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Modern technologies depend on Rare-Earth elements, and they can be further improved using isotopic enriched/pure materials. This work brings the first successful attempt to enrich 163Dy by AVLIS (Atomic Vapor Laser Isotope Separation) in Brazil.

In this work, we report a newly observed isotope shift between 162Dy and 164Dy isotopes for the 0 → 16 717.79 cm−1 (598.003 nm) optical transition. We compared the newly observed results against two other lines (597.452 nm and 598.859 nm), which we measured in this work, and were already reported in the literature. The newly observed 162–164 Dy isotope shift, shows at least a 20% larger isotope shift than the isotope shifts for the other two lines investigated. The larger 162–164 isotope shift observed for the 598.003 nm line could lead to an increased isotope selectivity for atomic vapor laser isotope separation (AVLIS). Hence, this line could be a good choice for application in AVLIS. Experimental data available in the literature for the 597.452 nm and 598.859 nm lines, enabled us to perform simulations of spectra for both lines, in order to confirm the accuracy of our experimental measurements.

In this work we propose an experimental apparatus to investigate the isotope shift using two sub-Doppler techniques: Intermodulated Laser Induced Fluorescence and Intermodulated Optogalvanic Spectroscopy. The experimental set uses a portable hollow cathode lamp, which is an atomic source less expensive and simpler when compared to other techniques e.g. atomic beam. The method was applied to the erbium rare earth, being possible to observe the isotope shift for three transitions from the ground state: 0 → 17,347.860 cm−1 (576.440 nm), 0 → 17,157.307 cm−1 (582.842 nm) and 0 → 17,073.800 cm−1 (585.695 nm). The experimental erbium data from the literature were used to perform simulations of spectra in order to compare and confirm the accuracy of our measurements.

In this work, we suggest a methodology to determine the impact parameter for neutral dysprosium emission lines from the characterization of the plasma generated by laser ablation in a sealed chamber filled with argon. The procedure is a combination of known consistent spectroscopic methods for plasma temperature determination, electron density, and species concentration. With an electron density of 3.1 × 1018 cm–3 and temperature close to 104 K, we estimated the impact electron parameter for nine spectral lines of the neutral dysprosium atom. The gaps in the impact parameter data in the literature, mainly for heavy elements, stress the importance of the proposed method.

In this work, we report a newly observed isotope shift between

This paper presents the observation of the isotopes 162Dy, 163Dy and 164Dy of the optical transition 0→16717.79 cm−1 of the dysprosium. The high resolution spectrum was obtained through the laser induced fluorescence technique performed in an atomic vapor generated by laser ablation.

We present laser action in a single crystal fluoride fiber obtained by the micro-pulling-down technique. The 700 μm diameter and 1 cm long Nd:LiYF 4 fiber was pumped by a beam shaped diode bar emitting at 806 nm. A peak power of 300 mW was achieved with a slope efficiency of 12%. When considering the pump power fraction absorbed by the laser mode, a slope efficiency of 37% was achieved. To the best of our knowledge, this is the first report of a Nd: LiYF 4 fiber laser.

The effect of Yb" concentration on the frequency upconversion (UPC) of Er 3+ in PbO-GeO 2 -Ga 2 O 3 glasses is reported for the first time. Samples were prepared with 0.5 wt% of Er 2 O 3 and different concentrations of Yb 2 O 3 (1.0-5.0 wt%). The green (523 and 545 nm) and red (657 nm) emissions are observed under 980 nm diode laser excitation. The dependence of the frequency UPC emission intensity upon the excitation power was examined and the UPC mechanisms are discussed. An interesting characteristic of these glasses is the increase of the ratio of red to green emission, through an increase of the Yb 3+ concentration due to an efficient energy transfer from Yb 3+ to Er 3+ .

We report the infrared-to-visible frequency up- conversion in Er 3+ -Yb 3+ -codoped PbO-GeO2 glass con- taining silver nanoparticles (NPs). The optical excitation is made with a laser at 980 nm in resonance with the 2 F5/2 → 2 F7/2 transition of Yb 3+ ions. Intense emission bands cen- tered at 525, 550, and 662 nm were observed correspond- ing to Er 3+ transitions. The simultaneous influence of the Yb 3+ → Er 3+ energy transfer and the contribution of the in- tensified local field effect due to the silver NPs give origin to the enhancement of the whole frequency upconversion spec- tra.

The present work studies the production of super hydrophobic surfaces with laser ablation on Ti6Al4V. After a few hours of low pressure exposure, the textured surface showed a contact angle above 150°.

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

Here we report on the generation of ten deep blue to cyan laser emission lines using an intracavity frequency converted Raman laser. The fundamental laser field of the intracavity Raman laser is based on the 3 level transition of a Nd:YLF laser crystal, providing a short wavelength at 903 or 908 nm. When combined with generation of a Stokes shifted field via intracavity stimulated Raman scattering (SRS) by a KGW Raman crystal, enables generation of laser emission in the deep blue to cyan wavelength regime via additional nonlinear frequency conversion. Output at several blue-green wavelengths was achieved, with quasi continuous wave (qcw) output powers of up to 1W. A detailed study of the spectral behavior of the underlying Raman laser processes revealed strong spectral broadening of the fundamental laser line at 908 nm to a width of up to 4 nm. The effect of the spectral broadening on the overall laser efficiency is analyzed.

In this work we report the operation of the first diode-side-pumped continuous-wave (cw) self-Raman laser at 588 nm. The very cost-effective design allows for efficient stimulated Raman scattering using a grazing incidence configuration.

Here we report quasi-CW operation of intracavity Raman laser generating three blue laser emission lines at 454 nm, 473 nm and 495 nm with a maximum output power of 230 mW.

This is the first time that significant Stokes output power of 0.88 W at 990 nm has been achieved using a three-level fundamental transition (quasi-cw Nd:YLF laser) with stimulated Raman scattering in a KGW crystal.

We demonstrate a diode-side-pumped Nd:YVO4 self-Raman laser at 1176 nm in a grazing incidence configuration operating in quasi-continuous mode. More than 8 W of output power was achieved in multimode operation, corresponding to a slope efficiency of 15%. With TEM00 mode operation is also demonstrated.

1st Stokes laser emission is demonstrated at 994 nm by shifting the Neodymium 914 nm emission in a Nd:GdVO4 self-Raman laser. Competition between 914 nm and 961nm laser lines is observed and analyzed.

Nd:YLF laser at 908 nm, providing an QCW output power of 6.4 W at 33 W of absorbed pump power and a laser threshold of 3.2 W of absorbed pump power at 797 nm.

We compare, for the first time to the best of our knowledge, the behavior of a grazing incidence Nd:YVO4 laser when pumped at 808 nm and when directly pumped at 880 nm. We report a more linear behavior of the output power as a function of input power under direct pumping, due to a decrease in thermal effects.

Lasers operando nas regiões espectrais do azul e do amarelo-laranja foram recentemente requisitados pelo mercado de aplicações quer para melhorar as tecnologias já conhecidas ou para possibilitar a criação de novas. Isso é devido às propriedades destas regiões espectrais, com o azul trazendo características tais como fótons de alta energia e feixes limitados por difração menores, enquanto a faixa do amarelo-laranja é ainda uma região espectral difícil de se atingir e não foi totalmente acessada ou nem mesmo acessada por fontes de luz laser eficientes. Aplicações dos lasers azuis são encontradas em tecnologias de alta densidade de armazenamento, displays a laser, sistemas LIDAR, pinças ópticas e uma longa série de aplicações que exigem alta precisão. Os lasers amarelo-laranja também têm aplicações importantes, destacando-se aplicações em cirurgia oftalmológica a laser, em displays de cores reais e como estrela guia (excitando linhas de sódio na atmosfera). A investigação de lasers de quase três níveis e laser Raman de Nd:YLF foi realizada neste trabalho. A finalidade é de propor fontes laser de alta potência e eficientes emitindo no azul e no amarelo para suprir as aplicações. Eficiência e potências de saída da ordem de Watt foram demonstradas para um laser de Nd:YLF emitindo em 908 nm assim como no segundo harmônico em 454 nm. Além disso, lasers Raman de Nd:YLF/BaWO4 e Nd:YLF/KGW foram demonstrados atingindo alguns Watts de potência de saída em regime quasi-CW e CW, com boas qualidades de feixe (M2 2) e em oito comprimentos de onda diferentes: 1147 nm, 1163 nm, 1167 nm , 549 nm, 552 nm, 573 nm, 581 nm e nm 583. Por fim, uma luminescência azul originada em alguns cristais Raman, durante a oscilação Stokes, teve sua origem e seus efeitos colaterais para lasers (perdas e calor adicionais) minuciosamente caracterizados. Lasers operating in the blue and yellow-orange spectral regions are sought after by the applications market either to improve well known technologies or to enable new ones. Blue lasers bring features such as high energy photons and smaller diffraction limited beams, while the yellow-orange range is a hard to reach spectral region where there is a considerable shortage of efficient laser light sources. Applications of the blue lasers are found in high density storage technologies, laser displays, LIDAR systems, optical tweezers and a long range of high precision demanding applications. The yellow-orange lasers also have important applications, with highlights in ophthalmologic laser surgery (photocoagulation), in true color displays and as a guide star (exciting sodium lines in the atmosphere). The investigation of Nd:YLF quasi-three level lasers and Nd:YLF Raman lasers was further studied in this work in order to provide high power and efficient blue and yellow lasers sources. Demonstrations of efficient and multi-Watt operation of a 908 nm laser and its respective second harmonic laser at 454 nm are described. Also, Nd:YLF/BaWO4 and Nd:YLF/KGW Raman lasers were demonstrated reaching Watt levels in quasi-CW and CW regime with very good beam qualities (M2 2) at eight different wavelengths: 1147 nm, 1163 nm, 1167 nm, 549 nm, 552 nm, 573 nm, 581 nm and 583 nm. Finally, a blue luminescence originating in some Raman crystals, during Stokes oscillation, has been studied in considerable detail. Its origin and consequences for laser operation (extra loss and heat load) have been identified.

A Nd:YLF/KGW Raman laser has been investigated in this work. We have demonstrated CW output powers at six different wavelengths, 1147 nm (0.70 W), 1163 nm (0.95 W), 549 nm (0.65 W), 552 nm (1.90 W), 573 nm (0.60 W) and 581 nm (1.10 W), with higher peak powers achieved under quasi-CW operation. Raman conversion of the 1053 nm fundamental emission is reported for the first time, enabling two new wavelengths in crystalline Raman lasers, 549 nm and 552 nm. The weak thermal lensing associated with Nd:YLF has enabled to achieve good beam quality, M(2) ≤ 2.0, and stable operation in relatively long cavities.

In order to improve the crystalline Raman lasers performance, this work presents the characterization of the power extracted by a blue luminescence present in some of the Raman crystals, seen as probable source of loss.

We report the generation of a comb of emission wavelengths in the near-infrared, and wavelength-tunable emission at up to five discrete wavelengths in the visible between 534 nm and 572 nm by making use of cascaded stimulated Raman scattering in potassium titnyl phosphate in combination with Nd:GdVO 4 and Nd:YLF laser crystals.

1.5 W of 1st Stokes, 1167 nm, cw output power was produced using a Nd:YLF laser crystal associated to a BaWO 4 Raman crystal. The laser built provided a M2 of 1.51 and 1.43, vertical and horizontal, respectively. This high beam quality and Watt level power laser was built in a long cavity, demonstrating the advantages of Nd:YLF, which will ultimately enable low amplitude noise Raman lasers and allowing long length cavity geometries, such as “V” shape, for better conversion efficiencies. A preliminary result for a cw 583 nm laser has delivered 0.61 W of output power.

In this work we present continuous and quasi-continuous operation of Nd:YLF operating at 908 nm and frequency conversion to 454 nm using LBO and BiBO nonlinear crystals with different sizes.

Lasers de estado sólido bombeados por diodo têm suprido grande parte da demanda por lasers de alta potência, juntamente com uma boa qualidade de feixe, além de oferecer a geração de radiação laser na região do visível. Dentre esses lasers, destacam-se os lasers de fibra, capazes de atingir altíssimas potências mantendo a qualidade de feixe devido a sua forma especial, que confina a radiação por longas extensões de fibra. Nesse trabalho foi caracterizada a emissão de vidros teluretos dopados com Yb3+ emitindo no azul (efeito cooperativo 500 nm) e de vidros germanatos dopados com Er3+ e codopados com Yb3+, emitindo no verde e no vermelho. Esses dois materiais foram também caracterizados na forma de fibra. Além disso, foram caracterizadas as perdas de uma fibra de Nd:YLF e o ganho desta em duas configurações de bombeamento, lateral e longitudinal. Como resultados, as fibras de teluretos apresentaram emissões no azul centradas em 500 nm e as fibras de germanatos apresentaram um aumento das emissões no visível com a inserção de Yb3+ como sensibilizador, demonstrando emissões no vermelho mais intensas que no verde. Ambas as fibras apresentaram perfis semelhantes às de seus respectivos vidros volumétricos. A fibra de Nd:YLF apresentou um ganho superior as perdas, para a configuração longitudinal, caracterizando-se como um amplificador, sendo assim, existe uma grande possibilidade de ocorrer a ação laser dessa fibra em trabalhos futuros. Esse resultado seria inédito, uma vez que, aos nossos conhecimentos, nunca antes foi obtida uma ação laser com tal fibra. Diode pumped solid state lasers have supplied a large part of the search for high power lasers, with good beam quality, in addition, these lasers are useful for generation of visible laser radiation. Fiber lasers have the capacity to reach these high powers with a good beam quality, due to its special design which confines the radiation through long fiber lengths. In this work were characterized the emission of tellurite glasses and Yb3+ doped fibers, with a blue fluorescence around 500 nm (cooperative effect) and germanates doped with Er3+ and codoped with Yb3+, emitting green and red photons. Furthermore, losses and the gain of a Nd:YLF fiber were characterized, using two different setups, side pump and end pump. As a result, was obtained blue emission in tellurite fibers and an increase of visible emissions in germanate, both glass and fiber, by the use of Yb3+ ions as a sensitizer. For higher Yb3+ concentrations, these germanates got red intensities bigger than green ones. Both the glass fibers pulled, presented the same emission profile of that measured in its respective bulks. The Nd:YLF fiber demonstrated a gain higher than the losses, through end pump setup, characterizing as an amplifier, attesting the possibility for a laser action in future works. It will be a new result, which is unpublished until the present moment, according with our researches, a laser action with this kind of fiber has never been reported.

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

Here we report 10 laser emission lines in the attractive deep blue to cyan spectral region from an intracavity frequency doubled Raman laser. The fundamental laser field that drives the Raman laser is based on the three-level transition of Nd:YLF. A maximum extracted quasi-continuous wave (qcw) output power of 0.94 W is achieved in the deep blue to cyan spectral regime.

An intracavity Raman laser based on laser transition in Nd:YLF is reported. Quasi-continuous wave Stokes output power was observed at 990 and 976 nm, and up to 0.88 W of peak output power was obtained at 990 nm.

Neste trabalho, que teve como objetivo o estudo do uso de meio ativo com birrefringência termicamente induzida (BIT) de Nd:YAG em ressonadores dinamicamente estáveis, foi proposto o desenvolvimento de um ressonador dinamicamente estável em anel de alta potência com a utilização de módulos laser bombeados lateralmente por diodos comerciais e com compensação de BIT, obtendo-se 55,6 W de potência na operação em frequência única com saída polarizada no modo contínuo. Esta potência, é a maior para lasers em frequência única de Nd:YAG em um único ressonador. Um cristal de triborato de lítio (LBO) foi inserido no ressonador para melhorar as características espectrais do laser por mecanismos de perdas não lineares sendo verificada a supressão dos modos longitudinais adjacentes ao modo principal, com um único pico de frequência com largura de 29 MHz. Este laser foi construído utilizando-se módulos laser comerciais possibilitando a obtenção de um sistema laser de alta potência com saída em frequência única com um baixo custo. Foram obtidos também outros ressonadores lineares com os módulos: Um laser com alta qualidade de feixe e potência de saída de 30 W contínuos e linearmente polarizado com M2=1,08, com seu melhor fator de qualidade medido de 1,02 em 24,8 W, e utilizando-se dois módulos construiu-se um ressonador com e potência de saída de 76 W linearmente polarizados com M2=1,3 e 1,1 e 100,5 W de potência com M2=1,7 e 1,9 nas direções vertical e horizontal, respectivamente. As equações de Magni para os ressonadores dinamicamente estáveis lineares [1] foram aplicadas aos ressonadores com zonas conjuntas e novas expressões foram apresentadas. As equações para os ressonadores em anel de Silvestri et al. [2] foram aplicadas para os ressonadores em anel simétricos com um par de espelhos curvos e novas expressões foram apresentadas. Em especial, mostrou-se que a largura e a posição de seu intervalo de estabilidade podem ser ajustadas de maneira independente e contínua variandose apenas as distâncias do ressonador. In this work, which aimed to study the use of the active medium of Nd:YAG with thermally induced birefringence in dynamically stable resonators, it was proposed the development of a high power dynamically stable ring resonator using commercial side pumped laser modules by diodes and with birefringence compensation, obtaining 55.6 W of power in single frequency operation with polarized output in continuous mode. This power is the highest for single-frequency Nd:YAG lasers in a single resonator to our knowledge. A lithium triborate (LBO) crystal was inserted in the resonator to improve the spectral characteristics of the laser by means of non-linear losses mechanisms, with the suppression of longitudinal modes adjacent to the main mode being verified with a single frequency peak with 29 MHz width. This laser was built using commercial laser modules, making it possible to obtain a low-cost single-frequency high power laser system. Other linear resonators were also obtained with the modules: A continuous and linearly polarized laser with high beam quality and output power of 30 W with M2 = 1.08 was found, with measured quality factor of 1.02 at 24, 8 W, and using two modules, a resonator with 76 W linearly polarized output was built with M2=1.3 and 1.1 and 100.5 W of power with M2 = 1.7 and 1, 9 in vertical and horizontal directions, respectively. Magni\'s equations for dynamically stable linear resonators [1] were applied to resonators with joint zones and equations and new expressions were presented. The equations for ring resonators by Silvestri et al. [2] were applied to symmetric ring resonators with a pair of curved mirrors and new expressions were presented. In particular, it has been shown that the width and position of its stability range can be adjusted independently and continuously by varying only the distances from the resonator.

Filmes finos radioativos possuem aplicação direta no desenvolvimento de baterias betavoltaicas e alfavoltaicas. Sendo que, a principal vantagem dessas baterias nucleares é a sua durabilidade que pode variar de dezenas a até uma centena de anos, dependendo da meia-vida do radioisótopo utilizado. Nesse contexto, a Deposição por Laser Pulsado (PLD) apresenta-se como uma importante ferramenta. Um aspecto relevante de um sistema que utiliza essa técnica, é que os principais equipamentos ficam fora da câmara onde o material é processado. Logo, tal característica viabiliza o crescimento de filmes finos radioativos, pois possibilita o desenvolvimento de um arranjo onde a área contaminada, devido o processamento de um alvo radioativo, seja controlada. Dessa maneira, o presente trabalho aborda o desenvolvimento de um sistema PLD destinado ao crescimento de filmes finos radioativos. Assim, no que concerne à obtenção da câmara de vácuo e montagem das peças, o sistema foi em grande maioria projetado em um software CAD 3D. Posteriormente, as peças que estariam sujeitas à contaminação por material radioativo foram usinadas e também obtidas através de impressão 3D, sendo assim, de fácil reposição. Como no processo de ablação há a formação de material particulado, um filtro com capacidade para retenção de 99,95% de partículas com até 0,3 µm foi acoplado à câmara, para que o material radioativo não fosse disperso para o restante dos equipamentos de vácuo. O sistema foi então implementado e alvos de Cobre radioativo foram processados durante 60 min e 120 min, resultando em filmes finos radioativos com espessura média de (167,81 ± 3,67) nm e (313,47 ± 9,17) nm, respectivamente. Dessa forma, foi realizado um estudo acerca da dinâmica de contaminação do sistema, em que o filtro utilizado mostrou-se eficiente na retenção do material radioativo, possibilitando que a contaminação ficasse retida na câmara de vácuo. Portanto, demonstra-se pela primeira vez a viabilidade da utilização da técnica PLD no crescimento de filmes finos radioativos, sendo então, possível a utilização desta em estudos futuros acerca do desenvolvimento de baterias nucleares betavoltaicas e alfavoltaicas. Radioactive thin films have a direct application in the development of beta-voltaic and alpha-voltaic batteries. The main advantage of these nuclear batteries is their durability, which can range from tens to a hundred years, depending on the half-life of the radioisotope used. In this context, Pulsed Laser Deposition (PLD) is an important tool. A relevant aspect of a system using this technique is that the main equipment is outside the chamber where the material is processed. Consequently, this feature allows the growth of radioactive thin films, as it enables the development of an arrangement where the contaminated area is controlled. In this way, the present work proposed the development of a PLD system for the growth of radioactive thin films. Thereby, regarding obtaining the vacuum chamber and the assembling of the parts, the system was mostly designed using 3D CAD software. Subsequently, the parts that would be subject to radioactive material contamination were obtained through machining and 3D printing, in this way they are easily replaceable. As the ablation process produces particulate material, a filter with a 99.95% holding capacity for particles with up to 0.3 µm was coupled to the chamber, so the radioactive material could not be dispersed to the remaining vacuum equipment. The PLD system was then implemented and radioactive copper targets were processed for 60 min and 120 min, resulting in radioactive thin films with an average thickness of (167.81 ± 3.67) nm and (313.47 ± 9.17) nm, respectively. Then, a study was performed about the contamination dynamics of the system, in which the filter used was efficient in retaining the radioactive material, allowing the contamination to be retained in the vacuum chamber. Thus, it is demonstrated for the first time the feasibility of using the PLD technique in the growth of radioactive thin films, being possible its use in future studies about the development of beta-voltaic and alpha-voltaic nuclear batteries.

O protótipo de um detector de nêutrons térmicos portátil foi desenvolvido no Instituto de Pesquisa Energéticas e Nucleares (IPEN-CNEN/SP), utilizando um fotodiodo de Si do tipo PIN associado a um filme de boro enriquecido. O filme de boro foi fabricado por meio da técnica de Deposição a Laser Pulsado, considerando duas possibilidades para depositar o boro: deposição direta do boro na face do fotodiodo e deposição na lâmina de vidro. Foram desenvolvidos dois protótipos, no primeiro foi possível ler apenas o sinal elétrico do sistema fotodiodo-boro no qual o filme está depositado na lâmina de vidro. Para aprimorar a resposta do sistema de detecção, outro circuito foi desenvolvido e permitiu contar nêutrons em ambas as situações tanto do filme na lamínula quanto do filme direto no fotodiodo. A caracterização dos protótipos foi feita via irradiação de feixes de nêutrons predominantemente térmicos e frios, por meio de quatro experimentos principais: reposta do sistema ao fluxo de nêutrons, teste de linearidade, resposta angular e o teste de reprodutibilidade. Os protótipos apresentaram uma resposta linear à variação do fluxo, reprodutibilidade, e a resposta angular não foi isotrópica. A eficiência intrínseca em porcentagem do protótipo 1 para um espectro de nêutrons predominantemente térmicos e frios foi (1,17 ± 0,01) % e (1,37 ± 0,01) %, respectivamente. No protótipo 2 foram feitas medições de nêutrons com os dois sistemas fotodiodo-boro (lâmina de vidro, direto no fotodiodo), porém nas medidas com o boro direto no sensor houve um aumento significativo no ruído eletrônico. A eficiência intrínseca do protótipo 2 para os nêutrons frios foi de (5,2 ± 0,4) %. A portable thermal neutron detector prototype, using a silicon photodiode type PIN coupled to a boron converter, was developed at Nuclear and Energy Research Institute (IPEN-CNEN/SP). The boron layers were made by Pulsed Laser Deposition method using two configurations: directly deposited on the surface of photodiode and at a glass surface. Two prototypes were made in this study using two different associated electronics, in the first prototype is only possible reads signs from the photodiode coupled to boron film and in the second one reads both types of configurations (directly on the photodiode, boron glass). The prototypes were characterized using thermal and cold neutron beam. Four experiments were performed: response of the detection system at neutron beam, linearity test, angular response and repetitive test. The prototypes present a linear behavior, were reproducible and the angular response of the prototypes was not isotropic. The values of intrinsic efficiency from the prototype 1 for thermal and cold neutron were respectively: (1.17 ± 0.01) % e (1.37 ± 0.01) %. In the prototype 2 it was performed an experiment for compare the read out in the detection system for the two possible configuration of system photodiode-boron, in the situation that the boron is part integrant of the system there was an significant increase in the electronic noise, therefore the characterization of this prototype were made using the boron film coupled to the photodiode, and intrinsic efficiency for cold neutron beam was (5.2 ± 0.4) %.

Lasers amarelos são de grande interesse devido ao seu potencial de aplicação na área médica. Uma das principais aplicações ocorre no tratamento de doenças retinianas, onde a radiação amarela apresenta bons resultados clínicos com o mínimo de efeitos colaterais. Apesar dos avanços no desenvolvimento de lasers com comprimento de onda amarelo, todas as alternativas existentes possuem limitações principalmente com relação à custo e à escolha do comprimento de onda. Este trabalho foi desenvolvido com o objetivo de apresentar uma alternativa às opções existentes. Para isto foi empregado um sistema de bombeio lateral por diodo de um cristal de Nd3+:YLiF4 (Nd:YLF) empregando o ângulo de Brewster para obtenção de um laser com comprimento de onda fundamental em 1053 nm. Para a conversão Stokes do comprimento de onda fundamental foi utilizado um cristal de KGd(WO4)2 (KGW) em configuração intracavidade, gerando as emissões Raman em 1147 nm e 1163 nm através dos deslocamentos de Stokes principais de 768 cm-1 e 901 cm-1. Conjuntamente foi utilizado um cristal de LBO (LiB3O5), também intracavidade, que por meio do fenômeno de geração de segundo harmônico (SHG) converte o comprimento de onda Raman em laser amarelo, gerando o comprimento de onda de 573 nm com potência máxima de saída de 6,06 W e com eficiência óptica de conversão diodo-SHG de 12%. São apresentados também resultados para um laser Raman intrínseco de Yb:KGW operando em 1096 nm na conversão Stokes de 89 cm-1. Foram obtidas eficiência de inclinação e eficiência óptica diodo-Raman de 42 % e 33,2%, respectivamente. Yellow lasers are of significant interest because of their potential in application in the medical field. One of the main applications occurs in the treatment of retinal diseases, where yellow radiation presents good clinical results with minimal side effects. Despite advances in the development of yellow wavelength lasers, all existing alternatives have limitations, especially with regard to cost and wavelength choice. This work was developed with the objective of presenting an alternative to the existing options. For this, a side-pumping of a Nd3+:YLiF4 (Nd:YLF) crystal was employed through Brewster angle obtaining a fundamental laser at 1053 nm. For the Stokes conversion of the fundamental laser, a KGd(WO4)2 (KGW) crystal was used in intracavity configuration, generating the Raman emissions at 1147 nm and 1163 nm, accessed by the two main Stokes conversion lines, 768 cm-1 e 901 cm-1. Together, an intracavity LBO (LiB3O5) crystal was used, which through second harmonic generation (SHG) phenomenon converts the Raman wavelength to a yellow laser, generating the wavelength of 573 nm with maximum output power of 6.06 W and diode-SHG conversion efficiency of 12%. Results are also presented for an Yb:KGW self-Raman laser operating at 1096 nm on the 89 cm-1 Stokes conversion. Were obtained slope efficiency and diode-Raman conversion efficiency of 42% and 33,2%, respectively.

Lasers Raman são dispositivos que proporcionam uma maneira prática de transformar comprimentos de onda fundamentais em novas linhas espectrais via Espalhamento Raman Estimulado (Stimulated Raman Scattering - SRS). Quando combinados com outros processos de conversão não lineares, os lasers Raman fornecem acesso a comprimentos de onda na região do visível no espectro eletromagnético, que de outra maneira seriam de difícil acesso, como o laranja-amarelo, verde-limão e diversas linhas no azul. A grande vantagem dos lasers Raman é a possibilidade de geração de múltiplas frequências a partir de uma mesma combinação de cristais, tornando esse tipo de laser dispositivos baratos e compactos quando comparados a tecnologias como OPO. Neste trabalho um cristal de Nd:YVO4 foi bombeado por diodo, em configuração transversal, sendo o cristal o responsável pela emissão laser e pelo espalhamento Raman. Na primeira parte do trabalho, a cavidade utilizada apresentava alto fator de qualidade para o comprimento de onda fundamental (1064 nm) e foi estudada a operação laser do 1º Stokes (1176 nm) em regimes de operação quase contínua (q-cw) e contínua (cw). Foi explorada a configuração com uma dobra do feixe laser em ângulo rasante na superfície de bombeamento, bem como a configuração com duas dobras nesta mesma superfície (double beam mode controlling - DBMC). Na segunda parte do trabalho, um cristal LBO foi utilizado para a geração do segundo harmônico (SHG) em 588 nm, o que corresponde a um laser laranja-amarelo. Foi utilizada a configuração com uma dobra e operação cw,com a qual a cavidade apresentava alto fator de qualidade tanto para o 1064 nm quanto 1176 nm. Com a configuração de uma dobra, foi demonstrado que o laser Raman opera em multimodo, com uma variedade de modos de Hermite-Gauss que puderam ser selecionados através apenas do alinhamento da cavidade, incluindo o modo TEM00. Com configuração DBMC, o laser apresentou operação estável oscilando o modo TEM00. Em 1176 nm em regime q-cw, foi obtida a potência máxima de 8,2 W por pulso (multimodo) e 11,7% de eficiência óptica de conversão (diodo para o 1º Stokes), e operando em modo TEM00 a potência máxima de 3,7 W por pulso e eficiência de 5,4% foi obtida com a configuração de duas dobras, de maneira que a tecnologia DBMC se mostrou eficiente para geração de um laser robusto e estável operando com o modo TEM00. Em regime cw o melhor resultado em termos de potência e eficiência foi obtido com a configuração de uma dobra, correspondendo a 1,8 W e 7,3% de eficiência com o laser operando em multimodo. Com o laser laranja, foi demonstrada a operação do modo TEM00 para potências de bombeamento abaixo de 14,5 W. A potência máxima obtida em multimodo foi 820 mW correspondendo a 4% de eficiência óptica de conversão. Raman lasers are devices that provide practical means to shift fundamental laser wavelengths into new spectral lines via Stimulated Raman Scattering (SRS). When combined with other nonlinear conversion processes, Raman lasers permit access to hard-to-reach regions of the visible electromagnetic spectrum, for example, orange-yellow, lime-green and several blue lines. The great advantage of Raman lasers is the possibility of generating multiple wavelengths using the same set of crystals, which make these devices compact and practical when compared to other technologies as OPOs. In this work, the Nd:YVO4 crystal was laterally pumped by a diode laser and this crystal was responsible for laser generation as well as SRS. In the first part of this work, the laser cavity presented a high Q factor for the fundamental laser wavelength (1064 nm) and the laser operation at the first Stokes (1176 nm) was characterized under quasi-continuous wave operation (q-cw) and in continuous wave (cw) operation. The grazing incidence geometry of the cavity with a single bounce of the laser beam at the pumped facet of the crystal was exploited, as well as with the double bounce (double beam mode controlling - DBMC) of the laser beam at this same crystal facet. In the second part of this work, a LBO crystal was utilized for the second harmonic generation (SHG) at 588 nm, which corresponds to an orange-yellow laser. The single bounce cavity configuration was utilized under cw operation, which presented high Q factor at 1176 nm and at 1064 nm. With the single bounce configuration, the laser operated in a variety of Hermite- Gaussian transversal modes that could be selected simply by cavity alignment, including the TEM00 mode. With the DBMC technology, the laser presented stable operation of the TEM00 mode. At 1176 nm, under q-cw regime, the maximum output peak power of 8.2 W (multimode) was achieved, corresponding to an optical conversion efficiency (diode to 1st Stokes) of 11.7%, and operation of the TEM00 mode yielded a maximum output peak power of 3.7 W and 5.4% efficiency with the double bounce configuration, hence the DBMC technology showed to be an efficient method for the generation of a stable and robust laser operating with TEM00 mode. Under cw regime, the best result in terms of power and efficiency was obtained with the single bounce geometry, yielding 1.8 W (multimode) corresponding to 7.3% efficiency. For the orange-yellow laser, operation of the TEM00 laser mode was demonstrated for low pump powers up to 14.5 W. The maximum output power achieved in multimode operation was 820 mW and 4% optical conversion efficiency.