Com a crescente disponibilidade de luz síncrotron tem-se utilizado cada vez mais a dispersão anômala (f´) no estudo de materiais. Apesar dos vários métodos já empregados na medida do fator de espalhamento atômico, ainda é pequeno o número de elementos abrangidos. Este trabalho apresenta uma contribuição à ampliação da gama de elementos mensuráveis através de um método interferométrico diferencial para a determinação experimental de f´. A sua demonstração é feita através de medidas em Selênio obtendo-se o mesmo nível de precisão do método &#933-&#933/2 usado em trabalhos anteriores. Esses dois métodos são criticados quanto ao limite de erro atingível devido à sua natureza não-absoluta. Uma técnica de preparação de amostras para materiais de baixo ponto de fusão é explorada, permitindo determinar f´absolutamente, com erro de 0,03 elétron. A medida do fator de espalhamento atômico através do desvio angular entre as reflexões de Bragg e Laue é proposta e testada com resultados de qualidade bastante inferior às técnicas interferométricas. A construção de interferômetros de raios X estáveis e de alto contraste é estudada quanto à seleção dos monocristais de silício e tratamento após o corte do dispositivo, atingindo-se contraste de 80% com estabilidade de uma milifranja por hora. / The use of anomalous dispersion (f\') in the study of materials has been increasing with the availability of synchrotron radiation. Although many methods have been designed for the measurement of the atomic scattering factor, the number of elements the cover is still small. This work presents a contribution to the widening of the range of measurable elements through a Differential interferometric method for the determination of f´. Its demonstration is achieved by measurements on Selenium, reaching the same level of accuracy obtained by the &#933-&#933/2 method used in previous work. These two methods are criticized in terms of the achievable errors due to its non-absolute nature. A technique for the preparation of samples with low melting point materials is developed, allowing the determination of f´ absolutely, with an error of 0,03 electron. The measurement of atomic scattering factor through the angular offset between Bragg and Laue reflections is proposed and tested, with low quality results compared to interferometric methods. The construction of high stability and good contrast X-ray interferometers is studied in terms of silicon single crystal selection and its treatment after device cutting. 80% contrast was achieved with a stability of one milifringe per hour.

Dans cette thèse, nous avons mis en oeuvre un système de mesure de distance absolue (Absolute Distance Measurement, ADM) de haute précision utilisant l'interférométrie à balayage de fréquence (Frequency Sweeping Interferometry, FSI). La technique FSI exige que la plage de réglage de fréquence du laser balayé soit mesurée avec une précision élevée, ce qui est difficile en raison de l'absence d'un moyen simple de mesurer la haute fréquence d'un laser en temps réel. Dans cette thèse, un peigne de fréquence a été utilisé comme règle de fréquence lumière pour mesurer la plage de réglage de la fréquence du laser à balayage. Un peigne de fréquence formé par un laser femtoseconde est constitué de millions de lignes de peigne régulièrement espacées, ce qui permet de le considérer comme une règle de fréquence de la lumière. La calibration de fréquence a été réalisée en filtrant le signal hétérodyne entre le laser à balayage et les lignes de peigne en utilisant un filtre passe-bande étroit. Cette approche nous permet de détecter le signal d'étalonnage lorsque la fréquence du laser à balayage est proche d'une ligne en peigne. Etant donné que l’intervalle de fréquence entre les lignes de peigne peut être mesuré avec précision ou activement verrouillé en phase par rapport à un oscillateur radiofréquence (RF) stable, la plage d ’ accord du laser à balayage peut être mesurée avec une grande précision. En particulier, chacun des deux pics d’étalonnage peut être utilisé dans le calcul de la distance, ce que nous appelons des «sous-mesures» en un seul balayage. Combinée au grand nombre de lignes de peigne, la moyenne des sous-mesures améliore considérablement la précision des mesures sans balayage multiple. Dans la thèse, la condition de détection et les caractéristiques du signal hétérodyne entre le laser à balayage et la ligne de peigne sont présentées. Une conception de filtre pour filtrer le signal hétérodyne est réalisée. Un travail de modélisation concernant l'effet du bruit de phase des lasers sur la distorsion d'enveloppe du pic d'étalonnage a été présenté. Des travaux expérimentaux basés sur les concepts de mesure ont été réalisés. Il montre que l'utilisation du schéma de mesure proposé peut considérablement améliorer la précision de la mesure de distance. Dans l’une des mesures, une précision de 30 nm pour une distance d’environ 0,8 m, correspondant à une incertitude relative de 37 ppm (part-perbillion) a été obtenue. Le résultat a été obtenu sur la base d'une méthode de traitement du signal de comptage de franges. La grande précision a été obtenue grâce au grand nombre de sous-mesures et à la stabilité des lignes de peigne régulièrement espacées. Nous avons constaté que la mesure de vibration de la cible peut également être effectuée en prenant avantage des lignes de peigne denses. Une sensibilité élevée, limitée à 1,7 nm efficace en bruit, de la mesure des vibrations a été atteinte. Ce résultat nous permet de surveiller la vibration de la cible, ce qui est un problème important de la technique FSI. / In this thesis, we implemented a high-precision absolute distance measurement (ADM) system using frequency sweeping interferometry (FSI). The FSI technique requires the frequency tuning range of the swept laser to be measured with high accuracy and precision, which is challenging due to the lack of an easy way to measure the high frequency of a laser in real time. In this thesis, a frequency comb has been used as the light frequency ruler for measuring the frequency tuning range of the sweeping laser. A frequency comb formed by a femtosecond laser consists millions of evenly spaced comb lines so that can be regarded as a light frequency ruler. The frequency calibration was realized by filtering the heterodyne signal between the sweeping laser and the comb lines using a narrow bandpass filter. This approach allows us to detect the calibration signal when the frequency of the sweeping laser is in the vicinity of a comb line. As the frequency interval between the comb lines space can be precisely measured or actively phase-locked against a stable radio-frequency (RF) oscillator, the tuning range of the sweeping laser could be measured with high accuracy. Especially, each two calibration peaks can be used in the calculation of distance, which we call sub-measurements in a single sweeping. Combined with the large number of the comb lines, averaging of the sub-measurements improves greatly the measurement precision without multiple sweeping. In the thesis, the condition of detecting and the characteristics of the heterodyne signal between the sweeping laser and the comb line are presented. A filter design for filtering the heterodyne signal is performed. A modeling work concerning the effect of the phase noise of lasers on the envelope distortion of the calibration peak has been presented. Experimental works based on the measurement concepts have been carried out. It shows that using the proposed measurement scheme can greatly improve the distance measurement precision. In one of the measurements, a precision of 30 nm for a distance around 0.8 m, corresponding to 37 ppb (part-per-billion) relative uncertainty has been achieved. The result was obtained based on a fringe counting signal processing method. The high precision was obtained thanks to the large number of sub-measurements and the stability of the evenly spaced comb lines. We have found that vibration measurement of the target can be also performed taking the advantage of the dense comb lines. A high sensitivity, limited by 1.7 nm noise RMS, of vibration measurement has been achieved. This result allows us to monitor the vibration of the target, which is an important issue of FSI technique.

Ce travail de thèse est une contribution au développement des méthodes d’acoustique non linéaire pour le contrôle non destructif et l’imagerie de défauts de type contact dans les solides.Dans ce travail, des modifications sont proposées pour deux méthodes récentes de contrôle non destructif par acoustique non linéaire : l’interférométrie de coda couplée au retournement temporel, et l’imagerie non linéaire par ultrasons aériens. Le principal avantage de la première méthode est sa sensibilité extrême liée à l’accumulation des effets induits par des changements, même faibles, des propriétés de l’échantillon durant la formation de la coda. La deuxième méthode apporte une approche complémentaire en permettant de réaliser un contrôle sans contact. Les techniques développées ont été testées sur des échantillons présentant des défauts artificiels à des emplacements connus. Les performances de chacune des méthodes ont été étudiées.La deuxième partie de ce travail porte sur la description théorique des non-linéarités acoustiques de contact et leur utilisation pour le développement d’une boite à outils numériques permettant la simulation d’ondes acoustiques dans des structures complexes contenant des contacts internes. Un model physique décrivant le décalage tangentiel de deux corps en contact en présence de friction est proposé. Il aboutit à une solution analytique pour la relation présentant une hystérésis entre les déplacements de contact normal et tangentiel et les chargements. Ce modèle est utilisé comme condition aux frontières pour les surfaces de contact internes (défauts) dans un modèle de propagation d’ondes acoustiques utilisant un logiciel d’éléments finis commercial / This PhD thesis work contributes to the development of nonlinear elastic methods for non-destructive testing and imaging of contact-type defects in solids.In this work, two modifications of recent nonlinear nondestructive testing methods are suggested: the coda wave interferometry combined with the nonlinear time reversal principle and air-coupled nonlinear ultrasonic imaging. The principal advantage of former technique is in its extremely high sensitivity owing to the fact that weak changes in sample's parameters are accumulated and finally greatly amplified during the formation of the coda wave. The other technique has a complimentary strength and offers a possibility of a remote detection. The developed techniques are tested on samples with artificially fabricated defects at known locations. The performance of each method is accessed and the potential for obtaining robust nonlinear images is demonstrated.The second part of the work is concerned with a theoretical description of contact acoustical nonlinearity and its use for creating of a numerical toolbox capable of simulating wave propagation in complex structures containing internal contacts. A physical model describing the tangential shift of two contacting bodies in the presence of friction has been proposed. Its result is an analytical computer-assisted solution for hysteretic relationships between normal and tangential contact displacements and loads. The contact model and derived load-displacement relationships are used as boundary conditions posed at the internal boundaries (contact surfaces) in a finite element wave propagation model programmed via commercial software

L"étude de la transition entre les disques proto-planétaires riches en gaz et les disques de débris, dans lesquels le gaz a disparu au bout de quelques millions d'année, est essentielle pour contraindre les mécanismes de formation planétaire. De plus en plus de disques de débris riches en gaz sont détectés. Certains de ces disques possèdent même des caractéristiques qui laissent présumer que le gaz y est d'origine primordiale à la différence de la poussière. C'est à ces diques hybrides que je m'intéresse tout particulièrement dans cette thèse. Grâce aux interféromètres ALMA et NOEMA, j'ai pu observer en détails le disque de débris autour de l'étoile HD 141569, de type spectral A0V, âgée d'une dizaine de millions d'années. Mes observations révèlent un disque de gaz d'origine primordiale en cours de dissipation, ce qui fait de ce disque un système hybride. La poussière millimétrique y a aussi évolué, puisque son émission est faible et possède un indice spectral caractéristique de grains qui ont grossi. Afin de détecter de nouveaux disques hybrides, j'ai observé le gaz CO dans 25 disques de débris avec APEX et de 30 m de l'IRAM. Autour de HD 23642, le gaz semble être détecté à 4 sigma et pourrait correspondre à un disque singulier, puisqu'il entoure une binaire de l'amas Pléiades, dont l'âge est estimé à 125-130 millions d'années. Pour différents stades d'évolution des disques, l'émission du gaz et de la poussière est corrélée sauf pour les disques hybrides dont le rapport de flux est plus élevé, peut-être à cause une évolution rapide de la poussière. Il reste à savoir si cette phase est généralisable à tous les disques pour comprendre les imolications de ce phénomène. / The study of the transition between proto-planetary gas-rich disks and debris disks, where gas has disappeared in a few millions years, is crucial to constrain the planet formation mechanisms. More ans more gas-rich debris disks are detected. I have studied some of those disks where observations suggest that gas is still primordial. Thanks to radio interferometers suche as ALMA and NOEMA, i have observed in details the debris disk around the ten millions year okd HD 141569 star, of spectral type A0V. My observations reveal the gas disk is primordial and is dissipating, which makes the disk a hybrid system. The milimeter dust has also evolved, since its emission is weak and has e spectral index beta typical of large grains. To detect more hybrid disks, i have observed th CO gas in 25 disks with APEX and the IRAM 30 m. Around HD 23642, CO emission is detected at 4 sigma and coukd correspond to a peculiar disk, since it surrounds binary stars in the Pleiades cluster, which age is estimate around 125-130 millions years. The emission of the gas and dust is correlated for all types of disks but hybrids, where the high flux ratio might be due to a rapid dust evolution. It remains to know whether this phase is common to all disks to understand the implications of this phenomenon.

La recherche développée durant cette thèse constitue la première étape de développement d’une nouvelle méthodologie de détection sans marquage à l’échelle d’une goutte : un nouveau mécanisme de transduction est développé, basé sur l’actuation par électromouillage bi-fréquence d’un réseau d’ondes capillaires à la surface d’une goutte. La résonance capillaire de la goutte est étudiée par détection interférométrique de son apex en mouvement.La faisabilité de cette méthodologie est prouvée en caractérisant la cinétique d’évaporation de la goutte par glissement spectral des ondes capillaires.La deuxième partie de la thèse porte sur la modélisation du transport de biomolécules tensioactives dans une goutte : le transport diffusif, les processus d’ad/désorption aux surfaces, la condition cinématique d’un rayon variable(évaporation) ainsi qu’une quantité molaire finie de biomolécules sont pris en compte. Un nouveau nombre adimensionnel est proposé pour rendre compte de la taille finie d’une goutte. Puis le transport chimique associé au courant de dérive induit par les ondes capillaires (excitées par électromouillage oscillatoire)est pris en compte à l’aide de simulations numériques. Finalement,l’électromouillage haute et basse fréquence est appliqué au cas d’une goutte enrichie par des molécules d’albumine de sérum bovin. En utilisant conjointement l’interférométrie optique et l’imagerie, et en considérant la loi de Lippmann-Young, le vieillissement biochimique de la surface solide mouillée par la goutte est détecté. / This PhD research is thought of as a first step towards label freedigital biosensing. A novel transduction mechanism is developed, based on thegeneration of capillary waves along a drop surface induced by dual-frequencyelectrowetting. Acapillary resonance is measured by interferometry at the movingdrop apex. Aproof of concept of this electro-optical methodology for furtherintegration in a digital microsystem is given with characterization of drop evaporationkinetics. A second part focuses on modeling and numerical calculationsof the transport of surface active biomolecules in the drop. The model includesdiffusion, ad-/desorption phenomena together with a kinematic condition of avariable drop radius (evaporation) as well as a finite molecular amount of surfaceactive biomolecules. A dimensionless number is suggested to take into accountfinite size effects. Drop steady streaming due to oscillating electrowetting isfinally taken into account. Low- and high-frequency electrowetting is appliedto a drop laden with bovine serum albumin. By jointly using interferometry andimaging, enhancement of surface ageing is made evident under electrowetting.

In this thesis we investigate advanced techniques for the readout and control of various interferometers. In particular, we present experimental investigations of interferometer configurations and control techniques to be used in second generation interferometric gravitational wave detectors. We also present a new technique, tilt locking, for the readout and control of optical interferometers. ¶ We report the first experimental demonstration of a Sagnac interferometer with resonant sideband extraction (RSE). We measure the frequency response to modulation of the length of the arms and demonstrate an increase in signal bandwidth of by a factor of 6.5 compared to the Sagnac with arm cavities only. We compare Sagnac interferometers based on optical cavities with cavity-based Michelson interferometers and find that the Sagnac configuration has little overall advantage in a cavity-based system. ¶ A system for the control and signal extraction of a power recycled Michelson interferometer with RSE is presented. This control system employs a frontal modulation scheme requiring a phase modulated carrier field and a phase modulated subcarrier field. The system is capable of locking all 5 length degrees of freedom and allows the signal cavity to be detuned over the entire range of possibilities, in principle, whilst maintaining lock. We analytically investigate the modulation/demodulation techniques used to obtain these error signals, presenting an introductory explanation of single sideband modulation/demodulation and double demodulation. ¶ This control system is implemented on a benchtop prototype interferometer. We discuss technical problems associated with production of the input beam modulation components and present several solutions. Operation of the interferometer is demonstrated for a wide range of detunings. The frequency response of the interferometer is measured for various detuned points and we observe good agreement with theoretical predictions. The ability of the control system to maintain lock as the interferometer is detuned is experimentally demonstrated. ¶ Tilt locking, a new technique to obtain an error signal to lock a laser to an optical cavity, is presented. This technique produces an error signal by efficient measurement of the interference between the TEM00 and TEM10 modes. We perform experimental and theoretical comparisons with the widely used Pound-Drever-Hall (PDH) technique. We derive the quantum noise limit to the sensitivity of a measurement of the beam position, and using this result calculate the shot noise limited sensitivity of tilt locking. We show that tilt locking has a quantum efficiency of 80%, compared to 82% for the PDH technique. We present experimental demonstrations of tilt locking in several applications including frequency stabilisation, continuous-wave second harmonic generation, and injection locking of a Nd:YAG slab laser. In each of these cases, we demonstrate that the performance of tilt locking is not the limiting factor of the lock stability, and show that it achieves similar performance to the PDH based system. ¶ Finally, we discuss how tilt locking can be effectively applied to two beam interferometers. We show experimentally how a two beam interferometer typically gives excellent isolation against errors arising from changes in the photodetector position, and experimentally demonstrate the use of tilt locking as a signal readout system for a Sagnac interferometer.

<p>This doctoral thesis summarizes research in quantum cryptography done at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology (NTNU) from 1998 through 2007.</p><p>The opening parts contain a brief introduction into quantum cryptography as well as an overview of all existing single photon detection techniques for visible and near infrared light. Then, our implementation of a fiber optic quantum key distribution (QKD) system is described. We employ a one-way phase coding scheme with a 1310 nm attenuated laser source and a polarization-maintaining Mach-Zehnder interferometer. A feature of our scheme is that it tracks phase drift in the interferometer at the single photon level instead of employing hardware phase control measures. An optimal phase tracking algorithm has been developed, implemented and tested. Phase tracking accuracy of +-10 degrees is achieved when approximately 200 photon counts are collected in each cycle of adjustment. Another feature of our QKD system is that it uses a single photon detector based on a germanium avalanche photodiode gated at 20 MHz. To make possible this relatively high gating rate, we have developed, implemented and tested an afterpulse blocking technique, when a number of gating pulses is blocked after each registered avalanche. This technique allows to increase the key generation rate nearly proportionally to the increase of the gating rate. QKD has been demonstrated in the laboratory setting with only a very limited success: by the time of the thesis completion we had malfunctioning components in the setup, and the quantum bit error rate remained unstable with its lowest registered value of about 4%.</p><p>More than half of the thesis is devoted to various security aspects of QKD. We have studied several attacks that exploit component imperfections and loopholes in optical schemes. In a large pulse attack, settings of modulators inside Alice's and Bob's setups are read out by external interrogating light pulses, without interacting with quantum states and without raising security alarms. An external measurement of phase shift at Alice's phase modulator in our setup has been demonstrated experimentally. In a faked states attack, Eve intercepts Alice's qubits and then utilizes various optical imperfections in Bob's scheme to construct and resend light pulses in such a way that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Construction of such faked states using several different imperfections is discussed. Also, we sketch a practical workflow of breaking into a running quantum cryptolink for the two abovementioned classes of attacks. A special attention is paid to a common imperfection when sensitivity of Bob's two detectors relative to one another can be controlled by Eve via an external parameter, for example via the timing of the incoming pulse. This imperfection is illustrated by measurements on two different single photon detectors. Quantitative results for a faked states attack on the Bennett-Brassard 1984 (BB84) and the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols using this imperfection are obtained. It is shown how faked states can in principle be constructed for quantum cryptosystems that use a phase-time encoding, the differential phase shift keying (DPSK) and the Ekert protocols. Furthermore we have attempted to integrate this imperfection of detectors into the general security proof for the BB84 protocol. For all attacks, their applicability to and implications for various known QKD schemes are considered, and countermeasures against the attacks are proposed.</p><p>The thesis incorporates published papers [J. Mod. Opt. 48, 2023 (2001)], [Appl. Opt. 43, 4385 (2004)], [J. Mod. Opt. 52, 691 (2005)], [Phys. Rev. A 74, 022313 (2006)], and [quant-ph/0702262].</p>

<p>Optical coherence tomography is an imaging modality with an outstanding resolution. During the project, a time domain OCT system based on a Michelson fibre interferometer was implemented and put into operation. A super-luminescent diode with a centre wavelength of 1295nm and a bandwidth of 45nm was selected as light source and a linear variable delay line as reference. Basic tests were made on phantoms constructed of filter foils and on gel-like agar slices with optical properties similar to human tissue. It was shown that the achievable resolution was at least 36um and can be increased. The system can easily be enhanced to create two-dimensional images.</p> / <p>Optische Kohärenztomographie ist ein bildgebendes Verfahren mit einer hervorragenden räumlichen Auflösung. Im Laufe des Projekts wurde ein OCT-System basierend auf einem faseroptischen Michelson-Interferometer implementiert und in Betrieb genommen. Als Lichtquelle wurde eine Superlumineszenzdiode mit einer Mittenwellenlänge von 1295nm und einer Bandbreite von 45nm gewählt. Eine variable optische Verzögerungsleitung diente als Referenz. Erste Messungen an Filterfolien und gelähnlichen Agarphantomen, die die optischen Eigenschaften von menschlichem Gewebe nachbildeten, lieferten eine räumliche Auflösung von mindestens 36um. Durch die modulare Bauweise ist das System leicht für zweidimensionale Aufnahmen erweiterbar.</p>

This doctoral thesis summarizes research in quantum cryptography done at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology (NTNU) from 1998 through 2007. The opening parts contain a brief introduction into quantum cryptography as well as an overview of all existing single photon detection techniques for visible and near infrared light. Then, our implementation of a fiber optic quantum key distribution (QKD) system is described. We employ a one-way phase coding scheme with a 1310 nm attenuated laser source and a polarization-maintaining Mach-Zehnder interferometer. A feature of our scheme is that it tracks phase drift in the interferometer at the single photon level instead of employing hardware phase control measures. An optimal phase tracking algorithm has been developed, implemented and tested. Phase tracking accuracy of +-10 degrees is achieved when approximately 200 photon counts are collected in each cycle of adjustment. Another feature of our QKD system is that it uses a single photon detector based on a germanium avalanche photodiode gated at 20 MHz. To make possible this relatively high gating rate, we have developed, implemented and tested an afterpulse blocking technique, when a number of gating pulses is blocked after each registered avalanche. This technique allows to increase the key generation rate nearly proportionally to the increase of the gating rate. QKD has been demonstrated in the laboratory setting with only a very limited success: by the time of the thesis completion we had malfunctioning components in the setup, and the quantum bit error rate remained unstable with its lowest registered value of about 4%. More than half of the thesis is devoted to various security aspects of QKD. We have studied several attacks that exploit component imperfections and loopholes in optical schemes. In a large pulse attack, settings of modulators inside Alice's and Bob's setups are read out by external interrogating light pulses, without interacting with quantum states and without raising security alarms. An external measurement of phase shift at Alice's phase modulator in our setup has been demonstrated experimentally. In a faked states attack, Eve intercepts Alice's qubits and then utilizes various optical imperfections in Bob's scheme to construct and resend light pulses in such a way that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Construction of such faked states using several different imperfections is discussed. Also, we sketch a practical workflow of breaking into a running quantum cryptolink for the two abovementioned classes of attacks. A special attention is paid to a common imperfection when sensitivity of Bob's two detectors relative to one another can be controlled by Eve via an external parameter, for example via the timing of the incoming pulse. This imperfection is illustrated by measurements on two different single photon detectors. Quantitative results for a faked states attack on the Bennett-Brassard 1984 (BB84) and the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols using this imperfection are obtained. It is shown how faked states can in principle be constructed for quantum cryptosystems that use a phase-time encoding, the differential phase shift keying (DPSK) and the Ekert protocols. Furthermore we have attempted to integrate this imperfection of detectors into the general security proof for the BB84 protocol. For all attacks, their applicability to and implications for various known QKD schemes are considered, and countermeasures against the attacks are proposed. The thesis incorporates published papers [J. Mod. Opt. 48, 2023 (2001)], [Appl. Opt. 43, 4385 (2004)], [J. Mod. Opt. 52, 691 (2005)], [Phys. Rev. A 74, 022313 (2006)], and [quant-ph/0702262].

Laser Doppler Vibrometry (LDV) is a non-contact technique for sensing surface vibrations. Traditionally, LDV uses one or more fixed beams to measure the vibrational velocity of specific points and orientations. In order to measure an angular velocity at least two laser beams are required. Instead, this research proposes to develop a Continuous Scanning Laser Doppler Vibrometer (CSLDV) technique, based on a single laser beam continuously sweeping the area of interest using a scanning mirror. Linear scans allow the measurement of normal and angular velocity while circular scans allow the measurement of normal velocity and two angular velocities. The first part of the study analyzes the performance of rigid body models of both the short line and circular scans (< 1 cm) for measuring low broadband frequency vibrations of gel samples. This thesis focused on low frequency broadband vibration since natural human body vibrations (such as tremor or breathing) are typically below a few hundred hertz. Results for normal and angular velocity measurements are validated against conventional method of using two fixed LDVs. The second part of this research investigates the CSLDV technique for longer scans (< 5 cm). These long scans will be used to act as an array of virtual transducers at multiple points along the scanning path of the single laser beam; thus yielding similar information obtained using an array of several real fixed LDVs. A practical challenge encountered when using CSLDV is speckle noise, that is generated when a coherent light source is reflected back from an optically rough surface. The effect of speckle noise will be quantified by varying different parameters such as scan lengths, scanning frequency, target to sensor distance and the amplitude of excitation. These parameters will be optimized in order to reduce the error of vibration measurements obtained from the CSLDV. Such systems will be used to monitor multiple degrees of freedom of human skeletal muscle vibrations for elastography purposes. The forced vibration of human muscles will be analyzed using these CSLDV techniques. Overall contributions of this work include: (1) Validation of rigid body models of both short line and circular scans CSLDV for broadband low frequency linear and angular velocity measurements; (2) application to sensing natural human body vibrations (e.g., hand tremors); (3) replacement of an array of vibration sensors by a single long line scan CSLDV. (4) development of a dynamic elastography technique for skeletal muscles using CSLDV.