Study of the Errors in Interpolated Fast Fourier Transform for Interferometric Applications

Frequency estimation is often the basis of various measurement techniques, among which optical distance measurement stands out. One of the most used techniques is interpolated fast Fourier transform due to its simplicity, combined with good performance. In this work, we study the lim-its of this technique in the case of real signals, with reference to a particular interferometric tech-nique known as self-mixing interferometry. The aim of this research is the better understanding of frequency estimation performances in real applications, together with guidance on how to im-prove them in specific optical measurement techniques. An optical rangefinder, based on self-mixing interferometry, has been realized and characterized. The simulation results allow us to explain the limits of the interpolated fast Fourier transform applied to the realized instrument. Fi-nally, a method for overcoming them is proposed by decorrelating the errors between the meas-urements, which can provide a guideline for the design of frequency-modulated interferometric distance meters

Research and Application of Measurement System Base on Laser Self-Mixing Interference

激光自混合干涉效应是指由于外部物体反射或者散射，而导致光反馈回激光腔内引起光功率波动的现象。该技术不仅保证了传统干涉的测量精度，还具备单光路、结构紧凑、易准直等优点，解决了传统干涉中存在的问题，因此受到了研究人员的关注，被广泛应用于速度、位移和振动、生物医学等领域的测量。 本文介绍了激光自混合干涉效应的发展历程和研究现状。通过三种不同的数学模型，详细阐述了自混合效应的机理，并对自混合干涉系统进行数值仿真，进而分析研究了系统模型中各参数对自混合干涉信号的影响。在此基础上，搭建半导体激光器自混合干涉测量系统，通过观察和研究实验现象，验证了理论仿真的结果。此外，本文还根据自混合基本数学模型，研究了...As a new laser technique called, self-mixing interference (SMI), which is based on the interaction of cavity field with the field backscatter from the remote target, has increasingly garnered intense attention. The SMI has advantages of simple and compact system structure and easy collimated light path. Therefore, the applications of the SMI have been popularized in many fields, including metrolog...学位：工学硕士院系专业：信息科学与技术学院_光学工程学号：2312013115309

A compact dual atom interferometer gyroscope based on laser-cooled rubidium

We present a compact and transportable inertial sensor for precision sensing of rotations and accelerations. The sensor consists of a dual Mach-Zehnder-type atom interferometer operated with laser-cooled $^{87}$Rb. Raman processes are employed to coherently manipulate the matter waves. We describe and characterize the experimental apparatus. A method for passing from a compact geometry to an extended interferometer with three independent atom-light interaction zones is proposed and investigated. The extended geometry will enhance the sensitivity by more than two orders of magnitude which is necessary to achieve sensitivities better than $10^{-8}$rad/s/$\sqrt{\rm Hz}$.Comment: 9 pages, 8 figure

Self-Mixing Laser Distance-Sensor Enhanced by Multiple Modulation Waveforms

Optical rangefinders based on Self-Mixing Interferometry are widely described in literature, but not yet on the market as commercial instruments. The main reason is that it is relatively easy to propose new elaboration techniques and get results in controlled conditions, while it is very difficult to develop a reliable instrument. In this paper, we propose a laser distance sensor with improved reliability, realized through a wavelength modulation at a different frequency, able to decorrelate single measurement errors and obtain improvement by averages. A dedicated software is implemented to automatically calculate the modulation pre-emphasis, needed to linearize the wavelength modulation. Finally, data selection algorithms allow to overcome signal fading problems due to the speckle effect. A prototype demonstrates the approach with about 0.1 mm accuracy up to 2 m of distance at 200 measurements per second

Implementation of a high resolution optical feedback interferometer for microfluidics applications

Recent progress of interferometric sensors based on the optical feedback in a laser diode have demonstrated possibility for measurement of flow rates and flow-profiles at the micro-scale. That type of compact and embedded sensors is very promising for a research and industrial field –microfluidics – that is a growing domain of activities, at the frontiers of the physics, the chemical science, the biology and the biomedical. However, the acquisition of flow rate or local velocity at high resolution remains a very challenging issue, and the sensors that have been proposed so far did not have been giving sufficient information on the nature of the particles flowing. The present thesis is driven to the implementation, validation and evaluation of the sensing performances of the optical feedback interferometry technology in both chemical and biomedical fields of applications. The elaboration of a new generation of sensors that will provide both a high spatial resolution for 2D Doppler imaging is presented, as well as a methodology that gives further information on the flowing particles concentration and/or dimensions. Then, a new embedded optical feedback interferometry imager for flowmetry has been realized using a 2-axis beamsteering mirror mounted on Micro-Electro-Mechanical Systems (MEMS) thus taking the full advantage of the compactness offered by the optical feedback interferometry sensing scheme. While previous works on optical feedback interferometry flowmetry have been limited to high particle densities fluids in single or multiple scattering regimes, we present also a sensing technique based on the optical feedback interferometry scheme in a laser diode that enables single particle detection at micro and nanoscales through the Doppler-Fizeau effect. Thanks to the proposed signal processing, this sensing technique can detect the presence of single spherical polystyrene micro/nanospheres seeded in watery suspensions, and measure their flow velocity, even when their diameter is below half the laser wavelength. It discriminates particle by their diameter up to a ratio of 5 between large and small ones while most of the technologies for particle characterization is bulk and requires manipulation of the fluid with small volume handling, precise flow and concentration control. Altogether, the results presented in this thesis realize a major improvement for the use of optical feedback interferometry in the chemical engineering or biomedical applications involving micro-scale flows

Developing a laser-based biosensor with plasmonic accuracy

This work evaluates a newly developed laser-based sensor which detects small changes of the refractive index. Currently, the state of the art in high-accuracy refractive index sensing is plasmonic biosensors (SPR). However, the high cost, the complexity and the sensitivity of the plasmonics set-up has not allowed yet being part of the market. On the other hand, the technique proposed in this project, based on Differential Self Mixing Interferometry (DSMI), counts some low-cost, stability and compactness advantages. Theoretical models, which have been studied and simulated along this research, are presented showing that the technique is capable to measure refractive index with an accuracy of 10-7. Two experimental set-ups for validation have been built along this thesis, and a series of experimental tests were performed. Results showed good agreement between theory and experiment with a reasonable reduction in performance due to instability issues. The first experimental set-up showed an accuracy of 10-5 in refractive index-sensing and the final set-up showed a resolution of 0.25g/l in detection of glucose concentration in water while it is capable to improve its accuracy with some small modification.Este trabajo evalúa un sensor basado en láser de nuevo desarrollo, con la capacidad de detectar pequeños cambios de índice de refracción. Actualmente, el estado de la técnica en alta precisión de detección de índice de refracción es el uso de sensores plasmónicos (SPR). Sin embargo, el alto costo, la complejidad y la sensibilidad de la puesta a punto de los sistemas basados en SPR no ha permitido aún su entrada en el mercado. Por otro lado, la técnica propuesta en este proyecto, basada en interferometría diferencial de autorrecombinación (DSMI), cuenta con ventajas de coste, estabilidad y compacidad respecto a los sensores SPR, de amplio uso en aplicaciones biológicas. Diferentes modelos teóricos y simulaciones desarrollados a lo largo de esta investigación se describen en detalle, mostrando que la técnica es capaz de medir el índice de refracción con una exactitud cercana a 10-7. Se han construido dos montajes experimentales para la validación del principio de medida a lo largo de esta Tesis, y se han realizado una serie de pruebas experimentales que han permitido analizar en detalle las limitaciones debidas a las condiciones de contorno. Los resultados muestran una buena concordancia entre teoría y experimento, con una reducción en el rendimiento teórico debido sobre todo a problemas de inestabilidad y de condiciones experimentales. El primer montaje experimental mostró una precisión de 10-5 en la medida del índice de refracción, y en el dispositivo final se mostró una resolución de 0.25 g/L en la detección de la concentración de glucosa en agua, con posibilidades de modificar su precisión con pequeñas modificaciones en el montaje.Aquest treball avalua un sensor basat en làser de nou desenvolupament, amb la capacitat de detectar petits canvis d'índex de refracció. Actualment, l'estat de la tècnica en alta precisió de detecció d'índex de refracció és l'ús de sensors plasmònics (SPR). No obstant això, l'alt cost, la complexitat i la sensibilitat de la posada a punt dels sistemes basats en SPR no ha permès encara la seva entrada al mercat. D'altra banda, la tècnica proposada en aquest projecte, basada en interferometria diferencial de autorrecombinació (DSMI), compta amb avantatges de cost, estabilitat i compacitat respecte als sensors SPR, d'ampli ús en aplicacions biològiques. Diferents models teòrics i simulacions desenvolupats al llarg d'aquesta investigació es descriuen en detall, mostrant que la tècnica és capaç de mesurar l'índex de refracció amb una exactitud propera a 10-7. S'han construït dos muntatges experimentals per a la validació del principi de mesura al llarg d'aquesta Tesi, i s'han realitzat una sèrie de proves experimentals que han permès analitzar en detall les limitacions degudes a les condicions de contorn. Els resultats mostren una bona concordança entre teoria i experiment, amb una reducció en el rendiment teòric a causa sobretot de problemes d'inestabilitat i de condicions experimentals. El primer muntatge experimental va mostrar una precisió de 10-5 en la mesura de l'índex de refracció, i en el dispositiu final es va mostrar una resolució de 0.25 g / L en la detecció de la concentració de glucosa en aigua, amb possibilitats de modificar la seva precisió amb petites modificacions en el muntatge

Simultaneous measurement for material parameters using self-mixing interferometry

Material related parameters such as Young’s modulus and internal friction are important for mechanical and material engineering. These parameters play key roles in the material performances. It has been a great interest to measure the value of these parameters. Traditional methods including tensile test, flexure test, and others are destructive methods often cause damages to specimen and have low accuracy. In recent years, the impulse excitation technique (IET), a non-destructive technique to determine Young’s modulus and internal friction of the material has attracted great attention. The detection system used for IET is normally microphone, accelerometer and so on. Selfmixing interferometry (SMI), an emerging sensing technique, which is non-destructive, non-contact, compact structure, and low-cost has been developed for high accuracy sensing applications, such as displacement, velocity and distance measurement and so on is suitable for the material related parameters measurement. A normal SMI system consists of a laser diode (LD) and a target to form the external cavity of the LD. When a portion of the light is reflected or backscattered to the laser cavity, leading to a modulated laser power of LD. This modulated laser power is referred as SMI signal, which carries the information of vibration of the target. In this thesis, a measurement method combining IET with SMI for material related parameters measurement is proposed. By applying wavelet transform onto the SMI signal, both resonant frequency and damping factor of the specimen vibration can be retrieved at the same time. Therefore, both Young’s modulus and internal friction of the specimen can be calculated simultaneously. The optical fibre is introduced to the system. With the installation of the optical fibre, the flexibility of the measurement is greatly improved. The measurement results show the feasibility for simultaneous measurement of material related parameters. A graphical user interface is designed to improve the user experience for the measurement

FLEA: Fresnel-limited extraction algorithm applied to spectral phase interferometry for direct field reconstruction (SPIDER)

We present a novel extraction algorithm for spectral phase interferometry for direct field reconstruction (SPIDER) for the so-called X-SPIDER configuration. Our approach largely extends the measurable time windows of pulses without requiring any modification to the experimental X-SPIDER set-up.Comment: 24 pages 26 references 8 figure