Thematische Bibliographien / Specral linewidth

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Auswahl der wissenschaftlichen Literatur zum Thema „Specral linewidth“

Autor: Grafiati

Veröffentlicht am 28. Juni 2021

Zuletzt aktualisiert am 5. Februar 2022

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Zeitschriftenartikel zum Thema "Specral linewidth"

Wenzel, Hans, Markus Kantner, Mindaugas Radziunas und Uwe Bandelow. „Semiconductor Laser Linewidth Theory Revisited“. Applied Sciences 11, Nr. 13 (28.06.2021): 6004. http://dx.doi.org/10.3390/app11136004.

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More and more applications require semiconductor lasers distinguished not only by large modulation bandwidths or high output powers, but also by small spectral linewidths. The theoretical understanding of the root causes limiting the linewidth is therefore of great practical relevance. In this paper, we derive a general expression for the calculation of the spectral linewidth step by step in a self-contained manner. We build on the linewidth theory developed in the 1980s and 1990s but look from a modern perspective, in the sense that we choose as our starting points the time-dependent coupled-wave equations for the forward and backward propagating fields and an expansion of the fields in terms of the stationary longitudinal modes of the open cavity. As a result, we obtain rather general expressions for the longitudinal excess factor of spontaneous emission (K-factor) and the effective α-factor including the effects of nonlinear gain (gain compression) and refractive index (Kerr effect), gain dispersion, and longitudinal spatial hole burning in multi-section cavity structures. The effect of linewidth narrowing due to feedback from an external cavity often described by the so-called chirp reduction factor is also automatically included. We propose a new analytical formula for the dependence of the spontaneous emission on the carrier density avoiding the use of the population inversion factor. The presented theoretical framework is applied to a numerical study of a two-section distributed Bragg reflector laser.

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Boller, Klaus-J., Albert van Rees, Youwen Fan, Jesse Mak, Rob Lammerink, Cornelis Franken, Peter van der Slot et al. „Hybrid Integrated Semiconductor Lasers with Silicon Nitride Feedback Circuits“. Photonics 7, Nr. 1 (21.12.2019): 4. http://dx.doi.org/10.3390/photonics7010004.

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Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth, as well as compatibility for embedding into integrated photonic circuits, are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si 3 N 4 in SiO 2 ) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around a 1.55 μ m wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.

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LIN, JIE-LI, YU-YAN LIU, HONG-PING LIU, YUAN-QING QUO, XIAO-YONG LIU, FENG-YAN LI und JIN-RUI LI. „MEASUREMENT OF PRESSURE-BROADENING LINEWIDTHS OF NO FROM THE FITTING OF LMR SPECTRA WITH CORRECTIONS OF INSTRUMENTAL BROADENING“. Modern Physics Letters B 14, Nr. 11 (10.05.2000): 401–7. http://dx.doi.org/10.1142/s0217984900000537.

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For absorption lines, the distortion of spectral lines by experimental spectrometers must be considered in measuring linewidth which has been investigated by many authors. While in the derivative spectrum, we managed to give the corrections of instrumental broadening and distortion to obtain accurate linewidths. We developed a universal fitting program which was explored together with the method of correction in the fundamental band spectra of LMR of NO. The uncorrected halfwidths were compared with the corrected values, which were obtained from the program. The results of comparison are very satisfactory and demonstrate their useful application to analyze experimental spectra.

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Anikushina, T. A., M. G. Gladush, A. A. Gorshelev und A. V. Naumov. „Single-molecule spectromicroscopy: a route towards sub-wavelength refractometry“. Faraday Discussions 184 (2015): 263–74. http://dx.doi.org/10.1039/c5fd00086f.

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We suggest a novel approach for spatially resolved probing of local fluctuations of the refractive index n in solids by means of single-molecule (SM) spectroscopy. It is based on the dependence T₁(n) of the effective radiative lifetime T₁ of dye centres in solids on n due to the local-field effects. Detection of SM zero-phonon lines at low temperatures gives the values of the SM natural spectral linewidth (which is inversely proportional to T₁) and makes it possible to reveal the distribution of the local n values in solids. Here we demonstrate this possibility on the example of amorphous polyethylene and polycrystalline naphthalene doped with terrylene. In particular, we show that the obtained distributions of lifetime limited spectral linewidths of terrylene molecules embedded into these matrices are due to the spatial fluctuations of the refractive index local values.

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MENON, P. SUSTHITHA, KUMARAJAH KANDIAH und SAHBUDIN SHAARI. „VARIATION OF MQW DESIGN PARAMETERS IN A GaAs/InP-BASED LW-VCSEL AND ITS EFFECTS ON THE SPECTRAL LINEWIDTH“. Journal of Nonlinear Optical Physics & Materials 19, Nr. 02 (Juni 2010): 209–17. http://dx.doi.org/10.1142/s0218863510005273.

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This paper reports on the simulative and comparative study on the effects of multi quantum well (MQW) design parameters on the spectral linewidth of a wafer-bonded GaAs/InP -based, 1.5 μm long-wavelength vertical-cavity surface-emitting laser (LW-VCSEL). The device employs InGaAsP MQWs sandwiched between GaAs/AlGaAs and GaAs/AlAs distributed Bragg reflectors (DBR) and utilizes a bottom-emitting, air-post design for current confinement. Among the modeled LW-VCSEL devices, the best linewidth achieved was 41.29 MHz at a peak wavelength of 1.57 μm for 8 MQWs with well thicknesses of 5.5 nm each and barrier thicknesses of 8 nm; equivalent to the experimental device developed in the past. Comparison of linewidth values calculated using developed analytical equations that link the MQW parameters to the spectral linewidth versus the actual linewidth from fabricated devices yields error ratios of ~ 6% proving a robust approximation has been achieved.

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Gao, W., Z. W. Lu, W. M. He, Y. K. Dong und W. L. J. Hasi. „Characteristics of amplified spectrum of a weak frequency-detuned signal in a Brillouin amplifier“. Laser and Particle Beams 27, Nr. 3 (24.06.2009): 465–70. http://dx.doi.org/10.1017/s0263034609990164.

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AbstractWe will theoretically and experimentally study the effect of the linewidth and the frequency of a weak detuned signal on its amplified spectrum in the Brillouin amplifier. We will show that the spectral profile of the input signal is preserved during amplification only when the signal linewidth is much narrower than the Brillouin linewidth of the amplifier. If the signal linewidth is near or above the Brillouin linewidth, the frequency shift of the amplified signal with respect to the pump will be close to the Brillouin shift of the amplifier, and will be independent of the frequency shift of the input signal.

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Nguyen, Thanh-Phuong, Hans Wenzel, Olaf Brox, Frank Bugge, Peter Ressel, Max Schiemangk, Andreas Wicht, Tran Quoc Tien und Günther Tränkle. „Spectral Linewidth vs. Front Facet Reflectivity of 780 nm DFB Diode Lasers at High Optical Output Power“. Applied Sciences 8, Nr. 7 (09.07.2018): 1104. http://dx.doi.org/10.3390/app8071104.

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The influence of the front facet reflectivity on the spectral linewidth of high power DFB (distributed feedback) diode lasers emitting at 780 nm has been investigated theoretically and experimentally. Characterization of lasers at various front facet reflections showed substantial reduction of the linewidth. This behavior is in reasonable agreement with simulation results. A minimum linewidth of 8 kHz was achieved at an output power of 85 mW with the laser featuring a front facet reflectivity of 30%. The device with a front facet reflectivity of 5% reached the same linewidth value at an output power of 290 mW.

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Kunii, T., und Y. Matsui. „Narrow spectral linewidth semiconductor lasers“. Optical and Quantum Electronics 24, Nr. 7 (Juli 1992): 719–35. http://dx.doi.org/10.1007/bf00620152.

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TADA, K., A. YAMANAKA und N. KARASAWA. „BROADBAND COHERENT ANTI-STOKES RAMAN SCATTERING MICROSPECTROSCOPY USING THE SOLITON PULSES FROM A PHOTONIC CRYSTAL FIBER — OBSERVATION OF RAMAN LINE IN DIAMOND POWDERS“. Journal of Nonlinear Optical Physics & Materials 19, Nr. 04 (Dezember 2010): 723–28. http://dx.doi.org/10.1142/s0218863510005649.

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We have investigated broadband coherent anti-Stokes Raman scattering (CARS) microspectroscopy using the soliton pulses from a photonic crystal fiber. CARS spectrum shows a dispersive shape due to the contributions from a frequency-independent nonresonant component and from a resonant component that corresponds to spontaneous Raman scattering. To extract the resonant component from the CARS spectrum, the functional form of this component was commonly assumed to be a simple Lorentzian function and a nonlinear fitting procedure was used previously. In this study, we derived a CARS spectral function that takes into account the finite spectral width of a pump pulse and the CARS spectrum of diamond powders was fitted using the derived spectral function. It was found that the linewidth obtained using this function agreed with the linewidth of spontaneous Raman scattering much better than the linewidth obtained using a CARS spectral function commonly used previously.

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Weng, Hai-Zhong, Yong-Zhen Huang, Xiu-Wen Ma, Fu-Li Wang, Ming-Long Liao, Yue-De Yang und Jin-Long Xiao. „Spectral Linewidth Analysis for Square Microlasers“. IEEE Photonics Technology Letters 29, Nr. 22 (15.11.2017): 1931–34. http://dx.doi.org/10.1109/lpt.2017.2752232.

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Dissertationen zum Thema "Specral linewidth"

Beneš, Pavel. „Měření základních parametrů optických a optoelektronických komponent“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442446.

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This diploma thesis deals with optical and optoelecronic components. The first part of the work describes the optical paths and methods of their measurement. The second part describes the coupler, circulator and isolator. Further described is a laser diode, a photodetector and a modulator. The third part describes the measurement procedure of the coupler, circulator, isolator, laser diode, photodetector and modulator. The measured values are compared with the catalog values.

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Tavenner, Kruger Sasha Dawn. „Homogeneous linewidth and spectral diffusion in semiconductor nanocrystals /“. view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251884311&sid=3&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 164-170). Also available for download via the World Wide Web; free to University of Oregon users.

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Lynch, Richard James. „Investigation into the spectral linewidth of InGaN LEDs“. Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420843.

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Flint, Nicholas John. „A study of linewidth variation in the E.S.R. spectra of some radical anions“. Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329999.

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Hsu, Long. „Wavelength dependence of the spectral linewidth of a grating-tuned CW single-frequency external-cavity strained quantum well InGaAs/AlGaAs Grinsch diode laser“. Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28059.

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Duan, Jianan. „Dynamic and nonlinear properties of quantum dot lasers for photonic integrated circuits on silicon“. Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLT050.

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La photonique sur silicium permet de palier au faible rendement et la consommation énergétique élevée des liens télécoms exploitant les câbles à paires torsadées ou les câbles coaxiaux. Cette technologie offre une versatilité exceptionnelle, de nouvelles fonctionnalités et des performances accrues pour les communications à haut-débit, les systèmes d’interconnexions optiques à courte portée et le déploiement de liaisons optiques d’une puce à une autre, d’une carte à une autre, ou d’un rack à un autre (datacom). Le silicium est un matériau semi-conducteur très efficace pour le guidage de la lumière, notamment en raison du fort contraste d’indice avec la silice. Cependant, sa bande interdite indirecte ne permet pas une émission radiative efficace. La réalisation de lasers repose donc sur des technologies hybrides de collage ou de report du matériau actif III- V (wafer-bonding, flip-chip) sur le silicium passif. Cependant, cette intégration hétérogène présente des inconvénients comme par exemple un coût élevé et une évolutivité limitée. Les lasers hybrides sur silicium sont aussi plus sensibles aux réflexions parasites provenant des transitions des différentes interfaces passives/actives. Un moyen permettant de surmonter ces inconvénients consiste à faire croître directement le matériau III-V sur le silicium. Dans ce contexte, les lasers à boîtes quantiques utilisant des atomes semi-conducteurs comme milieu de gain sont des candidats très prometteurs en raison de leur compacité, de leur grande stabilité thermique et d’une tolérance accrue aux défauts structuraux. Certaines applications comme les systèmes cohérents, les futures horloges atomiques intégrées sur puces et les radars où la sensibilité aux bruits de fréquence et d’intensité influe fortement le taux d’erreur binaire requièrent l’utilisation d’émetteurs optiques à très faible bruit. Dans une première partie, cette thèse révèle le potentiel de lasers à boîtes quantiques InAs/InP présentant une largeur de raie spectrale intrinsèque de 80 kHz et un bruit relatif d’intensité inférieur à -150 dB/Hz. A cet effet, il est montré qu’un faible couplage vertical entre les états liés est plus approprié pour une réduction du bruit d’intensité notamment grâce à la suppression du bruit de porteurs associée à l’état excité. Dans une deuxième partie, les propriétés dynamiques et non- linéaires des lasers à boîtes quantiques directement épitaxiés sur silicium sont étudiées. Comme susmentionné, les lasers intégrés de manière hétérogène sur le silicium sont plus sensibles aux réflexions parasites. Combinées à une rétroaction optique externe, la stabilité du laser peut s’en trouver fortement affectée. Sachant qu’il n’existe pas à ce jour d’isolateurs optiques intégrés sur puce ayant un taux d’isolation suffisant, le développement d’émetteurs insensibles aux rétroactions est un objectif majeur. Cette thèse présente notamment un résultat de transmission sans erreur à partir d’un laser à boîtes quantique directement épitaxié sur silicium soumis à une modulation externe à 10 Gb/s ainsi qu’à une rétroaction optique maximale de 100%. Cette insensibilité aux réflexions résulte de plusieurs propriétés remarquables comme un facteur d’élargissement spectral proche de zéro, un facteur d’amortissement élevé, un fort contraste entre les seuils d’émission des états liés, et une durée de vie des porteurs plus courte. Ces résultats permettent d’envisager le développement de futurs circuits intégrés photoniques sur silicium à haute performance et fonctionnant sans isolateur optique
Silicon photonics have been introduced to overcome low efficiency and high energy consumption of telecom links using twisted pairs or coaxial cables. This technology provides novel functionality and high performance for applications in high speed communication systems, short reach optical interconnects, and the deployment of optical links from chipto-chip, board-to-board or rack-to-rack (datacom). Silicon is known as a very efficient semiconductor material for waveguiding light in particular owing to the strong index contrast with silica. However, the indirect bandgap of silicon makes light emission from silicon inefficient, and other techniques such as wafer- or flipchip bonding must be investigated if light emission is to be realized. The drawbacks of such heterogeneous integration concentrate on the high cost and the limited scalability. Lasers heterogeneously integrated on silicon are also more sensitive to optical reflections originating from the transition between passive/active interfaces. The best way to overcome these drawbacks is to move on to direct epitaxial growth of IIIV materials on silicon for photonics integration. In this context, quantum dot lasers using semiconductor atoms as a gain medium are ideal because they enable smaller devices, amplification with large thermal stability and high tolerance to epitaxial defects. Ultra-low noise optical transmitters are required not only for the coherent systems but also for future chipscale atomic clocks and radar related applications because of the sensitivity to the frequency noise and intensity noise can strongly affect the bit error rates. To this end, the first part of the thesis reports an intrinsic spectral linewidth as low as 80 kHz and a relative intensity noise less than - 150 dB/Hz in InAs/InP quantum dot lasers. In particular, it is shown that a small vertical coupling is more suitable for low intensity noise operation due to the suppression of the carrier noise in the excited state. The second part of the thesis investigates the dynamic and nonlinear properties of epitaxial quantum dot lasers on silicon. As mentioned above, lasers heterogeneously integrated on silicon are more sensitive to parasitic reflections. When combined with external optical feedback, the laser stability can be dramatically affected. As no on-chip optical isolators integrated with lasers and having sufficient isolation ratio exist, the development of feedback insensitive transmitters remains a major objective. This thesis presents an error-free transmission of an epitaxial quantum dot laser on silicon externally modulated at 10 Gb/s and subjected to 100% optical feedback. Such remarkable feedback insensitivity directly results from the near-zero linewidth enhancement factor, the large damping factor, the strong contrast between the ground state and excited states and a shorter carrier lifetime. These results pave the way for future high-performance photonics integrated circuits on silicon operating without optical isolators

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Sahni, Mohamed Omar. „Contribution à l'étude de techniques pour l'affinement spectral de lasers : application aux diodes à blocage de modes destinées aux télécommunications optiques cohérentes“. Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S121/document.

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Les peignes de fréquences optiques, issus de diodes à blocage de modes, font partie des candidats potentiels pour les réseaux de transmission à multiplexage en longueurs d’onde (WDM). Cependant, les modes composant leur peigne, exhibent généralement des largeurs de raie optiques relativement élevées ( 1-100 MHz), rendant ainsi incompatible leur utilisation sur un réseau WDM employant des formats de modulation avancés d’ordre supérieur. Cette thèse étudie, une solution pour palier à cette limitation. La technique utilisée, dite d’asservissement à correction aval hétérodyne, effectue un traitement du flux lumineux en sortie du laser sans agir sur ce dernier, permettant de réduire le bruit de fréquence présent sur chacune des raies et par conséquent leur largeur de raie optique. Dans une première approche, la technique est appliquée à un laser mono-fréquence. Cela a permis d’une part de valider son fonctionnement et d’autre part d’identifier les limites intrinsèques du dispositif expérimental mis en place. Ainsi, nous démontrons que le niveau de bruit de fréquence minimum permis par notre système, correspond à un spectre optique de largeur de raie optique instantanée de 50 Hz et une largeur de raie de 1,6 kHz pour un temps d’observation de 10 ms. La technique est par la suite appliquée à une diode à blocage de modes actif. Le peigne de fréquences optiques ainsi généré, est composé de 21 modes, ayant tous une largeur de raie optique intrinsèque inférieure à 7 kHz, dont 9 modes sont sub-kHz. Pour un temps d’observation du spectre optique de 10 ms, ces modes exhibent tous une largeur de raie d’environ 37 kHz. Nous démontrons ainsi l’impact de la gigue d’impulsions sur les performances de la technique et nous soulignons l’intérêt d’une telle cohérence, pour le domaine des télécommunications optiques cohérentes (transmissions WDM cohérentes de type m-QAM avec des constellations d’ordre élevé, compatibles avec des débits multi-Tbit/s par raie). En dernier lieu, nous abordons une seconde technique consistant à pré-stabiliser la fréquence d’un laser par asservissement en boucle fermée. Elle repose sur l’utilisation d’un interféromètre à fibre déséquilibré comme référence pour réduire le bruit de fréquence d’un laser, situé particulièrement en basses fréquences. Appliquée à un laser mono-fréquence, elle a permis de réduire son bruit de fréquence technique conduisant ainsi à une nette amélioration de sa largeur de raie intégrée sur 3 ms, de 224 kHz à 37 kHz. Ce premier résultat représente un bon support vers l’exploration du potentiel des diodes à blocage de modes pour des applications métrologiques
Optical frequency combs obtained from mode-locked laser diodes are potential candidates for WDM networks. However, their lines exhibit usually a broad optical linewidth ( 1-100 MHz). Thus their use is incompatible for high order modulation formats WDM based systems. This thesis investigates one solution to overcome this limitation. It consists of using a feed-forward heterodyne technique to reduce the frequency noise of each comb-line and consequently their optical linewidths. In a first approach, the technique is applied to a single-mode laser. This allowed us to validate its proper working and to identify the intrinsic limits of the experimental device set up. The latter analysis enabled us to reveal that the minimum achievable frequency noise level by our system, corresponds to a 50 Hz intrinsic optical linewidth spectrum and a 1,6 kHz optical linewidth based on 10 ms observation time. This technique is then applied to an actively mode-locked laser diode demonstrating, at our system output, a 21-line optical frequency comb with intrinsic optical linewidths reduced to below 7 kHz. It is worth noting that 9 among them, exhibit sub-kHz linewidths. For an observation time of 10 ms, all lines share the same optical linewidth, almost equal to 37 kHz. We thus show that the timing jitter impacts the technique performances. We also highlight the relevance of such coherence level for coherent optical communication. Lastly, we study a laser frequency pre-stabilization technique based on a locking to an unbalanced fiber interferometer. When applied to a single-mode laser, the technique showed a reduction of its technical frequency noise, thus leading to a clear improvement of its integrated optical linewidth from 224 kHz to 37 kHz for 3 ms observation time. This first result provides a good support towards the exploration of mode-locked laser diodes potential for metrological applications

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Wu, Han-Wei, und 吳涵暐. „Investigation of the linewidth reduction effect of Photoluminescence spectra from silicon nanostructures“. Thesis, 2005. http://ndltd.ncl.edu.tw/handle/59324075577207535705.

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碩士
國立臺灣大學
光電工程學研究所
94
Silicon light source is the most urgently needed device in the VLSI nowadays, and will play an important role in science and in technology. The aim of this thesis is to research through what mechanism and how the silicon nanostructures affect the luminescence spectra of silicon under low temperature. Nanostructures on silicon are found to contribute to the reduction of the linewidth of its photoluminescence (PL) spectrum under low temperature. We created variant silicon nanostructures on the surface silicon wafer, inclusive of silicon nanopillar structure and silicon nanoparticles layer. The effects of the devices with silicon nanostructures are suspected to the reduct of the linewidth, to increase the relaxation time of excitons and to lower the energy of continuum excitons after theoretical simulation. In addition, excitons are bosons and obey the Bose-Einstein distribution, thus under low temperature and the carrier confinement effects of the nanostructures, mass excitons will concentrate at the lowest energy level. The linewidth reduction effect might take place and the excitons might concentrate at higher temperature under the effects of the silicon nanostructures with more compact sizes and more regular arrangement.

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Chiang, Chih-Lo, und 江志珞. „Evaluation of quantitative proton MRS analysis of amino acids by simulation of different levels of noise and spectral linewidth“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/6b66s7.

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碩士
國立中山大學
資訊工程學系研究所
102
Magnetic resonance imaging (MRI), a noninvasive technique, is broadly applied on clinical diagnosis now. Magnetic resonance spectroscopy (MRS), a method derived from MRI, can provide precise information for investigating metabolites in vivo for human beings, especially the clinical applications on brain tumors and pyogenic abscesses. In this study, we used LCModel to analyze in vivo proton MR spectra. It is a simple and reliable post-processing tool, which can provide objective quantitative analysis of metabolite concentration. Our purpose is evaluating accuracy of LCModel, while it analyzes amino acids spectrum by changing different linewidth of spectra and different level of noises. Lactate, cytosolic amino acids, alanine and acetate have been recognized as potential abscess markers, especially amino acids. In this thesis, we obtained the magnetic resonance spectra by GAVA simulation and then processed the concentration analysis on amino acids. However, some factors would disturb the analysis of in vivo proton MRS. In this study, we investigated the accuracy using LCModel to analyze amino acids spectrum. Firstly, we changed spectral linewidth by full width at half maximum (FWHM). Secondly, different levels of noises were added into those simulated spectra. Finally, we investigated how the FWHM spectral linewidth and signal noise affected the result of quantitative analysis and metabolite detection. The results shows that we are able to evaluate whether the analyzed-results is reliable or not, by finding the lower bound of signal to noise ratio in simulation. It also indicates that Lactate affected by the control variables the most, while amino acids affected the less. In this experiment, our goal is to find the criteria of reliable quantification with LCModel on detecting lactate, cytosolic amino acids, alanine and acetate, in order to contribute in clinical applications on abscesses patients.

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Adithya, Lakshmanna Y. „Ultrafast Raman Loss Spectroscopy (URLS) : Understanding Resonant Excitation Response And Linewidth Changes“. Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2505.

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Raman spectroscopy involves change in the polarizability of the molecular system on excitation and is based on scattering process. Spontaneous Raman scattering is a two photon process, in which the input light initiates the excitation, which then leads to an emission of another photon due to scattering. It is extensively used to understand molecular properties. As spontaneous Raman scattering is a weak process, the detection of these weak Raman photons are rather difficult. Alternatively, resonance Raman (RR) scattering is another technique where the excitation wavelength is chosen according to the material under study. The excitation wavelength is chosen to be within the absorption spectrum of the material under study. RR spectroscopy not only provides considerable improvement in the intensity of the Raman signal, but also provides mode specific information i.e. the modes which are Franck-Condon active in that transition can be observed. There are reports on RR studies of many systems using pulsed light as an excitation source. It is necessary to use at least two pulsed laser sources for carrying out the time resolved RR spectroscopy. A single pulse source for excitation would lead to compromise either with temporal or spectral resolution which is due to the uncertainty principle. If an excitation pulse has pulse width of ~100 femtoseconds then the spectral resolution will be ~ 150 cm-1. It is clear now that for improving the temporal and spectral resolution simultaneously, usage of single pulse for Raman experiments (spontaneous scattering) is not adequate. The usage of multiple laser pulses may provide the way out to improve the resolutions. Nonlinear spectroscopy in a broad view helps in understanding the structural and dynamical properties of the molecular systems in a deeper manner. There are a number of techniques as a part of nonlinear spectroscopy that have emerged in due course to meet different requirements and to overcome some difficulties while understanding the molecular properties. Stimulated Raman (SRS) gain, coherent anti-Stokes Raman scattering (CARS) and the inverse Raman spectroscopy are a few to mention as third order nonlinear spectroscopic techniques which give the similar kind of information about the molecular systems. Stimulated Raman scattering is a more general process involved in nonlinear Raman processes. SRS involves at least two laser pulses and the difference in their frequencies should match with the vibrational frequency of the molecule. The polarization has to be matched between the Raman pump and the Raman probe pulses. We have developed a new nonlinear Raman technique in our laboratory named as ultrafast Raman loss spectroscopy (URLS) using the principles of nonlinear Raman scattering. It involves the Raman pump (~ 1 picosecond (ps) or ~ 15 cm-1spectral resolution) and Raman probe as a white light continuum (100 fs) whose frequency components ranges from 400-900 nm. The laser system consists of Tsunami which is pumped by a Millennia laser and Spitfire-Pro, a regenerative amplifier which is pumped by an Empower laser. Tsunami provides a 100 fs, 780 nm centered, 80 MHz and ~6 nJ energy laser pulses. The Tsunami output is fed into Spitfire to amplify its energy and change the repetition rate to 1 KHz. The pulse length of the input pulse is preserved in amplification. The output of amplifier is split into two equal parts; one part is used to pump the Optical Parametric Amplifier (OPA) in order to generate wavelengths in the range 480-800 nm. The output of the OPA is utilized to generate Raman pump which has to be in ps in order to get the best spectral resolution. A small portion of the other part of amplifier output is utilized to generate white light source for the Raman probe. The remaining part of the amplifier output is used to pump TOPAS to generate wavelengths in the ultraviolet region. URLS has been applied to many molecular systems which range from non-fluorescent to highly fluorescent. URLS has been demonstrated to be very sensitive and useful while dealing with highly fluorescent systems. URLS is a unique technique due to its high sensitivity and the Raman loss signal intensity is at least 1.5-2 times higher as compared to the Raman gain signal intensities. Cresyl violet perchlorate (CVP) is a highly fluorescent system. URLS has been applied to study CVP even at resonance excitation. Rhodamine B has also been studied using URLS. Spontaneous Raman scattering is very difficult to observe experimentally in such high quantum yield fluorescent systems. The variation in the lineshapes of the Raman bands for different RP excitation wavelengths in URLS spectra shows the mode dependent behavior of the absorption spectrum. The experimental observation of variation in the lineshape has been accounted using theoretical formalism. The thesis is focused on discussing the development of the new nonlinear Raman spectroscopic technique URLS in detail and its applicability to molecular systems for better understanding. A theoretical formalism for accounting the uniqueness of URLS among the other nonlinear Raman techniques is developed and discussed in various pictorial representations i.e. ladder, Feynman and closed loop diagrams. A brief overview of nonlinear spectroscopy and nonlinear Raman spectroscopy is presented for demonstrating the difference between the URLS and the other nonlinear Raman techniques.

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Bücher zum Thema "Specral linewidth"

Potzick, James E. Antireflecting-chromium linewidth standard, SRM 473, for calibration of optical microscope linewidth measuring systems. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

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Vezzetti, Carol F. Antireflecting-chromium linewidth standard, SRM 475, for calibration of optical microscope linewidth measuring systems. Gaithersburg, MD: U.S. Dept. of Commerce, National Institute of Standards and Technology, 1992.

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Vezzetti, Carol F. Antireflecting-Chromium linewidth standard, SRM 475, for calibration of optical microscope linewidth measuring systems. Gaithersburg, Md: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1992.

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Buchteile zum Thema "Specral linewidth"

Harrison, J., und A. Mooradian. „Spectral Linewidth of Semiconductor Lasers“. In Methods of Laser Spectroscopy, 133–42. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4615-9459-8_19.

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Macfarlane, R. M. „Optical Spectral Linewidths in Solids“. In Lasers, Spectroscopy and New Ideas, 205–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-540-47872-0_14.

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Guilbaud, O., J. P. Goddet, S. Sebban, D. Joyeux, D. Ros, J. Gautier, K. Cassou et al. „Temporal Coherence and Spectral Linewidth of a Seeded Soft X-Ray Laser Pulse“. In Springer Proceedings in Physics, 193–98. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9924-3_22.

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Lopes, L. C., und B. Coqblin. „Linewidths in Neutron Scattering Spectra of Non-Cubic Cerium Kondo Compounds“. In Theoretical and Experimental Aspects of Valence Fluctuations and Heavy Fermions, 609–12. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4613-0947-5_102.

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Urbanski, L., M. C. Marconi, L. M. Meng, M. Berrill, O. Guilbaud, A. Klisnick und J. J. Rocca. „Spectral Linewidth Measurement of a Ne-Like Ar Capillary Discharge Soft X-Ray Laser“. In Springer Proceedings in Physics, 257–61. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-00696-3_41.

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Gentry, W. Ronald. „Interpretation of Linewidths in the Infrared Photodissociation Spectra of Van Der Waals Molecules“. In Structure and Dynamics of Weakly Bound Molecular Complexes, 467–75. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3969-1_32.

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Meng, L., A. Klisnick, M. Kozlova, K. Bohacek, M. Krus, J. Prokupek, L. Urbanski et al. „Temporal Coherence and Spectral Linewidth of Neon-Like XUV Lasers Pumped in the Quasi-steady State Regime“. In Springer Proceedings in Physics, 175–80. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-00696-3_28.

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Yahya, Mondher, Faouzi Hosni und Ahmed Hichem Hamzaoui. „Synthesis and ESR Study of Transition from Ferromagnetism to Superparamagnetism in La0.8Sr0.2MnO3 Nanomanganite“. In Smart Nanosystems for Biomedicine, Optoelectronics and Catalysis. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.89951.

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Electron spin resonance (ESR) spectroscopy was used to determine the magnetic state transitions of nanocrystalline La0.8Sr0.2MnO3 at room temperature, as a function of crystallite size. Ferromagnetic nanoparticles having an average crystallite size ranging from 9 to 57 nm are prepared by adopting the autocombustion method with two-step synthesis process. Significant changes of the ESR spectra parameters, such as the line shape, resonance field (Hr), g-factor, linewidth (∆Hpp), and the low-field microwave absorption (LFMA) signal, are indicative of the change in magnetic domain structures from superparamagnetism to single-domain and multi-domain ferromagnetism by increase in the crystallite size. Samples with crystallite sizes less than 24.5 nm are in a superparamagnetic state. Between 24.5 and 32 nm, they are formed by a single-domain ferromagnetic. The multi-domain state arises for higher sizes. In superparamagnetic region, the value of g-factor is practically constant suggesting that the magnetic core size is invariant with decreasing crystallite size. This contradictory observation with the core-shell model was explained by the phenomenon of phase separation that leads to the formation of a new magnetic state that we called multicore superparamagnetic state.

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Herbert, Bruce E., und Paul M. Bertsch. „A 19F and 2H NMR Spectroscopic Investigation of the Interaction Between Nonionic Organic Contaminants and Dissolved Humic Material“. In Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0009.

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Interaction between nonionic organic contaminants (NOC) and natural organic matter strongly influences the fate and transport of NOC in the environment. Microscopic descriptions of NOC-organic matter interaction have been developed based on macroscopic observations of NOC sorption to organic matter and organic solute transport under varying conditions. These models include the partitioning concept describing NOC sorption to organic matter and the concept of intra-organic matter diffusion used to account for nonequilibrium organic solute transport; however, little microscopic information exists to validate them. NMR may be a powerful method to gain information and insight concerning NOC-organic matter interaction. Chemical shifts, linewidths, and the magnitude of spin-spin couplings exhibited in the NMR spectra of a given nucleus are dependent on the characteristics of the surrounding media and therefore can be used to study the NOC-organic matter interaction. NMR characterization of the chemical interaction between NOC and organic matter can potentially provide information on important aspects of the sorption mechanism. This information may be useful to explain the influence of organic matter characteristics on NOC sorption and the mechanisms controlling nonequilibrium sorption of NOC to organic matter and mineral phases, and to evaluate different conceptual models of natural humic material, including the polymer concept, where humics are considered to be flexible linear polyelectrolytes, and the micelle concept, which considers humics to be aggregates of simple organic compounds, oligomers, and humic molecules ultimately forming micellar-type structures. NMR has been used to study the interactions of small organic solutes with macromolecules and organized organic assemblies. Fluorine-19 NMR has been particularly useful to study these interactions because this magnetically active nucleus is 100% abundant, has a high sensitivity (83% of 1H) and large chemical shift range, and exhibits no background signal. Several NMR studies have followed the interactions between fluorinated anesthetics and phospholipids, sodium dodecyl sulfate (SDS) micelles, and intact rabbit brain tissue. Generally, these studies have indicated both that sorption sites are less polar than aqueous solutions and that there is decreased mobility of the sorbed solute. Fluorine-19 NMR has also been used to characterize the interactions between fluorine-containing ligands, such as fluorotryptophan, and human serum albumin (HSA).

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Konferenzberichte zum Thema "Specral linewidth"

Shapiro, D. A. „Universal Scaling of Linewidth for Keilson—Storer Model“. In SPECTRAL LINE SHAPES. AIP, 2002. http://dx.doi.org/10.1063/1.1525479.

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Kawachi, Tetsuya. „Measurement of wavelength and linewidth of transient collisional x-ray lasers“. In SPECTRAL LINE SHAPES. AIP, 2002. http://dx.doi.org/10.1063/1.1525487.

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Röser, H. P. „Spectral linewidth of p-type Germanium laser“. In 15th International Conference on Infrared and Millimeter Waves. SPIE, 1990. http://dx.doi.org/10.1117/12.2301651.

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MATSUI, YASUSHI, JUN OHYA, MASATO ISHINO, HISANAO SATO, HIROYUKI SERIZAWA und TAKAO KAJIWARA. „Narrow spectral linewidth integrated-passive-cavity laser“. In Optical Fiber Communication Conference. Washington, D.C.: OSA, 1988. http://dx.doi.org/10.1364/ofc.1988.thk7.

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Spillman, Jr., W. B., D. R. Patriquin und B. R. Kline. „Spectral Linewidth Dependence of Photoelastic Sensor Performance“. In 29th Annual Technical Symposium. SPIE, 1986. http://dx.doi.org/10.1117/12.949779.

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Mawatari, Hiroyasu, Fumiyoshi Kano, Norio Yamamoto, Yasuhiro Kondo, Yuichi Tohmori und Yuzo Yoshikuni. „Spectral Linewidth and Linewidth Enhancement Factor in 1.5μm Modulation-Doped Strained MQW Lasers“. In 1993 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 1993. http://dx.doi.org/10.7567/ssdm.1993.d-7-1.

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Narducci, Lorenzo M., Christoph H. Keitel, Gian Luca Oppo und Marlan O. Scully. „Subnatural linewidth in large optical fields“. In Proceedings of the 12th International conference on spectral line shapes. AIP, 1995. http://dx.doi.org/10.1063/1.47506.

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Coleman, J. J., N. L. Dias und U. Reddy. „Narrow spectral linewidth surface grating DBR diode lasers“. In 2012 IEEE 23rd International Semiconductor Laser Conference (ISLC). IEEE, 2012. http://dx.doi.org/10.1109/islc.2012.6348390.

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MATSUI, Yasushi, Masato ISHINO, Toshihiro FUJITA und Hiroyuki SERIZAWA. „Optical Directional Coupler for Narrow Spectral Linewidth Light“. In 1985 Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 1985. http://dx.doi.org/10.7567/ssdm.1985.b-1-8.

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Deng Pan, Yaping Liu, A. E. Willner, Changjian Ke, Deming Liu und Songnian Fu. „Laser Spectral Linewidth Suppression Scheme for Coherent Detection“. In 39th European Conference and Exhibition on Optical Communication (ECOC 2013). Institution of Engineering and Technology, 2013. http://dx.doi.org/10.1049/cp.2013.1565.

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