111 |
Laser decontamination and cleaning of metal surfaces : modelling and experimental studies / Décontamination et nettoyage laser appliqués aux surfaces métalliques : études théorétiques et expérimentalesLeontyev, Anton 08 November 2011 (has links)
Le nettoyage des surfaces métalliques est nécessaire dans différents domaines de l'industrie moderne. L'industrie nucléaire cherche de nouvelles méthodes de décontamination des surfaces oxydées, et les installations thermonucléaires nécessitent le nettoyage des composants face au plasma pour enlever la couche déposée contenant tritium. L'ablation laser est proposée comme une méthode efficace et sûre pour le nettoyage des surfaces métalliques et leur décontamination. Le facteur important influençant le chauffage et l'ablation laser est la distribution en profondeur de l’intensité laser. Le modèle de propagation de la lumière dans une couche diffusant sur un substrat métallique est développé et appliqué pour analyser les caractéristiques de distribution de lumière. Pour simuler les surfaces contaminées, l'inox AISI 304L a été oxydé par laser et chauffé dans un four. La contamination radioactive de la couche d'oxyde a été simulée par l'introduction d’europium et / ou de sodium. Un facteur de décontamination de plus de 300 a été démontré avec le régime de nettoyage optimal trouvé. Une diminution de la résistance à la corrosion a aussi été montrée après un nettoyage laser. Les seuils d'ablation des surfaces ITER-like (représentatives d’ITER) ont été mesurés. Une vitesse de nettoyage de 0,07 m2/W∙h a été trouvée. Pour les surfaces miroir, les seuils de dommages étaient déterminés pour éviter les dommages lors du nettoyage au laser. La possibilité de restaurer la réflectivité après le dépôt d’une couche mince de carbone a été démontrée. Les perspectives de développement ultérieur de nettoyage laser sont discutées. / Metal surface cleaning is highly required in different fields of modern industry. Nuclear industry seeks for new methods for oxidized surface decontamination, and thermonuclear installations require the cleaning of plasma facing components from tritium-containing deposited layer. The laser ablation is proposed as an effective and safe method for metal surface cleaning and decontamination. The important factor influencing the laser heating and ablation is the in-depth distribution of laser radiation. The model of light propagation in a scattering layer on a metal substrate is developed and applied to analyse the features of light distribution. To simulate the contaminated surfaces, the stainless steel AISI 304L was oxidized by laser and in a furnace. Radioactive contamination of the oxide layer was simulated by introducing europium and/or sodium. The decontamination factor of more than 300 was demonstrated with found optimal cleaning regime. The decreasing of the corrosion resistance was found after laser cleaning. The ablation thresholds of ITER-like surfaces were measured. The cleaning productivity of 0.07 m2/hour∙W was found. For mirror surfaces, the damage thresholds were determined to avoid damage during laser cleaning. The possibility to restore reflectivity after thin carbon layer deposition was demonstrated. The perspectives of further development of laser cleaning are discussed.
|
112 |
波長可変フェムト秒ファイバレーザーを用いたプラズマ励起表面反応の動的計測法の構築後藤, 俊夫, 堀, 勝, 西澤, 典彦 03 1900 (has links)
科学研究費補助金 研究種目:基盤研究(A)(2) 課題番号:15206012 研究代表者:後藤 俊夫 研究期間:2003-2004年度
|
113 |
Estudo das propriedades ópticas do grafeno e sua aplicação como absorvedor saturável em lasers à fibra dopada com érbioRosa, Henrique Guimarães 25 February 2015 (has links)
Made available in DSpace on 2016-03-15T19:38:52Z (GMT). No. of bitstreams: 1
Henrique Guimaraes Rosa.pdf: 6486656 bytes, checksum: 6fc9fe7875ed2cceb89c9f5179b9f028 (MD5)
Previous issue date: 2015-02-25 / Fundo Mackenzie de Pesquisa / In this thesis, we present results on the fabrication, transfer and characterization of
chemical vapor deposition (CVD) graphene and exfoliated graphene over glass and optical
fiber substrates, to study optical properties of graphene and its application as a saturable
absorber for Erbium-doped fiber laser (EDFL). Monolayer CVD graphene and stacked CVD
graphene samples were fabricated and characterized, transferred to the transverse face of
optical fibers, and a study on the relation between the optical properties of graphene samples
and the properties of ultrashort laser pulses generated in (EDFL) was performed. Furthermore,
we have developed a technique for transferring exfoliated nanomaterials which allowed us to
transfer exfoliated graphene onto optical fiber s faces and align the graphene flake to the fiber
core. With this transfer technique it is possible to fabricate samples with controlled number of
graphene layers onto optical fiber faces. As application, we demonstrate ultrashort pulse
generation in Erbium-doped fiber laser with exfoliated monolayer graphene samples as
saturable absorber. This is the first time that ultrashort laser pulses are generated with a single
exfoliated monolayer graphene sample. / Nesta tese, apresentamos resultados sobre a fabricação, transferência e caracterização
de grafeno CVD (grafeno fabricado por deposição química de vapor chemical vapour
deposition) e de grafeno esfoliado em substratos de vidro e em fibras ópticas, para o estudo
das propriedades ópticas do grafeno e sua aplicação como absorvedor saturável em laser à
fibra dopada com Érbio (EDFL). Foram fabricadas e caracterizadas amostras de grafeno CVD
monocamada e de grafeno CVD empilhado, transferidas para a face transversal de fibras
ópticas, e com estas amostras foram feitos estudos sobre a relação entre as propriedades
ópticas do grafeno e as propriedades de pulsos ultracurtos gerados em EDFL. Além disto,
desenvolvemos uma técnica para a transferência de nanomateriais esfoliados que permitiu a
transferência de grafeno esfoliado para fibras ópticas e seu alinhamento com o núcleo da
fibra. Com esta técnica de transferência é possível fabricar amostras com controlado número
de camadas de grafeno em fibra óptica. Como aplicação, demonstramos a geração de pulsos
em EDFL com uma amostra de grafeno esfoliado monocamada como absorvedor saturável.
Esta é a primeira vez que pulsos ultracurtos são gerados em lasers à fibra com amostra de
grafeno esfoliado de uma única camada sobre a face transversal da fibra óptica.
|
114 |
Vliv dlouhých optovláknových tras na polarizační stav světla a jejich využití pro napájení polarizačních senzorů / Long optical fibre routes influence on the polarizing state of light and uses it for powering polarization sensorsPanascí, Marco January 2021 (has links)
This diploma thesis deals with the influence of long fiber optic paths on the polarization state of light and their use for powering polarization sensors. The aim of the diploma thesis was to design the arrangement of optical fiber components so that the polarization properties of light at the end of the path are further usable for sensory purposes. Four partial measurements with a long path (in a laboratory setting, laying in the ground, on a curtain, under the influence of external influence) and one measurement without a path under the influence of external influence were designed. The overall measurement results demonstrate that for the functional power supply of long-distance sensor systems, an existing single-mode fiber can be used (laid by laying in the ground), into which a light source for a given sensor system would be multiplexed. In the discussion, all types of measurements are analyzed and compared with each other. Finally, the overall result is summarized and applications are described in which such a sensor system could be used.
|
115 |
[pt] LASERS DE FIBRA DE MODO TRAVADO PARA REFLECTOMETRIA ÓPTICA NO DOMÍNIO DO TEMPO E SENSORIAMENTO / [en] MODE-LOCKED FIBER LASERS FOR OPTICAL TIME-DOMAIN REFLECTOMETRY AND SENSINGMARLON MEDEIROS CORREIA 16 May 2023 (has links)
[pt] Diferentes tipos de lasers podem ser usados para gerar pulsos de luz com
uma ampla faixa de durações de pulso, energias e potências de pico. As técnicas
de Q-switching e mode-locked são relatadas há anos por vários autores e
pesquisadores e são frequentemente utilizadas na geração de lasers de pulso
ultracurto com duração de pulso no domínio do tempo na faixa de nanossegundos
até femtossegundos. Uma configuração, com ganho fornecido por um
amplificador óptico semicondutor (SOA) e amplificador de fibra dopada com
érbio (EDFA) é proposta e emprega a técnica de gerenciamento de dispersão para
gerar um trem de pulsos ópticos exibindo alta potência de pico, taxa de repetição
ultra-baixa e largura temporal curta, habilitando que este laser seja usado como
uma fonte para aplicações de alta resolução em reflectometria óptica no domínio
do tempo (OTDR). A operação mode-locked é conhecida por ocorrer apenas em
lasers ordenados padrão por um longo tempo e até recentemente foi encontrado
também em lasers de fibra aleatórios desordenados (RFL). Embora tenha havido
progresso no sentido de travar modos espaciais e longitudinais em lasers
aleatórios, a literatura carece de relatos sobre geração de pulsos limitada por
transformada de Fourier, apesar das muitas décadas de campo. O autor demonstra
experimentalmente um mode-locked random fiber laser (MLRFL) operando como
um refletômetro óptico de domínio do tempo sensível à fase. Aqui, a
saída total do laser fornece o sinal de detecção, em contraste com o pequeno sinal
retroespalhado medido em um OTDR convencional. O laser opera como um
sensor acústico distribuído (DAS) e sensor de temperatura distribuído (DTS). / [en] Different types of lasers can be used to generate light pulses with a wide
range of pulse durations, energies and peak powers. Q-switching and mode-locked
techniques have been reported for years by several authors and researchers and are
frequently used in the generation of ultra-short-pulse lasers with time-domain
pulse durations from the nanosecond to femtosecond range. A configuration, with
gain provided by a semiconductor optical amplifier (SOA) and erbium-doped
fiber amplifier (EDFA) is proposed and employ the dispersion management
technique to generate a train of optical pulses exhibiting high-peak-power, ultralow repetition rate, and fast temporal width, enabling this laser to be used as a
source for high-resolution optical time domain reflectometer (OTDR)
applications. The mode-locking operation has been known to occur only in
standard ordered lasers for a long time and until recently it was found to also
occur in disordered random fiber lasers (RFL). Although progress has been made
towards locking spatial and longitudinal modes in random lasers, the literature
lacks reports on Fourier transform-limited pulse generation despite the many
decades of the field. The author experimentally demonstrates a mode-locked
random fiber laser (MLRFL) operating as a lasing phase-sensitive optical time domain reflectometer based on random feedback from a sensing fiber.
Here, the full output of the laser provides the sensing signal, in contrast to the
small backscattered signal measured in a conventional OTDR. The laser operates
as a distributed acoustic sensor (DAS) and distributed temperature sensor (DTS).
|
Page generated in 0.349 seconds