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Academic literature on the topic 'Frequency stabilisation'

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Published: 4 June 2021
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Journal articles on the topic "Frequency stabilisation"

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Glance, B., P. J. Fitzgerald, K. J. Pollack, J. Stone, C. A. Burrus, G. Eisenstein, and L. W. Stulz. "Frequency stabilisation of FDM optical signals." Electronics Letters 23, no. 14 (1987): 750. http://dx.doi.org/10.1049/el:19870532.

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Fusco, V. F., and M. Gan. "Active antenna discriminator for frequency stabilisation." Electronics Letters 36, no. 4 (2000): 288. http://dx.doi.org/10.1049/el:20000322.

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Bagayev, S. N., V. S. Pivtsov, and Aleksei M. Zheltikov. "Frequency stabilisation of femtosecond frequency combs with a reference laser." Quantum Electronics 32, no. 4 (April 30, 2002): 311–14. http://dx.doi.org/10.1070/qe2002v032n04abeh002190.

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4

Smowton, P. M., B. Thomas, and R. H. Pratt. "Frequency stabilisation of visible output laser diodes." IEE Proceedings J Optoelectronics 139, no. 1 (1992): 75. http://dx.doi.org/10.1049/ip-j.1992.0014.

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Tsuchida, H., and Y. Mitsuhashi. "Frequency stabilisation of a modulated semiconductor laser." Electronics Letters 23, no. 21 (1987): 1147. http://dx.doi.org/10.1049/el:19870799.

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McNamara, P. W., H. Ward, and J. Hough. "Laser frequency stabilisation for LISA: Experimental progress." Advances in Space Research 25, no. 6 (January 2000): 1137–41. http://dx.doi.org/10.1016/s0273-1177(99)00974-6.

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REED, VALERIE C. "SUPERINTENSE FIELD IONISATION SUPPRESSION IN THE HIGH FREQUENCY REGIME." Modern Physics Letters B 06, no. 12 (May 20, 1992): 683–701. http://dx.doi.org/10.1142/s0217984992000776.

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We present a brief review of the subject of ionisation suppression, or atomic stabilisation, in intense laser fields. As a preliminary, we outline the general non-linear response of an atom to a strong laser field, describing multiphoton ionisation and harmonic generation. We then discuss methods of suppressing the ionisation rate from an atom, considering two broad regimes: strong field ionisation (I < 1016 W/cm 2), in which the suppression mechanism in generally interpreted in terms of quantum interference; and superintense field ionisation (I > 1016 W/cm 2), in which the Kramers-Henneberger frame is used to interpret why atomic stabilisation can occur.
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Desforges, F. X., Y. Andre, and P. Cerez. "High frequency stabilisation of an AlGaAs laser diode." Journal of Physics E: Scientific Instruments 19, no. 9 (September 1986): 731–33. http://dx.doi.org/10.1088/0022-3735/19/9/017.

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Nakagawa, M., T. Sato, and M. Shimba. "Frequency stabilisation of semiconductor laser using Faraday effect." Electronics Letters 25, no. 7 (1989): 430. http://dx.doi.org/10.1049/el:19890295.

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Privalov, V. E. "Prospects for frequency stabilisation of metal vapour lasers." Quantum Electronics 25, no. 3 (March 31, 1995): 286–87. http://dx.doi.org/10.1070/qe1995v025n03abeh000347.

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Dissertations / Theses on the topic "Frequency stabilisation"

1

Lepley, Jason J. "Frequency stabilisation for dense wavelength division multiplexing systems." Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310059.

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Hopper, David J. "Investigation of laser frequency stabilisation using modulation transfer spectroscopy." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16667/1/David_John_Hopper_Thesis.pdf.

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Optical frequency standards are necessary tools for accurate measurement of time and length. In practice these standards are stabilised laser systems locked to a known frequency reference. These references are typically the resonant frequencies of the atoms of an absorption medium that have been theoretically calculated to a high degree of accuracy. This thesis describes a combination of experimental and theoretical research performed on modulation transfer spectroscopy (MTS)--a technique used to frequency stabilise a laser in order to produce an accurate frequency reference--with emphasis placed on developing techniques and procedures to overcome the limitations found in existing MTS stabilised laser systems. The focus of the thesis is to generate a highly accurate frequency reference by researching the system parameters that will increase the signal to noise ratio and improve the accuracy of the reference through refinement of the signal structure. The early theoretical interpretation of MTS was effectively a low absorption approximation that occurs at low pressures. This approximation ignores the depletion of beam energy through absorption and is a distinct limitation of the theoretical model in its ability to accurately predict the influence of a range of system parameters on signal strength and structure. To overcome this limitation a 3-D (or volumetric) analysis was developed and is presented here for the first time. This volumetric model is a measure of two depleted beams interacting collinearly in an absorbing medium of iodine and is described to accurately predict the signal maximum as a function of pressure for all wavelengths. This model was found to be more accurate in predicting the influence of system parameters on the signal strength and structure, including that of pump beam intensity, pressure, saturation parameter, cell length and modulation parameters. The volumetric model is a novel approach to MTS theory but is more complex computationally than the traditional low pressure model and therefore more difficult to implement in many situations. To overcome this problem a hybrid model was developed as a combination of the low pressure and volumetric models. The comparison between the rigorous volume model and the hybrid model indicate that there is a deviation in the signal strength at high pressures. However, the agreement was very good in the pressure regimes that are commonly used to realise actual frequency references. Comparison of the hybrid model to experimental data was performed over a range of different wavelengths (532 nm, 543.5 nm, 612 nm and 633 nm) and found to be in close agreement. This gives confidence in the model to accurately predict signal strength and structure in any situation. Three mechanisms have been identified that limit the accuracy of frequency references due to the creation of residual amplitude modulation (RAM) where it shifts the frequency of the reference. The influence of RAM is included in the hybrid model as a ratio of the amplitude modulated and frequency modulated components of the saturating beam. These RAM production mechanisms result from the modulation of the saturating beam, the overlap of the beams in the medium, and the differential absorption of the sidebands in the medium. While the first mechanism has been previously reported the latter two are discussed here in detail for the first time. RAM generated by the modulators used (acousto-optic or electro-optic modulators) was typically of the order of 10% to 12%, depending on the excursion of the created sidebands. RAM generated by an asymmetric beam overlap with the modulators used was found to be as large as 30%. A combination of these two independent mechanisms can be used to provide a "RAM-free" state of the system by using one to cancel the effects of the other. The third RAM generation process--medium induced RAM--is difficult to remove but through a careful combination of absorption related parameters--namely, pump intensity, cell length, pressure and detector phase--the effects of RAM can be removed, leading to a distortion free MTS signal. Further investigation into the predictions provided by the hybrid model shows that there is a complex relationship between cell length and the optimum pressure required for maximum signal strength, such that longer cell lengths will not necessarily improve the signal strength. This is contrary to conventional thinking and is important in the MTS design process to reduce unnecessary costs and improve the signal to noise ratio and frequency accuracy. Optimisation of frequency stabilised laser systems using MTS are generally performed using trial and error. Comparison of these optimum parameter values to those predicted by the hybrid model show that for popular wavelengths such as 532 nm they are similar. In addition, the hybrid model is able to predict the frequency shifts that arise within the system parameters used and has shown that existing systems being used at 532 nm, 633 nm and 778 nm could improve their signal to noise ratio and accuracy through a variation in the parameters. A methodology based on the hybrid model is presented that can be used to calculate the optimum parameters for maximum signal strength and a "RAM-free" state for any wavelength. This systematic approach can therefore be used to guide the design of actual frequency stabilised laser systems prior to and during the design process.
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3

Hopper, David J. "Investigation of laser frequency stabilisation using modulation transfer spectroscopy." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16667/.

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Optical frequency standards are necessary tools for accurate measurement of time and length. In practice these standards are stabilised laser systems locked to a known frequency reference. These references are typically the resonant frequencies of the atoms of an absorption medium that have been theoretically calculated to a high degree of accuracy. This thesis describes a combination of experimental and theoretical research performed on modulation transfer spectroscopy (MTS)--a technique used to frequency stabilise a laser in order to produce an accurate frequency reference--with emphasis placed on developing techniques and procedures to overcome the limitations found in existing MTS stabilised laser systems. The focus of the thesis is to generate a highly accurate frequency reference by researching the system parameters that will increase the signal to noise ratio and improve the accuracy of the reference through refinement of the signal structure. The early theoretical interpretation of MTS was effectively a low absorption approximation that occurs at low pressures. This approximation ignores the depletion of beam energy through absorption and is a distinct limitation of the theoretical model in its ability to accurately predict the influence of a range of system parameters on signal strength and structure. To overcome this limitation a 3-D (or volumetric) analysis was developed and is presented here for the first time. This volumetric model is a measure of two depleted beams interacting collinearly in an absorbing medium of iodine and is described to accurately predict the signal maximum as a function of pressure for all wavelengths. This model was found to be more accurate in predicting the influence of system parameters on the signal strength and structure, including that of pump beam intensity, pressure, saturation parameter, cell length and modulation parameters. The volumetric model is a novel approach to MTS theory but is more complex computationally than the traditional low pressure model and therefore more difficult to implement in many situations. To overcome this problem a hybrid model was developed as a combination of the low pressure and volumetric models. The comparison between the rigorous volume model and the hybrid model indicate that there is a deviation in the signal strength at high pressures. However, the agreement was very good in the pressure regimes that are commonly used to realise actual frequency references. Comparison of the hybrid model to experimental data was performed over a range of different wavelengths (532 nm, 543.5 nm, 612 nm and 633 nm) and found to be in close agreement. This gives confidence in the model to accurately predict signal strength and structure in any situation. Three mechanisms have been identified that limit the accuracy of frequency references due to the creation of residual amplitude modulation (RAM) where it shifts the frequency of the reference. The influence of RAM is included in the hybrid model as a ratio of the amplitude modulated and frequency modulated components of the saturating beam. These RAM production mechanisms result from the modulation of the saturating beam, the overlap of the beams in the medium, and the differential absorption of the sidebands in the medium. While the first mechanism has been previously reported the latter two are discussed here in detail for the first time. RAM generated by the modulators used (acousto-optic or electro-optic modulators) was typically of the order of 10% to 12%, depending on the excursion of the created sidebands. RAM generated by an asymmetric beam overlap with the modulators used was found to be as large as 30%. A combination of these two independent mechanisms can be used to provide a "RAM-free" state of the system by using one to cancel the effects of the other. The third RAM generation process--medium induced RAM--is difficult to remove but through a careful combination of absorption related parameters--namely, pump intensity, cell length, pressure and detector phase--the effects of RAM can be removed, leading to a distortion free MTS signal. Further investigation into the predictions provided by the hybrid model shows that there is a complex relationship between cell length and the optimum pressure required for maximum signal strength, such that longer cell lengths will not necessarily improve the signal strength. This is contrary to conventional thinking and is important in the MTS design process to reduce unnecessary costs and improve the signal to noise ratio and frequency accuracy. Optimisation of frequency stabilised laser systems using MTS are generally performed using trial and error. Comparison of these optimum parameter values to those predicted by the hybrid model show that for popular wavelengths such as 532 nm they are similar. In addition, the hybrid model is able to predict the frequency shifts that arise within the system parameters used and has shown that existing systems being used at 532 nm, 633 nm and 778 nm could improve their signal to noise ratio and accuracy through a variation in the parameters. A methodology based on the hybrid model is presented that can be used to calculate the optimum parameters for maximum signal strength and a "RAM-free" state for any wavelength. This systematic approach can therefore be used to guide the design of actual frequency stabilised laser systems prior to and during the design process.
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4

Smowton, P. M. "The frequency stabilisation of laser diodes for industrial applications." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319933.

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Young, John Scott. "Performance of phase noisy optical systems with frequency stabilisation." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13038.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1991.
Includes bibliographical references (leaves 80-82).
by John Scott Young.
M.S.
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6

Paczkowski, Sarah [Verfasser]. "Laser Frequency Stabilisation and Interferometer Path Length Differences during the LISA Pathfinder Satellite Mission / Sarah Paczkowski." Hannover : Gottfried Wilhelm Leibniz Universität, 2021. http://d-nb.info/123822234X/34.

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7

Sträßer, Alexander. "Neue Prinzipien zur Realisierung von gepulsten, frequenzstabilisierten Lasern mit hoher mittlerer Leistung und exzellenter Strahlqualität." Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1749/.

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Wasserdampf in der Stratosphäre und Troposphäre ist eines der wichtigsten atmosphärischen Treibhausgase. Neben seiner Bedeutung für das Klima hat es großen Einfluss auf die Bildung von polaren stratosphärischen Wolken sowie auf die atmosphärische Chemie. Weltweit erstmalig soll innerhalb eines Forscherverbundes in Deutschland ein leistungsstarkes, mobiles, abtastendes Wasserdampf-DIAL zur dreidimensional hochaufgelösten Messung des atmosphärischen Wasserdampfs entwickelt werden. Mit dem Wasserdampf-DIAL können Wasserdampfkonzentrationen in der Atmosphäre mit hoher zeitlicher und räumlicher Auflösung gemessen werden. Das DIAL basiert auf einem Titan-Saphir-Laser oder einem dazu alternativen OPO-Laser (optisch parametrischer Oszillator). Der für das optische Pumpen dieser Laser nötige Pumplaser wurde im Rahmen dieser Arbeit in der Arbeitsgruppe Nichtlineare Optik des Instituts für Physik der Universität Potsdam entwickelt. Ein hochauflösendes, mobiles DIAL erfordert einen Pumplaser mit großen Pulsenergien, guter Strahlqualität und einer hohen Effizienz. Um diese Ziele zu erreichen, wurde ein MOPA-System (Master Oscillator Power Amplifier) mit Frequenzstabilisierung auf der Basis von doppelbrechungskompensierten, transversal diodengepumpten Laserstäben entwickelt und untersucht. Auf dem Weg dahin wurden unterschiedliche Realisierungsmöglichkeiten des MOPA-Systems geprüft. Im Rahmen dessen wurden die Festkörperlasermaterialien Yb:YAG [1], kerndotierte Nd:YAG-Keramik [2] und herkömmliches Nd:YAG vorgestellt und hinsichtlich ihrer Eignung für dieses MOPA-System untersucht. Nachdem die Entscheidung für Nd:YAG als laseraktives Material gefallen war, konnte darauf aufbauend die Konzeptionierung des Lasersystems auf der Basis von Verstärkungsrechnungen vorgenommen werden. Die entwickelte Verstärkungsrechnung trägt den Tatbeständen von realen Systemen Rechnung, indem radiusabhängige Intensitäten und eine radiale, nicht homogene Inversionsdichte berücksichtigt werden. Die Frequenzstabilisierung des gepulsten Oszillators (Frequenzstabilität von 1 MHz) wurde mittels des Pound-Drever-Hall-Verfahrens vorgenommen. Mit der Heterodynmethode wird die Frequenzstabilität des Oszillators gemessen. Nach Untersuchungen über verschiedene Konfigurationen für lineare und ringförmige Oszillatoren, wurde ein Ringoszillator mit zwei Laserköpfen aufgebaut, in welchen von außen mit einem Laser fester Frequenz eingestrahlt wird. Dieser emittiert bei einer Wiederholrate von 400 Hz eine Pulsenergie von Eout = 21 mJ bei nahezu beugungsbegrenzter Strahlqualität (M2 < 1,2). Die Verstärkung dieser Laserpulse erfolgte zunächst durch eine Vorverstärkerstufe und anschließend durch zwei doppelbrechungskompensierte Hauptverstärker im Doppeldurchgang. Eine gute Strahlqualität (M2 = 1,75) konnte unter anderem erzielt werden, indem der Doppeldurchgang durch die Hauptverstärker mit einem phasenkonjugierenden Spiegel (SF6), auf der Basis der stimulierten Brillouin Streuung, realisiert wurde. Der entwickelte Laser emittiert Pulse mit einer Länge von 25 ns und einer Energie von 250 mJ. Insgesamt wurde ein bisher einmaliges Lasersystem entwickelt. In der Literatur sind die erreichte Frequenzstabilität, Strahlqualität und Leistung in dieser Kombination bisher nicht dokumentiert. In der Zukunft soll durch den Einsatz von kerndotierten, keramischen Lasermaterialien, höheren Pumpleistungen der Hauptverstärker und phasenkonjugierenden Spiegeln aus Quarz die Pulsenergie des Systems weiter erhöht werden. [1] M. Ostermeyer, A. Straesser, “Theoretical investigation of Yb:YAG as laser material for nanosecond pulse emission with large energies in the joule range”, Optics Communications, Vol. 274, pp. 422-428 (2007) [2] A. Sträßer and M. Ostermeyer, “Improving the brightness of side pumped power amplifiers by using core doped ceramic rods”, Optics Express, Vol. 14, pp. 6687- 6693 (2006)
Vapour in the stratosphere and troposphere is one of the most important atmospheric greenhouse gases. Apart from its importance for the climate it has a great influence on the formation of polar stratospheric clouds as well as the atmospheric chemistry. A German research group is currently developing the world’s first powerful, mobile, screening vapour-DIAL, which can measure the atmospheric vapour three-dimensionally and in high resolution. Vapour concentrations in the atmosphere can be measured in high temporal and local resolution with this vapour-DIAL. The DIAL is based on a titan-saphire-laser or an alternative OPO-laser (Optical Parametric Oscillator). The seeding-laser, which is needed in order to seed those lasers, was developed in the course of this work by the research group for nonlinear optics in the institute for physics at the University of Potsdam. A highly-resolutive, mobile DIAL needs a seeding-laser with high pulse energy, excellent beam quality and high efficiency. In order to realise this, a frequency stabilised MOPA-System (Master Oscillator Power Amplifier) was developed, which based on birefringence-compensated, transversally diode-pumped laser rods. During the research process several ways to realise the MOPA-System were investigated. In this process the solid laser materials Yb:YAG [1], core-doped Nd:YAG-Ceramics [2] und conventional Nd:YAG were introduced and their suitability for the MOPA-System was investigated. After the choice for Nd:YAG as laser-active material was made, the concept of the laser-system could be developed based on amplification-calculations. The amplification-calculation meets the requirements of real systems, because intensities depending on diameter and a radial, non-homogeneous inversion density are being taken into consideration. The frequency of the pulsed oscillator (frequency stabilisation of 1 MHz) was stabilised by means of the Pound-Drever-Hall-Method. The frequency stability of the oscillator is measured using the Heterodyn-Method. After the investigation of different configurations for linear and circular oscillators a circular oscillator with two laser heads was set up, which is injection-seeded by a second laser with a stable frequency. At a repetition rate of 400 Hz the circular oscillator emits a pulse energy of Eout = 21 mJ with almost diffraction-limited beam quality (M2 < 1.2). These laser pulses were first amplified by a pre-amplifier and afterwards by two birefringence compensated main-amplifier in doublepass. Among other factors, an excellent beam quality (M2 = 1.75) could be reached by the doublepass through the main amplifier realised with a phase conjugating mirror (SF6) based on stimulated Brillouin-scattering. The developed laser emits pulses that are of 25 ns length and have an energy of 250 mJ. A currently unique laser system was developed. In the research findings there are no previous documents of the combination of the reached stability of frequency, beam quality and power in one system. In the future the pulse energy of the system is to be further increased through the use of core-doped, ceramic laser material, a higher pump power of the main amplifiers and phase-conjugating mirrors made of quartz. [1] M. Ostermeyer, A. Straesser, “Theoretical investigation of Yb:YAG as laser material for nanosecond pulse emission with large energies in the joule range”, Optics Communications, Vol. 274, pp. 422-428 (2007) [2] A. Sträßer and M. Ostermeyer, “Improving the brightness of side pumped power amplifiers by using core doped ceramic rods”, Optics Express, Vol. 14, pp. 6687- 6693 (2006)
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Grishina, Vera. "Blue laser for precision spectroscopy : toward optical frequency standard referenced to laser cooled calcium atoms." University of Western Australia. School of Physics, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0046.

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Optical frequency standards with the reference to a narrow electronic transition of a laser-cooled collection of neutral atomic particles are becoming essential tools of research in modern precision physics experiments. In the core of a building block of an optical frequency standard is the optical continuous wave laser that has a good spectral purity of the emitted light. Such a stable optical oscillator is highly desirable in high resolution spectroscopy, if it emits in a good quality beam at a short visible wavelength. This Master thesis explores efficient techniques for building such an optical frequency source intended for use in the cooling and trapping of Calcium atoms scheme. The strong dipole transition at the blue wavelength in the atomic Calcium is needed to reduce the kinetic energy of atoms by nearly six orders of magnitude. A further reduction in the thermal energy of the laser cooled atoms is required to locate with ultra-high precision the 400 Hz narrow clock transition of the stable 40Ca isotope. The experimental methods that achieve this and approach sub-microkelvin temperature of the laser cooled bosonic isotopes of alkaline earths are inspected. The blue laser with a uniform intensity distribution in the beam is useful to maintain the trapped number of cold atoms during these experiments. The spectroscopic properties of the relative transitions in Calcium atom are also reviewed following relevant publications in the area. The constructed blue laser can be used as a primary wavelength source in the lasers network for cooling and trapping of Calcium atoms. These experiments will constitute part of the project to build an optical atom clock referenced to 40Ca narrow linewidth transition. The blue laser is constructed by generating second harmonic in a Potassium Niobate crystal, which is temperature controlled to use a type-I noncritical phase-matching of the optical nonlinear process. The power of the intracavity-generated second harmonic depends on the resonance properties of the optical resonator where this nonlinear crystal is placed. The study is aimed at characterising the designed optical resonator and the experimental parameters that describe it. The formula is derived that relates the resonance power enhancement coefficient with finesse and the power coupling contrast of a passive optical cavity. The obtained relationship is verfied during the experiments. The produced efficiency of the intracavity second harmonic generation is approx. 0.0023 mWblue/(mWred)2. The research work also examines the noise characteristics of the infrared diode laser that is used as a pump source for the intracavity generated second harmonic and determines the spectroscopic precision of the produced blue light. The frequency locking experiment is analysed using the unbalanced scheme of the polarisation stabilisation technique. The designed optical buildup cavity became a part of the unbalanced frequency discriminator in such a scheme. The results demonstrate high gain of frequency noise suppression of the stabilised laser. The unbalanced arrangement of the H}ansch-Couillaud technique has been possible due to a very low amplitude noise of semiconductor lasers.
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Guionie, Marie. "Lasers à fibres bifréquences bipolarisations : stabilisation et montée en fréquence du battement." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S059.

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Cette étude porte sur les lasers à fibres bifréquences bipolarisations. Le contrôle de la différence de fréquence de ces lasers représente un enjeu important en photonique microonde. En effet, maîtriser le battement permettrait la réalisation de sources compactes et à faible bruit visant des applications de métrologie ou télécom. Nous travaillons ici sur des sources émettant à 1,5 μm, de type DFB ou DBR, soit dopés Er soit co-dopés Er-Yb. Ils présentent une fréquence de battement d'environ 1 GHz pour les DFB, et 100 MHz pour les DBR. Les objectifs de la thèse ont été, d'abord de stabiliser le battement, puis d'explorer différentes méthodes pour modifier la biréfringence de la fibre et ainsi accroître la fréquence de battement. Nous avons d'abord utilisé la méthode de stabilisation par boucle à verrouillage de phase pour asservir le battement sur une fréquence de référence. En nous servant de la diode de pompe comme actuateur, nous avons réussi à stabiliser des battements entre 300 MHz et 10 GHz pendant plusieurs jours. Ensuite, nous avons mis en place une méthode de stabilisation par réinjection optique décalée en fréquence. Un modèle théorique basé sur des équations-bilan couplées a été utilisé et a permis de retrouver les observations expérimentales. En stabilisant le battement sur une référence extérieure, différents régimes dynamiques ont été observés. Dans la zone stable, on réduit le bruit de phase jusqu'à −100 dBc/Hz à 1 kHz de la porteuse. Puis, nous avons couplé le montage de la réinjection optique a une ligne à retard, afin de stabiliser efficacement le battement sur lui-même. Enfin, nous avons étudié plusieurs pistes pour augmenter la fréquence de battement des lasers DBR pour répondre aux besoins des applications. Nous avons pu suivre en temps réel la modification de biréfringence photo-induite par un faisceau UV. Nous avons aussi étudié une méthode de modification réversible de la biréfringence, en exploitant l'effet élasto-optique. Quelque soit la méthode employée, nous avons observé un accroissement de la fréquence de battement depuis 100 MHz jusqu'à plus de 10 GHz dans le meilleur des cas
This work is about dual-polarization dual-frequency fibers lasers. The control of the frequency difference of these lasers is a major challenge in microwave photonics. Controlling the beat frequency could allow compact and low-noise sources, in order to develop applications in metrology or telecom. Here, we focus on 1.5 μm sources, in either DFB or DBR configurations, made of Er-doped or co-doped Er:Yb silica fibres. Their beat frequency is about 1 GHz for DFB lasers, and 100 MHz for DBR lasers. This thesis investigates several methods to stabilize the beat note, then to modify the fiber birefringence, to increase the beat frequency. First, an optical phase-locked loop method is used to lock the beat note on a frequency reference. By using the pump diode as an actuator, we have successfully stabilized beat frequencies between 300 MHz and 10 GHz for days. We then study a stabilization method by frequency-shifted optical feedback. A theoretical model based on rate equations model is used and allows to retrieve the experimental observations. We observe different dynamical regimes by locking the beat note on a reference frequency. In the stable area, we reduce the phase noise to −100 dBc/Hz at 1 kHz from the carrier. Next, we have mixed the set-up of the injection-locking to a delay line, in order to effectively stabilize the beat note on itself. Finally, various approaches have been explored to increase the beat frequency of DBR lasers, to the needs of applications. It has been possible to continuously monitor the impact of a UV beam on the fiber birefringence. We also studied a method for reversible modification of the birefringence, exploiting the elasto-optical effect. Regardless of the method used, we observed an increase in the beat frequency from 100 MHz to more than 10 GHz in the best case
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Toufayli, Laila. "Stabilisation polynomiale et contrôlabilité exacte des équations des ondes par des contrôles indirects et dynamiques." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00780215.

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La thèse est portée essentiellement sur la stabilisation et la contrôlabilité de deux équations des ondes moyennant un seul contrôle agissant sur le bord du domaine. Dans le cas du contrôle dynamique, le contrôle est introduit dans le système par une équation différentielle agissant sur le bord. C'est en effet un système hybride. Le contrôle peut être aussi applique directement sur le bord d'une équation, c'est le cas du contrôle indirecte mais non borne. La nature du système ainsi coupledépend du couplage des équations, et ceci donne divers résultats par la stabilisation (exponentielle et polynomiale) et la contrôlabilité exacte (espace contrôlable). Des nouvelles inégalités d'énergie permettent de mettre en oeuvre la Méthode fréquentielle et la Méthode d'Unicité de Hilbert.
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Book chapters on the topic "Frequency stabilisation"

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Heilmann, R., and J. Kuschel. "Frequency Stabilisation of Diode Pumped Solid-State Lasers for Application in Free-Space Communication." In Laser in der Technik / Laser in Engineering, 792–95. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-662-08251-5_171.

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Chesnoy, J., and L. Fini. "Stabilisation of a CPM Dye Laser Synchronously Pumped by a Frequency Doubled ML YAG Laser." In Springer Series in Chemical Physics, 14–16. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-82918-5_5.

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Abramski, K. M., and D. R. Hall. "Frequency Stabilisation of Lasers." In The Physics and Technology of Laser Resonators, 117–31. CRC Press, 2020. http://dx.doi.org/10.1201/9781003069508-9.

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Lynch, Sharon A., Andrew F. Rowley, Matt Longshaw, Shelagh K. Malham, and Sarah C. Culloty. "Diseases of molluscs." In Invertebrate Pathology, 171–216. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198853756.003.0008.

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Phylum Mollusca is a large and diverse group of invertebrate protostomes of over 85,000 species including gastropods, cephalopods and bivalves. Molluscs are the largest marine phylum. Marine molluscs are economically important as a high protein food source for humans and provide ecosystem services including nutrient recycling, carbon sequestration, sediment stabilisation and bioturbation. Molluscs are harvested by traditional fishing but are increasingly cultured in many coastal communities worldwide. Hence most information on pathogens and disease is known in molluscs of commercial significance. Bivalves (oysters, mussels, clams, scallops, cockles) are susceptible to a wide range of diseases caused by viruses (e.g. ostreid herpes virus-1 and variants) bacteria (e.g. Vibrio spp., Nocardia crassostreae, Roseovarius spp., rickettsia and Mycobacterium spp.), microsporidians (e.g. Steinhausia spp.), paramyxids (Marteilia refringens and M. pararefringens), haplosporidans (e.g. Haplosporidium nelsoni, Minchinia spp., and Bonamia ostreae) and macroparasites (e.g. trematodes, copepods and nematodes). The gastropod abalone are susceptible to viruses (e.g. Abalone Viral Ganglioneuritis) and bacteria (Rickettsiales-like organism). Of particular importance is Pacific oyster mortality syndrome (POMS) that is polymicrobial in nature with initial infection by ostreid herpesvirus with subsequent bacterial infections by a variety of vibrios, and marteiliosis. In North America, since the early 1950’s there have been episodes of diseases including Dermo disease, caused by Perkinsus marinus, and MSX disease caused by H. nelson in Crassostrea spp. Globally, it is recognised that marine diseases including those that impact molluscs are becoming more frequent and severe due to climate change, in particular increasing seawater temperature, and human activities.
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"In any case, covering may be impracticable for other reasons. Many processes as they are currently designed depend upon at least visual access by operators for process control, and in other instances the production of odorous chemicals such as hydrogen sulphide can be accompanied by the formation of methane, giving a potential fire or explosion hazard. 1.1.1. Odours .from the Spreading of Sludge and Slurries on Land The chimney, originally devised to increase draught through fires and to provide smoke extraction, has found extensive use in many industries to aid the dispersion of odour. The extra height gained by the point of emission is frequently enough to give the extra dilution required to reduce the risk of odour nuisance at even relatively nearby properties. This is an option that is not open to the farmer or the sewage works operator. The cost and practicability of enclosing the processes used in sewage treatment varies considerably, but in the disposal of sludge or animal slurries to land there is never a realistic option that the dispersion of odours once transferred to the gas phase might be effectively controlled. For the prevention of nuisance therefore there are two possibili­ ties. First, the formation or release of odorous chemical species can be discouraged. In practice this usually means the prevention of reducing conditions (negative redox potential) and possibly the prior removal of certain key compounds. Second, the time of contact between the sludge/ slurry and the air can be reduced, for example by ploughing in or sub-surface injection, and the act of spreading can be timed to coincide with favourable atmospheric conditions. These two approaches can of course be used in combination. Both approaches naturally add to the cost of sludge disposal, and for the sewage works manager add to the risk that farmers might be less willing to accept sludge to land, causing a greater problem still. For the fanner, sewage sludge can be a useful source of cheap nitrogen, though of unspecified strength, and also of much needed soil structure, but the imposition of no-grazing periods after application can add to the cost taken as a whole. A further problem, especially for farmers with arable crops is that the demand for soil nutrients and the practicability of spreading and ploughing in are seasonal, whereas a sludge and slurry are produced at a more or less constant rate. In the case of slurries, seme form of storage is inevitable, and commonly takes place in open pits. Scxne digestion and therefore stabilisation takes place during storage, reducing the capacity of the slurry to cause odour nuisance, and as long as the surface crust is not disturbed, little odour results. It is the emptying of slurry pits that gives rise to the release of odour. 2. P rin ciple, Sources, of Odour at .^ weg e .lreatment Works." In Odour Prevention and Control of Organic Sludge and Livestock Farming, 146. CRC Press, 1986. http://dx.doi.org/10.1201/9781482286311-58.

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Conference papers on the topic "Frequency stabilisation"

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Li Shen, Mike Barnes, R. Preece, and JV Milanovic. "Frequency stabilisation using VSC-HVDC." In 2016 IEEE Power and Energy Society General Meeting (PESGM). IEEE, 2016. http://dx.doi.org/10.1109/pesgm.2016.7741259.

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Schediwy, Sascha, Andre Luiten, Guido Aben, Kenneth Baldwin, Yabai He, Brian Orr, and Bruce Warrington. "Microwave frequency transfer with optical stabilisation." In 2012 European Frequency and Time Forum (EFTF). IEEE, 2012. http://dx.doi.org/10.1109/eftf.2012.6502369.

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Mondin, Linda, Alain Brillet, C. Nary Man, and Jacques Berthon. "Laser frequency stabilisation for space applications." In International Conference on Space Optics 2006, edited by Errico Armandillo, Josiane Costeraste, and Nikos Karafolas. SPIE, 2017. http://dx.doi.org/10.1117/12.2308092.

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Richards, Christopher J., Thomas J. Smart, Philip H. Jones, and David Cubero. "Low frequency dynamical stabilisation in optical tweezers." In SPIE Nanoscience + Engineering, edited by Kishan Dholakia and Gabriel C. Spalding. SPIE, 2015. http://dx.doi.org/10.1117/12.2190822.

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Webb, D. J., J. D. C. Jones, and D. A. Jackson. "Laser Diode Frequency Stabilisation Techniques For Interferometric Sensors." In Fibre Optics '88, edited by Lionel R. Baker. SPIE, 1988. http://dx.doi.org/10.1117/12.947532.

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Vaishali, S., and A. Jamna. "Design of matrix converter in windmill for frequency stabilisation." In 2014 International Conference on Information Communication and Embedded Systems (ICICES). IEEE, 2014. http://dx.doi.org/10.1109/icices.2014.7034163.

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Thottungal, Rani, P. Anbalagan, T. Mohanaprakash, A. Sureshkumar, and G. V. Prabhu. "Frequency Stabilisation in Multi Area System Using HVDC Link." In 2006 IEEE International Conference on Industrial Technology. IEEE, 2006. http://dx.doi.org/10.1109/icit.2006.372243.

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Kobtsev, Sergey, Stepan Kandrushin, and Andrey Potekhin. "New approach to long-term frequency stabilisation of radiation of single-frequency lasers." In International Conference on Lasers, Applications, and Technologies '07, edited by Valentin A. Orlovich, Vladislav Panchenko, and Ivan A. Scherbakov. SPIE, 2007. http://dx.doi.org/10.1117/12.753015.

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Ribeiro e Silva, S., and J. M. Varela. "Ship Gyroscopic Roll Stabilisation." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79530.

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Abstract A thorough understanding of the interaction of waves with ships is a vital factor in the safe and economical technology design. Considerable advances have been made recently in the modelling of wave hydrodynamics and wave-structure interaction. Wave diffraction analysis using 2D Strip Theory (ST) or 3D Boundary Element Methods (BEM) based on potential flow theory is now standard with linear and second-order theory in the frequency domain. In case an assessment of a new ship roll stabilisation system of the gyroscopic type is seen as desirable, no ready to use numerical tool to predict the performance of the wave-structure interaction is available. Therefore, for smaller vessels with a certain advance speed, such a patrol boats or pleasure crafts further developments must be applied to a BEM method to take into account speed corrections plus a standard ST tool in order to include the roll stabilisation effect that could be attained using a dedicated gyroscopic roll stabilisation system installed aboard. In this framework, the proposed work consists of exploring the application of an adapted BEM method with speed corrections, plus a standard ST to study the wave-structure interactions of an unstabilised ship and a ship fitted with a Gyroscopic Roll Stabilisation (GRS) system by considering the case study of a small patrol boat in a seaway. The main objective of this study is to assess the performance of this GRS concept and calculate the operability index of this class of vessels (percentage of time the vessel complies with user pre-defined limiting criteria) for a certain design point using long term statistics, so that complex non-linear responses in waves will be neglected at this stage.
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Affolderbach, C., G. Mileti, D. Slavov, C. Andreeva, and S. Cartaleva. "Comparison of simple and compact "Doppler" and "sub-Doppler" laser frequency stabilisation schemes." In 18th European Frequency and Time Forum (EFTF 2004). IEE, 2004. http://dx.doi.org/10.1049/cp:20040888.

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