Dissertations / Theses on the topic 'Diode laser sensor'

Spatially-resolved measurements of flame temperature have been demonstrated with diode lasers for the first time. The technique is based on the use of blue diode lasers to perform laser-induced fluorescence on indium atoms seeded to the flame. Temperature measurements have been carried out in laminar flames both by the two-line atomic fluorescence technique, and also by a novel line-shape thermometry method that requires the use of only a single diode laser. The first part of this work involved the development of blue extended cavity diode lasers with favourable tuning properties. Two custom-designed extended cavity diode lasers (ECDL) have been built, emitting at wavelengths of around 410 nm and 451 nm respectively. These devices are capable of mode-hop free tuning over ranges greater than 90 GHz. The performance of these devices exceeds that of commercially available systems and a patent application has been filed. High resolution fluorescence spectroscopy has been performed on both the 52P1/2→62S1/2 and 52P3/2→62S1/2 transitions of indium atoms seeded at trace quantities into atmospheric pressure flames. In both cases, the spectra obtained show excellent agreement with a theoretical fit based on the individual hyperfine components of the transition. The two ECDLs have been used to build a sensor for the measurement of temperature in combustion systems. It is much simpler, more compact, less expensive, and more versatile than any previously existing device. The two lasers were used sequentially to probe indium atoms seeded to the flame. The ratio of the resulting fluorescence signals is related to the relative populations in the two sub-levels of the spin-orbit split ground state of indium, and thus to the temperature. Temperature measurements have been successfully performed in a laminar flame and the data thus obtained do not need to be corrected by any ‘calibration constant’. This novel thermometry technique offers a robust alternative to traditional methods involving bulky high power lasers. A further development has been made by demonstrating a fluorescence line-shape thermometry technique requiring only a single diode laser excitation source. Progress has been made towards the goal of rapid temperature measurements appropriate to the study of turbulent flames. This involved the development of a simple technique for actively locking the wavelength of the blue diode laser to a resonance line of the tellurium molecule. A high-speed thermometry system would work by rapidly switching between the two locked laser beams using an optical modulator.

The diploma thesis deals with design of the converter card for the precise control of a laser diode. At first, there are described the principles of the laser diode, photodiode and basic functions of optical fiber sensors. Following chapter deals with description of developed converter card. In the diploma thesis are discussed all function blocks of the converter card and they are explained in detail. In the thesis are subsequently tested all problem parts of the converter card for the precise control of the laser diode, such as fast switching of the current flowing through the laser diode and design of the connection for evaluating of current pulse from the sensing photodiode. An integral part of thesis is a description of created printed circuit board and there are described all used layers and devices’ layout on the PCB. Final part of the diploma thesis deals with firmware for the microcontroller, which was made for testing of all function blocks of the converter card for the precise control of a laser diode. At the same time was developed software for PC, which communicates with the converter card via universal serial bus (USB).

Hypersonic vehicles, based on scramjet engines, have the potential to deliver inexpensive access to space when compared with rocket propulsion. The technology, however, is in its infancy and there is still much to be learned from fundamental studies.¶ Flows that represent the conditions inside a scramjet engine can be generated in ground tests using a free-piston shock tunnel and a combustor model. These facilities provide a convenient location for fundamental studies and principles learned during ground tests can be applied to the design of a full-scale vehicle.¶ A wide range of diagnostics have been used for studying scramjet flows, including surface measurements and optical visualisation techniques.¶ The aim of this work is to test the effectiveness of tunable diode laser absorption spectroscopy (TDLAS) as a scramjet diagnostic.¶ TDLAS utilises the spectrally narrow emission from a diode laser to probe individual absorption lines of a target species. By varying the diode laser injection current, the laser emission wavelength can be scanned to rapidly obtain a profile of the spectral line. TDLAS has been used previously for gas-dynamic sensing applications and, in the configuration used in this work, is sensitive to temperature and water vapour concentration.¶ The design of the sensor was guided by previous work. It incorporated aspects of designs that were considered to be well suited to the present application. Aspects of the design which were guided by the literature included the laser emission wavelength, the use of fibre optics and the detector used. The laser emission wavelength was near 1390 nm to coincide with relatively strong water vapour transitions. This wavelength allowed the use of telecommunications optical fibre and components for light delivery. Detection used a dual-beam, noise cancelling detector.¶ The sensor was validated before deployment in a low-pressure test cell and a hydrogen–air flame. Temperature and water concentration measurements were verified to within 5% up to 1550 K. Verification accuracy was limited by non-uniformity along the beam path during flame measurements.¶ Measurements were made in a scramjet combustor operating in a flow generated by the T3 shock tunnel at the Australian National University. Within the scramjet combustor, hydrogen was injected into a flame-holding cavity and the sensor was operated downstream in the expanded, supersonic, post-combustion flow. The sensor was operated at a maximum repetition rate of 20 kHz and could resolve variation in temperature and water concentration over the 3ms running time of the facility.¶ Results were repeatable and the measurement uncertainty was smaller than the turbulent fluctuations in the flow. The scramjet was operated at two fuel-lean equivalence ratios and the sensor was able to show differences between the two operating conditions. In addition, vertical traversal of the sensor revealed variation in flow conditions across the scramjet duct.¶ The effectiveness of the diagnostic was tested by comparing results with those from other measurement techniques, in particular pressure and OH fluorescence measurements, as well as comparison with computational simulation.¶ Combustion was noted at both of the tested operating conditions in data from all three measurement techniques.¶ Computation simulation of the scramjet flow significantly under-predicted the water vapour concentration. The discrepancy between experiments and simulation was not apparent in either the pressure measurements or the OH fluorescence, but was clear in the diode laser results.¶ The diode laser sensor, therefore, was able to produce quantitative results which were useful for comparison with a CFD model of the scramjet and were complimentary to information provided by other diagnostics.

L'interférométrie à rétro-injection optique, également connu sous le nom de Self-Mixing, permet de concevoir des capteurs qui sont compacts, auto-alignés et sans contact. Dans ce phénomène, une partie du faisceau laser de retour réfléchi par la cible rentre dans la cavité active de laser et fait varier ses propriétés spectrales. La diode laser agit alors comme une source de lumière, un microinterféromètre ainsi qu'un détecteur de lumière. Dans cette thèse, un capteur de déplacement, basé sur la rétro-injection optique, a été optimisé de sorte que des mesures précises peuvent être obtenues en temps réel. Le capteur est robuste à la disparition des franges de self-mixing pour des vibrations harmoniques. Il est également capable de s'adapter à un changement dans le régime de feedback optique et peut donc extraire le déplacement dans les cas les plus répandus expérimentalement, à savoir un feedback faible puis modéré. L'utilisation de l'optique adaptative, sous la forme d'une lentille liquide, a également été démontrée pour ce capteur, ce qui nous a permis de maintenir le capteur dans un régime de feedback favorable. L'influence du speckle a également été réduite de telle sorte que le capteur mesure jusqu'à la gamme centimétrique pour des cibles non- oopératives. Une nouvelle technique est également présentée, elle permet de rendre le capteur insensible aux vibrations mécaniques parasites qui fausseraient la mesure pour des conditions industrielles
Optical Feedback Interferometry, also known as Self-Mixing, results in compact, selfaligned and contact-less sensors. In this phenomenon, a portion of the laser beam is back reflected from the target and enters the active laser cavity to vary its spectral properties. The laser diode then simultaneously acts as a light source, a micro- nterferometer as well as a light detector. In this thesis, a self-mixing displacement sensor has been optimised so that precise measurement can be obtained in real-time. The sensor is robust to the disappearance of self-mixing fringes for harmonic vibrations. It is also able to auto-adapt itself to a change in the optical feedback regime and so can extract displacement from the weak as well as moderate feedback regime signals. The use of adaptive optics, in the form of a liquid lens, has also been demonstrated for this sensor, which has allowed us to maintain the sensor in a fringe-loss less regime. The influence of speckle has also been reduced so that the sensor can now measure up to the centimetric range for non-cooperative targets. A novel technique has also been presented that makes the sensor insensitive to parasitic mechanical vibrations that would falsify the measurement under industrial conditions

This project is about design of contactless measuring ventilator - revolution counter. The counter serves to measurement of the speed of ventilator. The measurement is based on optical method of receiving the reflected laser beam. To measure and calculate use the revolution counter the microcontroller. This measured value is diplayed on LCD. After design follows experimental measurement.

The use of continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near-infrared (IR) region has great potential for the design of ultra-sensitive, compact, robust and cost-effective novel optical sensors capable of detecting trace species present in the atmosphere. The research work presented in this thesis focuses on the development and implementation of a fully automated, cryogen-free and compact cw-CRD spectrometer, combined with adsorbent filled dual-trap sample pre-concentration for monitoring trace C2H2 mixing ratios in ambient air.

Le phénomène d’interférométrie par réinjection optique se produit lorsqu’une portion de la puissance optique du laser est rétrodiffusée par une cible distante puis réinjectée dans la cavité laser ce qui affecte les propriétés d’émission du laser (fréquence et puissance en particulier). Ce principe résulte alors en un capteur interférométrique compact, auto-aligné et sans contact. Des applications récentes des capteurs par réinjection optique dans les domaines de la microfluidique et de l’acoustique ont montré des résultats prometteurs et ouvert de nouveaux domaines de recherche. Pourtant, dans le cadre de ces applications, l’amplitude du signal est extrêmement faible à cause de la faible amplitude des variations de la puissance rétrodiffusée qui est mesurée. Dans cette thèse, un modèle analytique décrivant la dépendance de l’amplitude du signal issu d’une diode laser monomode au courant d’injection et à la température est développé à partir des équations d’évolution de Lang et Kobayashi. Le modèle a été développé pour toutes les méthodes connues d’acquisition du signal interférométrique par réinjection optique : par la photodiode de monitoring incluse dans le boîtier de la diode laser, par la captation de la puissance optique au moyen d’un photodétecteur externe et par l’amplification de la tension aux bornes de la diode laser elle-même. Le modèle démontre que les signaux des photodiodes et de la tension sont liés à l’efficacité externe de la diode laser, qui elle-même est fonction du courant injecté et de la température. Qui plus est, le modèle prédit une évolution très différente de l’amplitude de ces différents signaux en fonction du courant d’injection ou de la température. Un résultat remarquable, confirmé par une campagne de mesures pour ces trois types de signaux sur une large plage de courants d’injection et de températures. Ainsi ce modèle simple permet une compréhension nouvelle des stratégies de polarisation très différentes de la diode laser permettant d’obtenir une sensibilité optimale du capteur dans les différents schémas d’acquisition du signal. Par ailleurs, les relations entre la phase et l’amplitude des signaux issus des photodiodes externes et de monitoring ont été étudiées sur le plan théorique et expérimental ce qui a permis de révéler des résultats inattendus. À partir du modèle et basé sur des observations expérimentales, une étude critique a été menée sur l’impact de la combinaison des trois signaux dans la stratégie de traitement du signal afin d’améliorer la sensibilité du capteur aux réinjections optiques de faible amplitude
The optical feedback interferometry phenomenon occurs when a portion of the output optical power is back-scattered from a remote target and coupled into the laser cavity to vary the laser’s emission properties (frequency and power mostly). Thus, this scheme results in a compact, self-aligned and contact-less interferometric sensor. Recent applications of optical feedback interferometer in the domains of microfluidics or acoustics have shown promising results and open new fields of researches. However in these applications, the amplitude of the sensing signal is extremely small due to the weakness of the backscattered power changes that are measured. In this thesis, an analytical model that describes the laser injection current and temperature dependence of the optical feedback interferometry signal strength for a single-mode laser diode has been derived from the Lang and Kobayashi rate equations. The model has been developed for all the known signal acquisition methods of the optical feedback interferometry scheme: from the package included monitoring photodiode, by collection of the laser power with an external photodetector and by amplification of the variations in the laser junction voltage. The model shows that both the photodiodes and the voltage signals strengths are related to the laser slope efficiency, which itself is a function of the laser injection current and of the temperature. Moreover, the model predicts different behaviors of the photodiodes and the voltage signal strengths with the change of the laser injection current and the temperature; an important result that has been proven by conducting measurements on all three signals for a wide range of injection current and temperature. Therefore, this simple model provides important insights into the radically different biasing strategies required to achieve optimal sensor sensitivity for the different interferometric signal acquisition schemes. In addition, the phase and amplitude relationships between the external and the in-package photodiode signals have been investigated theoretically and experimentally demonstrating unexpected results. Based on our model and on experimental observations, a critical study has been performed on the impact of the combination of the three signals in the signal processing strategy in order to improve the sensor sensibility to low amplitude optical feedback

An all-solid-state continuous-wave (cw) laser system for mid-infrared absorption measurements of the carbon monoxide (CO) molecule has been developed and demonstrated. The single-mode, tunable output of an external-cavity diode laser (ECDL) is difference-frequency mixed (DFM) with the output of a 550-mW diode-pumped cw Nd:YAG laser in a periodically-poled lithium niobate (PPLN) crystal to produce tunable cw radiation in the mid-infrared. The wavelength of the 860-nm ECDL can be coarse tuned between 860.78 to 872.82 nm allowing the sensor to be operated in the 4.4 – 4.8 µm region. Results from single-pass mid-IR direct absorption experiments for CO concentration measurements are discussed. CO measurements were performed in CO/CO2/N2 mixtures in a room temperature gas cell that allowed the evaluation of the sensor operation and data reduction procedures. Field testing was performed at two locations: in the exhaust of a well-stirred reactor (WSR) at Wright-Patterson Air Force Base and the exhaust of a gas turbine at Honeywell Engines and Systems. Field tests demonstrated the feasibility of the sensor for operation in harsh combustion environments but much improvement in the sensor design and operation was required. Experiments in near-adiabatic hydrogen/air CO2-doped flames were performed featuring two-line thermometry in the 4.8 µm spectral region. The sensor concentration measurement uncertainty was estimated at 2% for gas cell testing. CO concentration measurements agreed within 15% of conventional extractive sampling at WSR, and for the flame experiments the repeatability of the peak absorption gives a system uncertainty of 10%. The noise equivalent CO detection limit for these experiments was estimated at 2 ppm per meter, for combustion gas at 1000 K assuming a SNR ratio of 1.

Les nouveaux capteurs d’image 3D sont des éléments clés pour exploiter pleinement les applications émergentes dans les domaines de l'imagerie 3D et de la vision par ordinateur telles que la reconnaissance faciale, la capture de mouvement, la détection de présence ou encore la réalité augmentée. Ces capteurs reposent essentiellement sur une technique de mesure de distance. Parmi celles-ci, la mesure indirecte du temps de vol des photons présente l’avantage d’une mise en œuvre simple, fiable et économique appropriée aux applications mobiles grâce au fonctionnement conjugué d’un capteur d’image et d’une diode laser. Le principe consiste à calculer une distance en mesurant le déphasage entre un signal laser infrarouge modulé et le signal optique renvoyé après réflexion sur un objet de la scène. Des impulsions laser avec un rapport cyclique proche de 50\% sont généralement utilisées comme signal laser en modulant le courant à travers une diode laser. Le travail de thèse se focalise sur l'étude et la conception d'un circuit intégré de pilotage de diode laser qui soit à la fois compact, efficace et peu cher, pour des applications d'imagerie 3D utilisées dans les téléphones portables. La nouveauté ici concerne l'intégration du pilote entier (hormis la diode laser et quelques composants passifs) sur une seule puce tout en respectant les contraintes des applications mobiles (faibles tensions d'alimentation, forte intégration). Un autre défi important concerne les pics de tension se produisant pendant les transitoires rapides dus aux inductances parasites. Enfin, un fort rendement électrique s’avère indispensable dans le but de prolonger l’autonomie de la batterie et minimiser l’auto-échauffement. A des fins de comparaison, deux topologies de pilotage différentes, mettant en oeuvre un convertisseur DC/DC associé à un élément de commutation connecté soit en série soit en parallèle de la diode laser, ont été retenues comme base pour concevoir le pilote de diode laser. Deux prototypes ont été réalisés en utilisant une technologie CMOS 130nm de STMicroelectronics, qui sont capables de fournir des impulsions de courant jusqu'à 3A avec une largeur d'impulsion de 2,5ns à une fréquence maximale de 200MHz sous une tension d'alimentation de 3,6V. Dans ces conditions, ils délivrent une puissance électrique de sortie moyenne de 4,5W à la diode laser avec un rendement électrique d'environ 60%
Three-dimensional (3D) image sensors are key enablers for unlocking emerging applications in consumer electronics such as facial recognition, presence detection, gesture control or Augmented Reality (AR). These sensors mostly rely on range measuring techniques such as structured-light or Time-of-Flight (ToF) principles. The indirect Time-of-Flight (iToF) principle offers the advantage of a simple, reliable and low cost solution for mobile applications by using a laser transmitter and an image sensor. Its operating principle is to calculate a distance by measuring the phase shift between a modulated infrared laser signal and the optical signal received by the sensor after reflection on an object from the scene. Laser pulses with a duty cycle close to 50\% are usually sent through the scene by modulating the current through a semiconductor laser diode. The thesis is focused on the study and design of a compact, cost-effective and efficient integrated Laser Diode Driver (LDD) for 3D-depth sensing applications used in mobile phones. The novelty here concerns the integration of the whole driver (except laser diode and some passive components) on a single chip while accommodating mobile phone constraints (low supply voltages, high integration). Another important requirement concerns the high voltage spikes occurring during fast transients due to stray inductance. Finally, a high efficiency and low losses in the chip are critical for saving the battery lifetime and minimizing the self-heating. For comparison purposes, two different driving topologies, implementing a DC/DC converter connecting a switching element either in series or in parallel with a laser diode, have been retained as basis for designing the laser diode driver. Two IC prototypes have been realized using a 130nm CMOS technology from STMicroelectronics. Both drivers are able to generate current pulses up to 3A with a 2.5ns pulse width at a maximum 200MHz frequency under a 3.6V supply voltage. Under theses conditions, they provide an average output electrical power of 4.5W to the laser diode with an electrical efficiency of around 60%

A Laser Music System has been created, that combines a laser and light sensor system with an infrared distance sensing system that detects the position of a user’s hand when it intersects one or more of the individual laser beam. The laser beams, which are made visible by a small amount of smoke in a dark room, provide visual guidance to the user to reduce the difficulty of using a non-contact instrument as well as enhancing an appealing optical effect for the user. The system uses a number of Sharp distance sensors to map the position of the user’s hand to a variable like pitch. The user should move their hand to different heights to achieve a desired pitch. The laser beam should be broken to trigger the desired note.

An improved version of an automated near infra-red continuous wave cavity ring down spectrometer with sample preconcentration has been developed, for the detection of trace gases in the atmosphere and isotopologue ratio analysis. Three different lasers operating at wavelengths in the range 1.5-1.6 urn have been used for the experiments in conjunction with three different pre-concentration systems. The instrument has been used for three separate studies: continuous measurement of ethene (C2H4) in Bristol air; detection of nitrous oxide (N20) in ambient air; and acetylene isotopologue ratio (13CH4/12CH4) analysis in cigarette smoke samples. Mixing ratios of ethene have been observed to vary from 0.6 ppbv to 1.2 ppbv in Bristol air with a strong influence of the prevailing wind direction. Winds from the west and the north were observed to decrease and increase the ethene mixing ratio in Bristol air respectively. The observed variations have been discussed with consideration of probable sources and sinks and different meteorological parameters. Nitrous oxide in Bristol air has been observed to have a mixing ratio of ~320 ppb; consistent with global abundance of this long-lived greenhouse gas. Acetylene isotopologue ratios have been measured in smoke samples from two different brands of cigarette chosen as a test source of C2H2 from combustion of plant material. The average s\3e value of the five consecutive determinations for each cigarette brand was found to be -11.86 ± 0.55 %0 (Marlboro) and -4.98± 0.39 %0 (Lambert & Butler). The observed isotopologue ratios match closely with similar measurement of different samples derived from biomass burning conducted in different laboratories and analysed using isotopologue ratio mass spectrometry (IRMS). An improved version of a mid infra-red cavity enhanced absorption spectroscopy (CEAS) apparatus has been developed for isotopologue ratio analysis in gas samples. A difference frequency generation (DFG) based laser system was used as source of mid-IR radiation and a lock-in amplifier was used to demodulate the signal from sources of noise. The spectrometer has been used successfully to conduct methane isotopologue ratio analysis (13CH4/12CH4) in a 5% methane mixture in argon and carbon dioxide (COL) buffer gas. An average isotopologue ratio value of -47.3 ± 2.3 %0 has been observed which matches closely with two separate measurements on this standard sample, one using IRMS and another using a commercial near IR cavity ring down spectrometer.

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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

This diploma thesis deals with the influence of long fiber optic paths on the polarization state of light and their use for powering polarization sensors. The aim of the diploma thesis was to design the arrangement of optical fiber components so that the polarization properties of light at the end of the path are further usable for sensory purposes. Four partial measurements with a long path (in a laboratory setting, laying in the ground, on a curtain, under the influence of external influence) and one measurement without a path under the influence of external influence were designed. The overall measurement results demonstrate that for the functional power supply of long-distance sensor systems, an existing single-mode fiber can be used (laid by laying in the ground), into which a light source for a given sensor system would be multiplexed. In the discussion, all types of measurements are analyzed and compared with each other. Finally, the overall result is summarized and applications are described in which such a sensor system could be used.

Interferometric optical fiber sensors have proved many orders of magnitude more sensitive than their electrical counterparts, but they suffer from limitations in signal demodulation caused by phase ambiguity and complex fringe counting when the output phase difference exceeds one fringe period. Various signal demodulation methods have been developed to overcome some of the these drawbacks with limited success. This thesis proposes a new measurement system for the extrinsic Fabry-Perot interferometer (EFPI) sensor. Using a wavelength modulated source and a novel extended-gap EFPI, some of the limitations of interferometric signal demodulation are overcome. By scanning the output wavelength of a multilongitudinal mode laser diode through current modulation, the EFPI sensor signal is scanned through multiple fringes. Gap movement is then unambiguously determined by monitoring the phase of the multiple fringe pattern.
Master of Science

Cette thèse de doctorat a été réalisée au sein du III-VLab, en partenariat avec l’Institut d’Electronique du Sud (IES). L’objectif de ce travail de thèse vise d’une part à l’optimisation des performances des diodes laser DFB émettant à 780 nm et le développement d’une source plus compacte (MOPA) à 780nm, intégrant de façon monolithique l’oscillateur maître (laser à rétro-action répartie ou DFB) et l’amplificateur de puissance, et d’autre part, à appréhender les phénomènes de bruit, permettant d’évaluer la qualité technologique des lasers. Les développements autour de la longueur d’onde 780 nm, se sont organisés en plusieurs thématiques : les lasers Fabry-Perot et DFB, les amplificateurs (SOA), les MOPA et l’étude du bruit des lasers. Nous avons étudié des structures de différentes épaisseurs de puits quantiques (160Å, 135 Å et 145 Å). La comparaison des performances globales des différentes structures de lasers larges, loin d’être évidente, nous a permis de choisir celle intégrant un puits quantique de 160 Å, pour la réalisation des lasers Fabry-Perot à ruban étroit (3µm à 4µm). Nous avons obtenu sur des lasers larges, de 3 mm de long, bruts de clivage, une puissance d’environ 5 watts par face pour un courant d’injection continu autour de 10 A. Les simulations et caractérisations électro-optiques menées sur des lasers ridge Fabry-Perot, ont servi à affiner le dessin des DFB à 780 nm, par rapport aux briques de base existantes du III-V Lab, et à proposer des structures à cavités optiques larges et super-large (LOC et SLOC) optimisées, en termes de puissance, qualités de faisceau et spectrale.Les mesures de bruits, appuyées d’un modèle de bruit électrique, ont permis d’extraire une valeur du paramètre de Hooge de 2,1.10^-3 pour les lasers ridge, en accord avec la littérature, et qui correspond à une bonne qualité de matériau et technologique des lasers. Différents types d’amplificateurs optiques évasés ont été dessinés, réalisés et caractérisés. Les caractérisations des diverses géométries de SOA, ont donné dans l’ensemble, des valeurs de gain comprises entre 19dB et 25dB. Nous avons obtenu respectivement pour les structures d’amplificateurs à guidages entièrement par l’indice (GI), entièrement par le gain (GG) et mixte (GM), des puissances de 500mW, 750mW et 1W. L’ensemble des résultats obtenus avec ces structures sont prometteurs pour l’intégration monolithique avec le DFB. En ce qui concerne le MOPA, trois approches ont été étudiées: MOPA droit, DFB et amplificateur tiltés de 7° (par rapport à la normale aux faces clivées), et la plus prometteuse mais plus complexe, intégrant le DFB droit et l’amplificateur tilté de 7°, avec une section courbe entre les deux. La prise en compte de l’ensemble des résultats lasers Fabry-Perot, DFB et des résultats d’amplificateurs, nous ont permis de proposer des dessins MOPA originaux. Le dessin du masque réalisé, intègre toutes ces configurations de MOPA, et en plus, des SOA et DFB, qui seront utilisés comme témoins de test lors des caractérisations
This thesis has been realized in III-VLab in collaboration with the South Electronic Institute in Montpellier. The aim of this work focuses in one hand, on the performance improvement of DFB's diode lasers emitting at 780 nm, and the advanced design of a compact semiconductor laser diode (Master Oscillator Power Amplifier), integrating monolithically the master oscillator (DFB for Distributed Feedback laser); in the other hand, using the noise phenomenon’s studies as a tool, for validating of our laser technologies. The Developments round the 780 nm wavelength, have been divided into different thematic: Fabry-Perot and DFB, Semiconductor Optical Amplifiers (SOA), MOPA, and the lasers noise’s study. We have studied structures with different quantum well thickness (160Å, 135 Å and 145 Å). The comparison of global performances of broad area lasers from these different structures, far to being obvious, allowed us to choose the one that integrates the 160-Å-thickness of quantum-well, for the realization of ridge Fabry-Perot lasers of 3 to 4-µm-of width. We obtained with broad area lasers, as cleaved, with 3-mm cavity lengths, an output power around 5 watts per facet, in continuous bias current around 10 AModellings and electro-optics characterizations performed on ridge Fabry-Perot lasers, allowed to refine DFB lasers at 780 nm, in comparison of the existing building blocks in the lab; we proposed new optimized structures with Large and Super Large Optical Cavities(LOC and SLOC), in terms of optical output power, beam and spectral qualities.The noise measurements with electrical noise modelling, allowed us to extract a value of Hooge’s parameter of 2,1.10^-3, quite in agreement with literature for such lasers, which corresponds to a good material quality and laser technology.Different types of flared SOA have been designed, realized and characterized. The characterizations of various SOA geometries, have given in general, values of gain between 19 dB to 25 dB. With SOAs of types: fully Index Guiding (IG), fully Gain Guiding (GG) and Mixed Guiding (MG), we have respectively obtained 500 mW, 750 mW and 1 W. All the results obtained with these structures are promising for monolithic integration with DFB. Regarding the MOPA, three approaches have been studied. The straight MOPA, the approach of SOA and DFB with 7° tilt(relative to the normal to cleaved facets), and the most complex, but promising approach, integrating the SOA with 7° tilt, and straight DFB, with a bend section between them. By taking into account all the results obtained on Fabry-Perot lasers, DFB, and SOA results, we were able to propose original MOPA designs. The layout drawing has been realized, all the MOPA configurations and additional, DFB and SOA devices, have been included on it. They will be used as test structures for characterizations

Hypersonic vehicles, based on scramjet engines, have the potential to deliver inexpensive access to space when compared with rocket propulsion. The technology, however, is in its infancy and there is still much to be learned from fundamental studies. ¶ Flows that represent the conditions inside a scramjet engine can be generated in ground tests using a free-piston shock tunnel and a combustor model. These facilities provide a convenient location for fundamental studies and principles learned during ground tests can be applied to the design of a full-scale vehicle.¶ A wide range of diagnostics have been used for studying scramjet flows, including surface measurements and optical visualisation techniques.¶ The aim of this work is to test the effectiveness of tunable diode laser absorption spectroscopy (TDLAS) as a scramjet diagnostic.¶ ...

碩士
中正理工學院
電機工程研究所
86
ABSTRACT A chemical sensor based on surface plasmon excitation was constructed by deposited gold metal film directly on a BK-7 prism, to form a Kretschmann configuration (prism/metal film/dielectric). This chemical sensor has been optimized by use of computer simulation, the optimum thickness of depsited metal film is about 46nm. Calculated and experimentally measured performances are illustrated,compared andshowing in good agreement and experimental measurement with figures. We measured the reflectivity vs. position of the dip of surface plasmon in the optimum gold metal film with water and different concentrations of sugar solution as dielectric. We also found that the position of the surface plasmon dip with various concentrations per volume of sugar changes from 72.5 to 77.5 , and the deviation angles with water vs. various concentrations of sugar is almost linear.

碩士
國立中興大學
機械工程學系所
105
This research develop and utilize a laser diode self-mixing based three dimensional sensor, and apply to the contact probe for trigger signal measurement. The components of the three dimensional sensor system are including a laser diode, a quadrant photodiode, a beam splitter and a glass ball lens. The glass ball lens is combined with a contact probe mechanism, and placed at the straight front of the laser diode, and through measuring with the contact probe mechanism, the reflected laser light spot of the glass ball lens will cause voltage variation on the quadrant photodiode. The X and Z axis can be determined by the voltage and displacement signal trend equation from the quadrant photodiode. On the other hand, an amount of laser which is released from the laser diode reflected or scattered back from the glass ball lens will re-enter the laser cavity. The fraction of light will interfere with the original laser light inside the laser cavity, and by utilizing the property of how it react with the laser beams for the displacement signal, then the Y axis can be calculated. By combining the measuring system and the contact probe, while placing the contact probe on the machine tool to measure the standard blocks. When the contact probe reach the minimum contact displacement, the machine tool will stop immediately and records the coordinate of the machine tool, and from the coordinate of the machine tool and its relation with the measured date of the contact probe, the dimension of the standard block can be calculated. Lastly, from the confirmation of the experience for this research, indicates the high accuracy of this measuring system, with accuracy of X axis at 0.5 μm, y axis at 1.7 μm and z axis at 0.5 μm. Overall, the measurement deviation is acceptable.