Tagging photons with ultrasound is an attractive method to image the optical properties inside multiple-scattering media such as biological tissues [1]. Indeed, conventional optical imaging techniques cannot be used on biological tissues because they rely on ballistic light, which is attenuated very fast in such media due to a very high scattering coef•cient. A way to harvest in- formation from the diffused light is to couple it with ultrasound (US) through the acousto-optic effect. As the US at some MHz are ballistic inside most biological tissues, it is possible to focus them in a small volume thus creating a small virtual source of ultrasonically tagged photons. These so called tagged photons are slightly shifted in frequency, due to the US phase modula- tion. Then, with an appropriate detection, it is possible to probe the local optical properties of the sample by scanning the focus spot of the US within the sample. As an increase of the tagged photons results in a decrease of the untagged photons and vice versa, the information from the acousto-optic signal can be retrieved on either component. The resolution of this acousto-optic imaging technique, given by the size of the virtual tagged photons source, is connected to the size of the acoustic focal spot (typically 1 mm at echographic frequencies), whereas the contrast of the image is given by the intensity of light at the US focal point which means that it is of optical nature.
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Magneto-optic detection limits for semiconductor spintronics

Magneto-optic detection limits for semiconductor spintronics

Despite the fact that the Sagnac interferometer configuration has equal or inferior FOM as compared to the PCP and OB techniques, it was nevertheless interesting for us to investigate it in detail. It is usually used to separate the rotations arising due to the Faraday effect, which is a nonreciprocal phenomenon, from those arising due to reciprocal linear birefringence (Spielman et al., 1990 ). This still can be achieved with other, one path techniques such as PCP or OB, but it would require at least two separate measurements, where, for example, the sample is measured once and then remeasured after π rotation around an axis perpendicular to the light propagation direction. Such separated in time measurements are usually hard to achieve under the exact same experimental conditions, or with the sample which is spatially in- homogeneous. The two path nature of Sagnac interferometers guarantees that the same part of the sample is sensed, since the collinearity of clockwise and counter- clockwise propagating beams is ensured by the interference on the detector.
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en fr Macroscopic and acousto-mechanic analogy of gas microbubble:: application to ultrasound contrast agents Analogie macroscopique et acousto-mécanique d'une microbulle: : application aux agents de contraste ultrasonore

Nous proposons d’étudier le comportement oscillatoire d’une microbulle via un système acousto-mécanique de pendules couplés paramétriquement excités par une force verticale. En effet, lorsqu’elles sont soumises aux ultrasons, les microbulles (1-8 µm) présentent une dynamique riche et complexe qui peut être dé- crite par un réseau d’oscillateurs couplés. Il s’agit de comprendre la dynamique d’une bulle unique pour l’étudier ensuite dans des conditions expérimentales et cliniques pour des applications en imagerie et en thérapie. L’objectif est de décrire l’évolution, l’apparition et les conditions expérimentales d’instabilité du mode radial faisant apparaître les modes de vibration décrits à partir des harmoniques sphériques. Dans un premier temps, un état de l’art comparant les différents modèles mathématiques des ACUs a motivé notre étude sur l’analogie entre une microbulle et une chaîne de pendules. Dans un second temps, nous avons montré que les deux systèmes sont décrits par une équation de Mathieu. D’un point de vue expérimental, nous avons développé la chaîne de pendules. Celle-ci consiste en un cercle d’aluminium sur lequel sont fixés des pendules à l’aide de fil de nylon. La chaîne de pendules repose sur le système d’excitation qui génère une excitation sinusoïdale variant de 1 Hz à 5 Hz. Les résultats obtenus ont été confirmés par une étude numérique et montrent un comportement similaire entre la chaîne de pendules et une microbulle. Nous avons noté l’apparition de modes de vibration dont certains oscillant à des fréquences sous-harmoniques. L’utilisation de ce système macroscopique a permis d’extraire des informations qui seront exploitées pour une utilisation optimale des agents de contraste en imagerie et thérapie.
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Acousto-optic laser optical feedback imaging

Acousto-optic laser optical feedback imaging

OCIS Codes: OCIS Codes:, (110.4280) , (110.3175) , (280.3420) Context Imaging objects through or embedded within a scattering media is a challenging problem linked to many medical applications such as cancer detection. The main challenge is to realize images through a turbid medium with both a high resolution and good signal to noise ratio (SNR). The information needed to obtain diffraction-limited images is carried by ballistic photons. However compared to scattered photons their number rapidly decreases with the depth, which dramatically reduces the SNR. Consequently, imaging through scattering media with diffraction-limited resolution requires both the detection of ballistic photons and the rejection of the scattered light. The filtering of the scattered light is generally achieved by limiting the depth of focus of the imaging setup. Efficient methods for accomplishing this goal include confocal microscopy [1], time resolved techniques [2] and optical coherent microscopy [3]. However, the thickness of the scattering medium explored with these techniques is limited to about twenty mean free paths and these methods require a high optical power in the medium to compensate for the losses in ballistic photons, which is often not compatible with medical application. To image deeper with a “good” SNR, there is a great interest in using the scattered photons since they decrease much slower than the ballistic ones. In this case, a millimetric resolution can be obtained by acoustic tagging of the scattered photon with a focalized ultrasonic wave, as in Acousto-Optical Coherence Tomography (AOCT) [4]. LOFI technique and imaging through turbid media We propose to use the LOFI technique while focalizing an ultrasonic (US) wave in a scattering media in order to image embedded object with a diffraction-limited resolution. LOFI is an ultrasensitive laser autodyne interferometer and also a confocal imaging technique combining the great accuracy of optical interferometry with the very high sensitivity of class B lasers to optical feedback [5].In this autodyne method, the optical beating between a reference wave and the signal wave (the light
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Correlative Compositional Analysis of Fiber-Optic Nanoparticles

Correlative Compositional Analysis of Fiber-Optic Nanoparticles

Correlative Compositional Analysis of Fiber-Optic Nanoparticles H. Francois-Saint-Cyr 1 , I. Martin 1 , W. Blanc 2 , P. LeCoustumer 3 , C. Hombourger 1 , D. Neuville 4 , D. J. Larson 1 , T. J. Prosa 1 , C. Guillermier 5 1 CAMECA Instruments Inc., 5500 Nobel Drive, Suite 100, Madison, WI, 53711, USA 2 Université Nice Sophia Antipolis, CNRS, LPMC, UMR7336, 06100 Nice, France

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Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

On the other hand, the Lorentz force electrical impedance tomography (LFEIT) method [Montalibet et al., 2001, Grasland-Mongrain et al., 2013], also known as magneto- acousto electrical tomography [Haider et al., 2008], is a medical imaging technique producing electrical conductivity images of tissues [Wen et al., 1998, Roth, 2011, Ammari et al., 2014]. With this technique, an ultrasound wave is transmitted by an acoustic transducer in a biological tissue placed in a magnetic field. The movement of the tissue in the magnetic field due to the ultrasound propagation induces an electric current due to Lorentz force. The measurement of this current with electrodes in contact with the sample allows to reconstruct images of electrical impedance interfaces.
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Fiber-optic sensors monitor FRP-reinforced bridge

Fiber-optic sensors monitor FRP-reinforced bridge

Figures 5 and 6 show typical data recorded by FOS instalied on the CFRP grid reinforcement and in the concrete of the bridge deck. The variation of recorded[r]

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Design of Excess 3 to BCD code converter using electro-optic effect of Mach-Zehnder Interferometers for efficient data transmission

Design of Excess 3 to BCD code converter using electro-optic effect of Mach-Zehnder Interferometers for efficient data transmission

Keywords: Electro-optic effect; Mach-Zehnder interferometer; Beam Propagation Method, optical computing, Excess 3 code, BCD code. 1. INTRODUCTION Digital arithmetic plays an imperative role in the design of digital processors, signal processing, and communications to achieve fast computation, less processing time, high system efficiency and data speed [1]. However, as the hunger of high speed data requirement is increasing day by day hence ultra fast computation is also becomes viable. To achieve future requirements, researchers have shown great interest to implement sequential and combinational logic circuits in all optics [2-15] such as full adder [2], multiplier [3], shift registers [4], synchronous up counter [5], encoder [6], comparators [7], and code converters[8]. There are various methods to implement all optical circuits i.e. Micro- electromechanical systems (MEMS) [9], terahertz optical asymmetric de-multiplexer (TOAD) [10], non-linear material (NLM) [11], semiconductor optical amplifier based M ach - zehnder interferometers (SOA-MZI) [12], cross-gain modulation (XGM) effect [13], cross-phase modulation (XPM) effect of SOA based MZI [14], and LiNbO3 based MZI [15]. Here an optical Excess 3 code to BCD converter using electro-optic effect [15] in LiNbO3 based MZI is proposed. LiNbO 3 seems to be a promising solution, because of its characteristic features of compact size, thermal stability [16],
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Correlative Compositional Analysis of Fiber-Optic Nanoparticles

Correlative Compositional Analysis of Fiber-Optic Nanoparticles

Correlative Compositional Analysis of Fiber-Optic Nanoparticles H. Francois-Saint-Cyr 1 , I. Martin 1 , W. Blanc 2 , P. LeCoustumer 3 , C. Hombourger 1 , D. Neuville 4 , D. J. Larson 1 , T. J. Prosa 1 , C. Guillermier 5 1 CAMECA Instruments Inc., 5500 Nobel Drive, Suite 100, Madison, WI, 53711, USA 2 Université Nice Sophia Antipolis, CNRS, LPMC, UMR7336, 06100 Nice, France

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Acousto-optical coherence tomography with a digital holographic detection scheme

Acousto-optical coherence tomography with a digital holographic detection scheme

θ≈1° Fig. 1. (Color on-line) Experimental set-up. HWP: half-wave plate, PBS: polarizing beam splitter, AOM1, AOM2: acousto-optic modulators, FI: Faraday isolator, UT: ultrasound transducer, fC: camera framerate, fL: laser frequency. In the tank, the scheme axes are modified in order to give a view of the inside.

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Acousto-optical imaging using a powerful long pulse laser

Acousto-optical imaging using a powerful long pulse laser

/ La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. For the publisher’[r]

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Évaluation acousto-ultrasonique de l'endommagement thermique dans un matériau composite carbone/époxyde

Évaluation acousto-ultrasonique de l'endommagement thermique dans un matériau composite carbone/époxyde

Deux des plus importants parametres de la propagation des ondes sont la dispersion et Vattenuation [15, 20]. La dispersion resulte du fait que Ie materiau n'est strictement pas homogene.[r]

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Linear Electro Optic Effect for High Repetition Rate Carrier Envelope Phase Control of Ultra Short Laser Pulses

Linear Electro Optic Effect for High Repetition Rate Carrier Envelope Phase Control of Ultra Short Laser Pulses

medium of length, L, which is non-centrosymmetric and exhibits a Pockels effect. This is, for example, the case [17,20] in LiNbO 3 —uniaxial crystal, crystalline class 3 m or RTP-biaxial crystal orthorhombic crystalline class mm2—when choosing appropriate directions for the linearly polarized laser field and the applied static electric field. Figure 1 illustrates how the direction of propagation and the polarization of light are to be chosen in practice and how the voltage is to be applied on the crystal in two interesting cases, LiNbO 3 and RTP. X, Y and Z are the principal dielectric axes, which are parallel to the
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Imagerie acousto-optique de milieux diffusants épais par détection photoréfractive

Imagerie acousto-optique de milieux diffusants épais par détection photoréfractive

La Tomographie Acousto-Optique Cohérente Obtenir une résolution axiale pour l’imagerie acousto-optique suppose de différencier les lieux du marquage acousto-optique. Pour ce faire, les recherches menées dans le domaine de l’imagerie acousto-optique ont déjà apporté des élé- ments de réponse à travers plusieurs techniques, qui se basent sur des régimes d’excitation ultrasonore continue ou impulsionnelle. Dans la première section de ce chapitre, seront exposées les principales techniques déjà élaborées. A la suite de cela sera présentée, dans la deuxième section, la nouvelle approche que nous proposons et que nous appelons la tomographie acousto-optique cohérente (TAOC). Nous verrons que cette technique se base sur la création d’une zone différenciée particulière, appelée zone de cohérence acousto-optique, qui s’ap- puie sur une modulation aléatoire de phases du bras acoustique et de l’un des bras optiques. La troisième section présentera une modélisation de la TAOC, appliquée à notre détection holographie photoréfractive. Dès lors, seront pré- sentées les résultats expérimentaux. La quatrième section se chargera d’abord de présenter le montage expérimental. La cinquième section sera consacrée à la mise en évidence de la résolution axiale obtenue par la TAOC. La sixième et dernière section présentera des imageries expérimentales de milieux diffusants épais, résolues axialement.
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Monitoring trabecular bone microdamage using a dynamic acousto-elastic testing method

Monitoring trabecular bone microdamage using a dynamic acousto-elastic testing method

an actual microdamage) when the |b| value was higher than 50. Results could have been presented as { L  L sample  | ð DTOFM=Dp LF Þ only, but these would then be difficult to compare with data found in the literature. Thus, |b| values less than 50 characterize classical NL behaviour (microdamage might be too weak to be detected with DAET). In contrast, the |b| value higher than 50 cannot be explained only by a high material velocity value but is related to non- classical non-linearity and is very probably due to microdamage. The NL behaviour was mostly asso- ciated with hysteresis, asymmetry, and significant dissipative non-linearity, characterizing non-classi- cal non-linearity due to microcracks. These findings were always correlated with histology (sample 7, sample defatted by trichloroethylene, and sample Z). All measurements were performed at least twice for each sample. DAET reproducibility was good for samples with low levels of non-linearity (|b| , 50, |TOFM| , 3 ns). In samples exhibiting high levels of non-linearity (|b| . 50), DAET reproducibility was sample dependent. Some samples showed fairly constant behaviour from one test to the other, and others presented increased or decreased NL beha- viour from one test to another. This can be partly explained by the well-known conditioning effect in damaged materials (viscoelastic memory effects). The NL response due to LF stress depends on the whole stress history of the sample. In future experiments particular care will be taken with DAET measurements, to take into account these possible conditioning effects.
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Optical spectroscopy investigation of fiber optic
high temperature sensors.

Optical spectroscopy investigation of fiber optic high temperature sensors.

Optical fibers have become an integral part of our daily life in a variety of appli- cations, most notably in telecommunications and non-invasive medical diagnostics. Derived products, including fiber Bragg gratings (FBGs) extend the field of appli- cations to e.g. temperature and strain sensors that are already beyond the labo- ratory proof-of-concept level and that hold the promise to transform many areas of industries in an ever increasing number of applications in aerospace, structural integrity monitoring as well as in-site sensing in turbines and reactors. Especially the latter represent a harsh environment which makes the use of electronic sensors either completely impossible or which implies short service intervals. Often these industries employ optical techniques to conduct measurement in the optical fibers themselves, e.g. based on evanescent fields but only a few fiber-based techniques allow for distributed multiplexed sensing. The idea is to operate different sensors along the length of the fiber at different wavelengths, a concept that also capitalizes on the fact that most optical sensors are passive so that the fiber only carries the signal rather than the power supply. The aforementioned points translate into the many advantages of fiber based sensors: reliability, good sensitivity, multiplexing, and low maintenance costs so that in many industries, the technology is now already seen as a worthwhile alternative to established electronic sensors. Optical fibers are immune to electromagnetic field (EMI), compact and can be functionalized. This collaborative dissertation with an industrial partner specialized in developing prac- tical, end–user–focused commercial sensor solutions, is based largely on fiber optic sensing. While the overall project dealt with glass fiber and Fiber Bragg Gratings (FBG) for temperature sensing at elevated temperature and in otherwise harsh en- vironment, the focus of my work is on the physics and material science of FBGs at elevated temperatures.
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Longitudinal effects of an optic nerve injury on visual behaviour

Longitudinal effects of an optic nerve injury on visual behaviour

Prevalent causes of visual impairment include cataracts, age-related macular degeneration, diabetic retinopathy, and glaucoma (Congdon et al., 2004; Roodhooft, 2002). These ocular diseases, affecting the eye and optic disc, have long been the focus of our understanding of visual impairment. With ocular diseases, cortical processing within the brain remains relatively intact, and the visual stimuli are simply not received by the cells in the eye and, consequently, the brain (Martin et al., 2016). However, when damage occurs at the level of transmission and/or processing in the brain, this typically leads to perceptual deficits that have more complex consequences yet to be fully understood (Dutton, 2003). These neurological deficits of the visual system are the primary focus of the present thesis as they cause devastating vision loss with very few treatment options available. In order to treat such deficits, it is important to first understand the progression of the deficit and then potentialize the mechanisms of recovery. To this end, rodents have become increasingly popular models for studying visual deficits and recovery, as used in the present study.
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Review of fiber optic diagnostic techniques for power transformers

Review of fiber optic diagnostic techniques for power transformers

2. Background on Fiber Optic Sensors An optical fiber is basically a cylindrical symmetric structure comprising a central “core” with a 4 to 600 μm diameter between and characterized by a uniform refractive index [6]. An optical cladding with a relatively low refractive index then surrounds the optical fiber. The light waves carried in the core by reflection at the interface between the core and the optical cladding are thus trapped [7]. An external plastic coating is used to cover the cladding, providing environmental and mechanical protection to the fiber. Fundamentally, an optical source coupled to a fiber optic transmission line constitutes the fiber optic sensors. This source directs the radiation towards the head of a sensor [8]. As the medium is optics, i.e., light, no electronics is required in the long-range transmission of sensor data, hence their viability for remote sensing applications. An optical fiber sensor comprises the following elements: an optical fiber, a sensing component, a detector, and a light source. It operates in such a way that some parameter of the optical system (wavelength, phase, polarization, intensity, etc.) intensity is modulated by the sensing element, which produces a change in the characteristics of the optical signal at the detector. The main idea is to measure an external physical parameter by inducing changes in one or more of the optical properties of the light beam travelling inside the optical fiber [9]. So, the fiber is simultaneously the transmission medium and the sensing element. Fiber optic sensors are classified as intrinsic or extrinsic according to their location [10]. If the modulation occurs in the fiber, it is intrinsic. It is considered extrinsic if the modulation is made through an external transducer.
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