Os autores gostariam de agradecer o apoio financeiro previsto para este estudo pela National Science Foundation (Grant n º: CMMI-0653578, CBET-0853890).

1. Configuração do sistema óptico (Fig. 1) <ol><li> Configurar uma placa de meia onda e um polarizador após a saída do laser para ajustar a energia de pulso de laser. </li><li> Configurar um divisor de feixe após o polarizador para dividir o pulso de laser de dois pulsos: pulso bomba e pulso sonda. </li><li> Use quatro espelhos que refletem e um palco manual de translação para a construção de um dispositivo de retardo óptico para o pulso da bomba. </li><li> Use outros espelhos quatro reflectoras para guiar o pulso de bomba para alcançar a superfície do alvo verticalmente. </li><li> Configurar um gerador de segunda harmónica (SHG) para transformar o laser de comprimento de onda de impulso a partir de 800 nm a 400 nm. </li><li> Usar um separador harmónica para transmitir o impulso de 800-nm e reflectem o pulso 400 nm. </li><li> Configurar um redutor de feixe e um par de lentes focalmente para ajustar o tamanho ea convergência do pulso sonda. </li><li> Configurar outro dispositivo atraso óptico, como mencionado no passo 1.3, para o pulso de sonda. </li><li> Use um anel Iris para ajustar a área dosonda de pulso e certifique-se o pulso de sonda passar a superfície do alvo na horizontal e se cruzam com a pulsação da bomba. </li><li> Configurar duas lentes objectivas e vários filtros para gerar a imagem da região de plasma a ser recebido pelo intensificada dispositivo de carga acoplada (ICCD) da câmara. </li><li> Ligue o computador, o laser, a câmera ICCD e seu controlador usando cabos BNC ou cabos USB. </li><li> Ajustar o tempo de atraso do controlador da câmara até a câmara capta uma imagem do pulso sonda. Assim, o pulso de sonda ea câmera estão sincronizados. </li></ol> 2. Bomba sonda-Sincronização <ol><li> Coloque um divisor de feixe na intersecção do pulso da bomba e do pulso da sonda, e criar dois fotodíodos para receber estes dois pulsos. Estes dois fotodíodos deve ter uma mesma distância a partir do divisor de feixe. </li><li> Use um osciloscópio para receber os sinais destes dois fotodíodos, e mover-se a fase de atraso no caminho do feixe bomba de pulsação até o próarquivos do pulso da bomba e do pulso sonda sobrepõem uns aos outros na tela osciloscópio. Uma precisão de 20 ps é conseguida devido à resolução temporal do osciloscópio. </li><li> Remover o divisor de feixe e os dois fotodíodos conforme mencionado na etapa 2,1. </li><li> Ajuste o estágio de atraso no caminho feixe de bombeio de pulso até a região de ruptura ar só poderia ser observado na tela ICCD. O momento em que a formação de repartição de ar pode ser detectado em vez de um fundo uniforme é determinada como zero tempo de atraso. </li></ol> 3. Amostra e Preparação Estágio <ol><li> Montou um laboratório-jack e dois manuais fases lineares, a fim de mover a amostra com três graus de liberdade. </li><li> Utilizar um indicador de marcação e calços de alta precisão para alcançar uma elevada planeza dos estágios. A diferença de altura deve estar dentro de 1 mM por uma distância de 25,4 mm. </li><li> Cortar uma peça quadrada (30 mm x 30 mm) a partir de uma folha de Cu com uma espessura de 0,8 mm utilizando um moagemmáquina. </li><li> Polir um lado estreito (30 mm x 0,8 mm) do pedaço de Cu até que a rugosidade da superfície é inferior a 0,5 micron. </li><li> Fixe o pedaço Cu no palco manual do topo com o rosto polido estreita para cima. </li><li> Mover o alvo por uma fase manual como mencionado na Etapa 3.1), enquanto controlar a sua posição através da câmara ICCD tal que qualquer inclinação pode ser ajustada através da inserção de calços de alta precisão abaixo do alvo. </li><li> Repita o passo 3,6 com a fase de outro manual. </li><li> Perfurar uma dúzia de furos no alvo enquanto variar a posição da lente focal por um estágio manual de alta precisão terceiro. A localização do ponto focal corresponde à posição da lente de contacto onde o menor orifício é perfurado. </li></ol> 4. Ablação e Mensuração <ol><li> Mover a lente focal até uma distância de cerca de 50 um de distância do ponto focal. </li><li> Mova o estágio atraso no caminho do feixe de pulso sonda com um intervalo de 0,3 mm para capturar a imagem todos os ps 2 até 10 ps, ​​oucom um intervalo de 3 mm para captar a imagem cada ps 20 até 480 ps. </li><li> Repita o passo 4,2 por várias vezes para repetibilidade e precisão. </li><li> Mova a lente focal para baixo a uma distância de cerca de 50 um de distância do ponto focal, e repita o passo 4.3. </li></ol> 5. Os resultados representativos As imagens radiografia medidos são mostrados na fig. 2 e fig. 3, para o ponto focal ligeiramente acima e abaixo da superfície do alvo, respectivamente. As posições de expansão longitudinal e radial são representados na figura. 4 e Fig.. 5. As expansões longitudinais destes dois casos no primeiro 100 ps são significativamente diferentes, no entanto, as suas expansões longitudinais na seguinte 400 ps e suas expansões radiais são semelhantes. Para o primeiro caso, o plasma dentro precoce 100 Ps tem uma estrutura de expansão unidimensional constituídas por várias camadas. Para o segundo caso, o pl precoceAsma tem uma estrutura de expansão bidimensional que não muda muito dentro de 100 ps. O modelo de simulação 12 é utilizado para investigar o mecanismo da evolução de plasma inicial. Tempo zero é definido como o momento em que o pulso de laser pico atinge a superfície do alvo. Os simulados processos evolutivos iniciais de plasma concorda bem com os resultados medidos para ambos estes dois casos, como mostrado na fig. 6 e Fig. 7, respectivamente. A formação do plasma precoce dentro de 1 ps também é previsto para o primeiro caso utilizando o modelo de simulação e mostrado na fig. 8. O plasma precoce é encontrado para ter uma região de ruptura de ar e uma região de plasma de Cu. A repartição ar é causada por multi-fotão de ionização e, em seguida, seguido por ionização avalanche. Para o segundo caso, no entanto, o ponto focal está abaixo da superfície do alvo e não região de ruptura de ar separado é formado. Em vez disso, a ionização do ar ocorre perto do pla Cusma frente e é causada pelo impacto de ionização devido aos elétrons livres ejetados do alvo Cu. <img alt="A Figura 1" src="/files/ftp_upload/4033/4033fig1.jpg" /> Figura 1. Esquemática da medição radiografia bomba sonda. <img alt="A Figura 2" src="/files/ftp_upload/4033/4033fig2.jpg" /> Figura 2. Cu expansão plasma em tempos de atraso sucessivas com o ponto focal ligeiramente acima da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo: Cu. <img alt="A Figura 3" src="/files/ftp_upload/4033/4033fig3.jpg" /> Figura 3. Cu expansão plasma em tempos de atraso sucessivas com o ponto focal ligeiramente abaixo da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo: Cu. &lt;img alt = &quot;Figura 4&quot; src = &quot;files/ftp_upload/4033/4033fig4.jpg /&quot; /&gt; Figura 4. Plasma longitudinal e as posições de expansão radial em tempos de atraso sucessivas com o ponto focal ligeiramente acima da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo: Cu. <img alt="A Figura 5" src="/files/ftp_upload/4033/4033fig5.jpg" /> Figura 5. Plasma longitudinal e as posições expansão radial em tempos de atraso sucessivas com o ponto focal ligeiramente abaixo da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo: Cu. Figura 6. Animação de expansão do plasma, medido e calculado dentro de um tempo de atraso de 70 ps com o ponto focal ligeiramente acima da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 </sup&gt; W / cm 2; alvo: Cu. <a href="http://www.jove.com/files/ftp_upload/4033/4033movie6.avi" target="_blank">Clique aqui para ver a animação</a> . Figura 7. Animação de expansão do plasma, medido e calculado dentro de um tempo de atraso de 70 ps com o ponto focal ligeiramente abaixo da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo: Cu. <a href="http://www.jove.com/files/ftp_upload/4033/4033movie7.avi" target="_blank">Clique aqui para ver a animação</a> . Figura 8. Animação de expansão do plasma, medido e calculado dentro de um tempo de atraso de 1 ps com o ponto focal ligeiramente acima da superfície. Comprimento de onda: 800 nm; duração de pulso: 100 fs; densidade de potência: 4,2 × 10 14 W / cm 2; alvo:. Cu <a href="http://www.jove.com/files/ftp_upload/4033/4033movie8.avi" target="_blank">Clique aqui para ver a animação &lt;</a>/ A&gt;.

<ol>
	<li>Garnov, S. V., Malyutin, A. A., Tsarkova, O. G., Konov, V. I., Dausinger, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+laser-induced+plasma+diagnostics+with+time-spatial+resolved+shadow+and+interferometric+techniques.">Ultrafast laser-induced plasma diagnostics with time-spatial resolved shadow and interferometric techniques.</a> Proc. SPIE. 4637, 31-42 (2002).</li><li>Zhang, N., Zhu, X., Yang, J., Wang, X., Wang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-resolved+shadowgraphs+of+material+ejection+in+intense+femtosecond+laser+ablation+of+aluminum.">Time-resolved shadowgraphs of material ejection in intense femtosecond laser ablation of aluminum.</a> Phys. Rev. Lett. 99, 167602 (2007).</li><li>Li, J., Wang, X., Chen, Z., Clinite, R., Mao, S. S., Zhu, P., Sheng, Z., Zhang, J., Cao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+electron+beam+imaging+of+femtosecond+laser-induced+plasma+dynamics.">Ultrafast electron beam imaging of femtosecond laser-induced plasma dynamics.</a> J. Appl. Phys. 107, 083305 (2010).</li><li>Veysman, M. E., Agranat, M. B., Andreev, N. E., Ashitkov, S. I., Fortov, V. E., Khishchenko, K. V., Kostenko, O. F., Levashov, P. R., Ovchinnikov, A. V., Sitnikov, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+optical+diagnostics+and+hydrodynamic+simulation+of+Ag+plasma+created+by+laser+irradiation+of+a+solid+target.">Femtosecond optical diagnostics and hydrodynamic simulation of Ag plasma created by laser irradiation of a solid target.</a> J. Phys. B. 41, 125704 (2008).</li><li>Geindre, J. P., Audebert, P., Rousse, A., Falli&#233;s, F., Gauthier, J. C., Mysyrowicz, A., Santos, A. D., Hamoniaux, G., Antonetti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency-domain+interferometer+for+measuring+the+phase+and+amplitude+of+a+femtosecond+pulse+probing+a+laser-produced+plasma.">Frequency-domain interferometer for measuring the phase and amplitude of a femtosecond pulse probing a laser-produced plasma.</a> Opt. Lett. 19, 1997-1999 (1994).</li><li>Inogamov, N. A., Anisimov, S. I., Petrov, Y. u. V., Khokhlov, V. A., Zhakhovskii, V. V., Nishihara, K., Agranat, M. B., Ashitkov, S. I., Komarov, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theoretical+and+experimental+study+of+hydrodynamics+of+metal+target+irradiated+by+ultrashort+laser+pulse.">Theoretical and experimental study of hydrodynamics of metal target irradiated by ultrashort laser pulse.</a> Proc. SPIE. 7005, 70052F.1-70052F.10 (2008).</li><li>Flacco, A., Guemnie-Tafo, A., Nuter, R., Veltcheva, M., Batani, D., Lefebvre, E., Malka, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+controlled+plasma+expansion+in+vacuum+for+laser+driven+ion+acceleration.">Characterization of a controlled plasma expansion in vacuum for laser driven ion acceleration.</a> J. Appl. Phys. 104, 103304.1-103304.5 (2008).</li><li>Mao, S. S., Mao, X., Greif, R., Russo, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simulation+of+a+picosecond+laser+ablation+plasma.">Simulation of a picosecond laser ablation plasma.</a> Appl. Phys. Lett. 76, 3370-3372 (2000).</li><li>Chen, Z., Mao, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+laser-induced+electronic+plasma+at+metal+surface.">Femtosecond laser-induced electronic plasma at metal surface.</a> Appl. Phys. Lett. 93, 051506.1-051506.3 (2008).</li><li>Kononenko, T. V., Konov, V. I., Garnov, S. V., Danielius, R., Piskarskas, A., Tamoshauskas, G., Dausinger, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+the+ablation+of+materials+by+femtosecond+and+pico-+or+nanosecond+laser+pulses.">Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses.</a> Quantum Electron. 29, 724-728 (1999).</li><li>Dausinger, F., Hügel, H., Konov, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro-machining+with+ultrashort+laser+pulses:+From+basic+understanding+to+technical+applications.">Micro-machining with ultrashort laser pulses: From basic understanding to technical applications.</a> Proc. SPIE. 5147, 106-115 (2003).</li><li>Hu, W., Shin, Y. C., King, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early-stage+plasma+dynamics+with+air+ionization+during+ultrashort+laser+ablation+of+metal.">Early-stage plasma dynamics with air ionization during ultrashort laser ablation of metal.</a> Phys. of Plasmas. 18, 093302.1-093302.12 (2011).</li></ol>

Não há conflitos de interesse declarados.

Os métodos de medição e de simulação apresentados neste trabalho permitem exames mais precisos da dinâmica do plasma precoce e um melhor entendimento dos mecanismos de ionização de ar e Cu. Estruturas de plasma de alta qualidade são capturados com uma resolução temporal de 1 ps e uma resolução espacial de 1 m. Esta medida tem uma alta repetibilidade também. O procedimento é crítica para alinhar o feixe muito bem e preparar uma superfície alvo com um achatamento elevada, bem como uma rugosidade baixa. Esta abordagem pode ser aplicada a outros materiais alvo e os parâmetros do laser diferentes. A única limitação do método radiografia bomba sonda é uma muito baixa variação de densidade de electrões número.

<table border="1"><tbody><tr><td> Nome do equipamento </td><td> Companhia </td><td> Número de catálogo </td></tr><tr><td> Laser </td><td> Spectra Physics- </td><td> SPTF-100F-1K-1P </td></tr><tr><td> Câmera ICCD </td><td> Princeton Instruments </td><td> 7467-0028 </td></tr><tr><td> Osciloscópio </td><td> Rigol </td><td> DS1302CA </td></tr><tr><td> Photodiode </td><td> Newport </td><td> 818-BB30 </td></tr><tr><td> Fase linear </td><td> Newport </td><td> 433 </td></tr><tr><td> Disque indicador </td><td> Mitutoyo </td><td> ID-C112E </td></tr></tbody></table>

investigation of early plasma evolution induced by ultrashort laser pulses

Plasmáticos iniciais é gerada devido à irradiação de alta intensidade do laser de alvo e da ionização de material subsequente alvo. Sua dinâmica desempenha um papel significativo na laser de material de interacção, especialmente no ambiente de ar 1-11. Evolução do plasma precoce tem sido capturado através de bomba de sonda-shadowgraphy 1-3 e interferometria 1,4-7. No entanto, as gamas de parâmetros estudados quadros de tempo e aplicado a laser são limitadas. Por exemplo, os exames directos de locais da frente de plasma e densidades número de electrões dentro de um tempo de atraso de 100 picossegundo (MA) com respeito ao pulso de laser de pico são ainda muito poucos, especialmente para o pulso ultracurtos com uma duração de cerca de 100 femtosegundo (FS) e uma densidade de potência baixo em torno de 10 14 W / cm 2. No início plasma gerado nestas condições só foi capturado recentemente, com alta resolução temporal e espacial de 12. A estratégia de configuração detalhada eprocedimentos do presente medição de alta precisão será ilustrado neste documento. A razão de ser da medição é shadowgraphy bomba sonda óptica: uma ultracurtos de laser de impulsos é dividido a um pulso de bomba e um pulso sonda, enquanto o tempo de atraso entre eles pode ser ajustado mudando os seus comprimentos caminho do feixe. O pulso bomba ablates o alvo e gera o plasma inicial, sendo o pulso sonda propaga através da região de plasma e detecta a não uniformidade da densidade número de electrões. Além disso, as animações são gerados utilizando os resultados calculados a partir do modelo de simulação de Ref. 12 para ilustrar a formação de plasma e evolução com uma resolução muito elevada (0,04 ~ 1 ps). Tanto o método experimental e do método de simulação pode ser aplicada a uma vasta gama de estruturas de tempo e os parâmetros do laser. Estes métodos podem ser usados ​​para examinar o plasma precoce gerado não só a partir de metais, mas também a partir de semicondutores e isoladores.

Watch this Scientific Journal Video about Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses at JoVE.com

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Um método experimental para examinar a evolução de plasma induzida por precoce ultracurtos impulsos laser é descrito. Usando este método, imagens de alta qualidade de plasma no início são obtidas com elevada resolução temporal e espacial. Um modelo integrado romance atomística é usado para simular e explicar os mecanismos de plasma inicial.

Investigação da Evolução Plasma Precoce Induzida por Pulsos ultracurtos de laser

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

investigation-early-plasma-evolution-induced-ultrashort-laser

Research

JoVE Journal

Engineering

14.8K visualizações.  Purdue University. Um método experimental para examinar a evolução de plasma induzida por precoce ultracurtos impulsos laser é descrito. Usando este método, imagens de alta qualidade de plasma no início são obtidas com elevada resolução temporal e espacial. Um modelo integrado romance atomística é usado para simular e explicar os mecanismos de plasma inicial.

Vídeo: Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Fabricação de Nano-engenharia transparentes Óxidos Realização por deposição por laser pulsado

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Engenharia

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1&#160;to 24 hr&#160;after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 &#956;m. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:&#160;elemental, molecular, or cellular.

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle&#039;s Mapping and Quantification in Organ Tissue

Laser-induced breakdown spectroscopy performed on thin organ and tumor tissue successfully detected natural elements and artificially injected gadolinium (Gd), issued from Gd-based nanoparticles. Images of chemical elements reached a resolution of 100 &#956;m and quantitative sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of a same biological tissue.

Induzida por laser Breakdown Spectroscopy: Uma Nova Abordagem para Mapeamento e Quantificação de nanopartículas em Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) ...

Laser-induced Forward Transfer for Flip-chip Packaging of Single Dies

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics industry. In this technique the chip and/or the substrate is bumped and the two are bonded via these conductive bumps. Many bumping techniques have been developed and intensively investigated since the introduction of the FC technology in 19601 such as stencil printing, stud bumping, evaporation and electroless/electroplating2. Despite the progress that these methods have made they all suffer from one or more than one drawbacks that need to be addressed such as cost, complex processing steps, high processing temperatures, manufacturing time and most importantly the lack of flexibility. In this paper, we demonstrate a simple and cost-effective laser-based bump forming technique known as Laser-induced Forward Transfer (LIFT)3. Using the LIFT technique a wide range of bump materials can be printed in a single-step with great flexibility, high speed and accuracy at RT. In addition, LIFT enables the bumping and bonding down to chip-scale, which is critical for fabricating ultra-miniature circuitry.

We demonstrate the use of the Laser-induced Forward Transfer (LIFT) technique for flip-chip assembly of optoelectronic components. This approach provides a simple, cost-effective, low-temperature, fast and flexible solution for fine-pitch bumping and bonding on chip-scale for achieving high-density circuits for optoelectronic applications.

Transferência para a frente induzida por laser para Flip-chip Embalagem de matrizes de solteiro

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

Seletiva Área Modificação de Superfície Wettability Silicon por Pulsed Laser irradiação UV em meio líquido

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

Como inflamar uma pressão atmosférica Microondas Plasma Torch sem qualquer Ignitores adicionais

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

Automação de Modo de bloqueio em uma rotação do laser da fibra não-linear de polarização através de medidas de polarização de saída

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

Transferência Atacante induzida por laser de Ag Nanopasta

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of &#39;high&#39; voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere.

Uma configuração Plasma Pressão atmosférica para investigar a formação de espécies reativas

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

Fabricação de 1-D cristal fotônico cavidade em um nanofibras com ablação induzida por laser femtosegundo

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

Localização de Defeitos Subsuperficiais por Aquecimento Estruturado usando a Termografia Fototérmica Projetada a Laser

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...