Name: stimulated stokes and antistokes raman scattering in microspherical whispering gallery mode resonators
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Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi
Ente Cassa di Risparmio di Firenze (No. 2014.0770A2202.8861)

1. Fabricação de Ultra Fator de Microesferas de qualidade <ol><li> Tira cerca de 1-2 cm de um modo único (SMF) de fibra de sílica padrão fora de seu revestimento acrílico usando uma stripper de óptica. </li><li> Limpe a parte descascada com acetona e pegará-lo. </li><li> Introduzir a ponta clivada em um braço de um splicer de fusão e produzir uma série de descargas de arco elétrico, utilizando o controlador splicer. Selecione &quot;operação manual&quot; no menu controlador splicer, defina os valores para o nível de potência do arco e arco duração de 60 e 800 ms, respectivamente; selecione &quot;arco&quot; e empurre a parte inferior &quot;+&quot;. </li><li> Uma vez que uma esfera está tomando forma, parar, girar a fibra em 90 ° e repita o passo 1.3. </li><li> Repetir o passo 1.3, pelo menos 4 vezes para obter uma microesfera de cerca de 160 um. Repetir 16 vezes para se obter uma microesfera de cerca de 260 uM. Nota: As descargas de arco eléctrico irá produzir a temperatura de fusão elevada necessária para fundir o vidro de sílica. o surface tensão vai chamar um esferóide a partir da ponta da fibra amolecidas; o tamanho das esferas é directamente proporcional ao número de disparos de arco, saturando com um diâmetro de cerca de 350 um, como pode ser visto na Figura 1 19. A rotação assegura uma forma esférica do dispositivo de ressonância. </li></ol> 2. Desenho de um Fiber Tapered Nota: A fibra cónica, também é necessário para o acoplamento de luz para os microresonators. O tamanho da microesfera vai determinar a cintura do cone. Para esfera diâmetros maiores que 125 um, o diâmetro do cone pode ser de cerca de 3-4 um. Por menores, o diâmetro do cone deve ser menor, digamos 1-2 uM. A fim de manter as perdas em baixo nível e a ter apenas um modo de na secção cónica (o fundamental), o afunilamento deve ser adiabática (transição gradual de espessura e diâmetro fino). O comprimento total típica da secção cónica adiabático é de cerca de 2 cm. FiguRE 2 mostra o dispositivo caseira para puxar a fibra e A Figura 3A mostra uma microfotografia de uma zona de cintura típico. <ol><li> Faixa de 3-4 cm de um modo único (SMF) de fibra de sílica padrão fora de seu revestimento acrílico usando uma stripper de óptica, e ligar as extremidades da fibra a um laser (entrada) e um medidor de potência (saída). Certifique-se de que a zona descascada é aproximadamente no meio da fibra, não numa das extremidades. Usar um terminador de fibra nua, a fim de ser capaz de ligar as extremidades das fibras para o medidor de energia laser e. Coloque o laser e o medidor de energia na parte superior da bancada de trabalho. </li><li> Coloque a fibra despojado dentro de um pequeno cilindro de alumina, e as pontas revestidas da fibra em duas fases de tradução que actuam simultaneamente durante o processo de puxar. </li><li> Aquece-se a cilindro de alumina (que actua como um forno) por uma chama de oxigénio-butano-se a uma temperatura próxima de um ponto de fusão de sílica (cerca de 2100 ° C). </li><li> Inferir a adiabaticity do cone do OBSErvação da transmissão de um laser que opera a 635 nm. Verifique se na saída uma mancha circular homogênea é preservada, enquanto afinando, indicando que nenhum modo de embaralhamento ocorre. Pare de puxar e retirar a chama quando a potência transmitida oscilo batentes, e é constante ao longo do tempo. </li><li> Cole a fibra cónica para uma lâmina de microscópio de vidro em forma sob a forma de um U para acomodar o afilamento (ver figura 3b). Use uma lâmina de vidro de dimensões 76x26x1.2 mm. </li></ol> 3. Fabricação de Microesferas Pequenas Nota: As pequenas microsferas com diâmetros inferiores ao tamanho de uma fibra padrão folheado exige afilamento anterior da fibra. O diâmetro mínimo obtido usando este método é de cerca de 25 um. <ol><li> Seguindo a seção 2, desenhar uma fibra cônico, puxando até quebrar. </li><li> Siga todos os passos da secção 1 (fabricação de microesferas UHQ), mas na etapa 1.3, modifique os valores na co splicerntroller como se segue: o poder do arco 20, a duração de arco 1.200 ms. </li></ol> 4. acoplamento da luz para a microesfera Nota: Nós usamos o cone de luz casal no microesfera e medir as ressonâncias do microresonator. <ol><li> 4.1. Preparar um suporte / alumínio em forma de T de PVC com um canal no meio. Fixar a haste de fibra residual da microesfera com um pedaço de magia scotch ou fita adesiva de papel no suporte. Prenda o suporte com dois parafusos em uma fase de tradução com atuadores piezoelétricos e uma resolução de posicionamento de 20 nm. </li><li> Corrigir o cone colado à lâmina de vidro para outra fase de tradução com o plano de deslizamento posicionado perpendicularmente à haste de fibra de microesferas. Unir as extremidades do cone de cabos de fibra terminados. Conecte uma ponta a laser de diodo sintonizável e o outro a um detector de fotodiodo de InGaAs. </li><li> Use um tubo de microscópio com longa distância de trabalho (&gt; 20 mm) para control a lacuna entre o cone e microesfera. A fim de controlar o sistema em outro lugar direcção de um espelho a 45 ° em relação à direcção do tubo de modo que a posição do cone em relação ao equador da microesfera podem ser controlados. <ol><li> Posicionar o equador da microesfera em contacto com a fibra cónica. </li></ol></li><li> Ligue o laser e verificar o espectro de transmissão do sistema de microsferas atarraxamento num osciloscópio. <ol><li> Sintonize o laser CW operando a 1.550 nm até ressonâncias aparecer. As ressonâncias podem ser identificados como Lorentziana forma depressões no espectro. </li></ol></li><li> Medir a largura de linha de ressonância (full metade de largura máxima do mergulho em forma de Lorentz). Calcular o factor Q como a frequência da bomba dividida pela largura de linha de ressonância. </li><li> Reduzir / aumentar o fosso entre a esfera e o cone, alterando a largura de ressonância e profundidade para aumentar / diminuir a eficiência de acoplamento. </li></ol><pclass = &quot;jove_title&quot;&gt; 5. Stimulated Raman Scattering <ol><li> Inserir um érbio dopado amplificador de fibra (EDFA) entre o laser CW operando a 1.550 nm e o atenuador. O EDFA funciona na faixa de comprimento de onda de 1,530-1,570 nm. Nota: Isto irá aumentar a potência do laser, atingindo uma potência máxima de saída 2 efeitos não lineares W. precisa potências de entrada altas Figura 4 mostra um esboço da montagem experimental.. </li><li> Ligue uma extremidade do cone com cabos de fibra terminados para um divisor de 3 dBm. Conectar uma das fibras de saída do divisor para o analisador de espectro óptico e o outro para um fotodetector que está ligado ao osciloscópio. </li><li> Sintonize o laser de alta para baixas frequências até uma ressonância com uma deriva térmica comparável à velocidade de varredura de comprimento de onda do laser é encontrado. Quando o térmico de auto-travamento 20 é conseguido um alargamento da ressonância pode ser visto no osciloscópio. </li><li> Verifique a potência de saída transmitida através do conepara um analisador de espectro óptico. Aumentar o poder até que a linha de laser Raman aparece. É afinado, a partir do comprimento de onda da bomba a cerca de 13,5 THz. </li></ol>

<ol>
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The authors declare that they have no competing financial interests. D.F. is a PhD student at the University of Parma.

As microesferas são osciladores lineares compacta e eficiente e que são muito fáceis de fabricar e manusear. fibras afilado pode ser utilizado para o acoplamento e extrair a luz no / a partir do ressonador. Ressonância contraste de até 95% e factores Q de cerca de 3 x 10 8 pode ser obtido. A principal limitação destas técnicas de fabricação é a produção e integração de massa. Limpeza das fibras é crítica para ambas as microesferas e cones, e por isso é de humidad...

Sussurrando ressonadores Gallery Mode (WGMR) mostram duas propriedades únicas, uma vida inteira de fótons de comprimento e volume de modo pequeno que permitem a redução do limiar de fenômenos não lineares 1-3. Whispering modos galeria são modos ópticos que são confinadas na interface ar dieléctrico por reflexão total interna. O volume pequeno modo é devido à alta confinamento espacial enquanto que o confinamento temporal é relacionado com o factor de qualidade Q de cavidade. WGMR pode ter diferentes geometrias e há técnicas de fabricação diferentes adequados para a obtenção de ressonadores High Q 4-6 cavidades tensão de superfície, tais como microesferas de sílica exposição perto de rugosidade escala atômica, o que se traduz em fatores de alta qualidade. Ambos os tipos de confinamento reduzir significativamente o limiar para os efeitos não lineares, devido à forte acumulação de energia no interior do WGMR. Ele também permite contínuas onda (CW) não lineares óptica. WGMR pode ser descrito usando the números quânticos n, L, M e o seu estado de polarização, num forte analogia com o átomo de hidrogénio 7. A simetria esférica permite a separação em radial e dependências angulares. A solução radial é dada por funções de Bessel, os angulares pelos harmônicos esféricos 8. Vidro de sílica é centrossimétrico e, portanto, segundo fenômenos de ordem relacionadas com Χ (2) interações são proibidos. Na superfície da microesfera, a inversão de simetria é quebrada e Χ (2) os fenómenos pode ser observada uma. No entanto, as condições de casamento de fase para a geração de frequência de segunda ordem são mais problemáticas do que o equivalente em geração de terceira frequência ordem, especialmente porque os comprimentos de onda envolvidas são bastante diferentes e o papel de dispersão pode ser muito importante. O segundo interações de ordem são extremamente fracos. As escalas de energia gerados com Q 3 enquanto que para um thifim rd interação das escalas de energia gerados com Q 4. 9 Por essa razão, o foco deste trabalho é de terceira ordem óptica susceptibilidade não-linear Χ (3) interações tais como Stimulated Raman Scattering (SRS) e estimulou Antistokes Raman Scattering (SARS) , sendo SARS a interação menos exploradas 10,11. Chang 12 e Campillo 13 foi pioneiro nos estudos de fenômenos não lineares usando gotículas de materiais altamente não-lineares como WGMR mas o laser da bomba foi pulsado em vez de CW. Microesferas de sílica 14,10 e microtoroids 15 instaladas plataformas mais estáveis ​​e robustos em comparação com os micro-gotas, ganhando muita atenção nas últimas décadas. Particularmente, microesferas de sílica são muito fáceis de fabricar e manusear. SRS é um processo de ganho puro que pode ser facilmente alcançada em sílica WGMR 14,15, desde que atingiu um limiar é suficiente. Neste caso, o elevado circulating intensidade dentro do WGMR garante Raman de laser, mas para oscilações paramétricos não é suficiente. Nestes casos, as oscilações eficientes requerem fase e correspondência modo, a energia ea lei de conservação de impulso e uma boa sobreposição espacial de todos os modos de ressonância a ser cumprida 16-18. Este é o caso de SARS e FWM em geral.

<table><tbody><tr><td>Optical Fiber</td><td>Corning</td><td>SMF28</td><td></td></tr><tr><td>Fiber coating stripper</td><td>Thorlabs</td><td>T06S13</td><td>Available from other vendors as well</td></tr><tr><td>Fiber cleaver</td><td>Fitel</td><td>S325A</td><td>Available from other vendors as well</td></tr><tr><td>Fusion splicer</td><td>Furakawa</td><td>S177A-1R</td><td>Available from other vendors as well</td></tr><tr><td>Butane and Oxygen Gas</td><td>n/a</td><td></td><td>any vendor</td></tr><tr><td>Microscope tube</td><td>Navitar</td><td>Zoom 6000</td><td>Modular Kit</td></tr><tr><td>CCD camera</td><td>n/a</td><td>N/A</td><td>any will fit</td></tr><tr><td>Monitor</td><td>n/a</td><td>N/A</td><td>any monitor is valid</td></tr><tr><td>3-Axis Stage</td><td>PI Instruments, Thorlabs, Melles</td><td></td><td></td></tr><tr><td>Assorted posts and mounts</td><td>Thorlabs</td><td></td><td>Available from other vendors as well</td></tr><tr><td>Polarization control</td><td>Thorlabs</td><td>FPC030</td><td>Available from other vendors as well</td></tr><tr><td>Attenuator</td><td>Throlabs</td><td>VOA50</td><td></td></tr><tr><td>Photodiode</td><td>Thorlabs</td><td>PDA400</td><td>discontinued, replaced by PDA10CS-EC</td></tr><tr><td>Oscilloscope</td><td>Tektronix</td><td>DPO7104</td><td></td></tr><tr><td>Optical spectrum analyzer</td><td>Ando</td><td>AQ6317B</td><td></td></tr><tr><td>Erbium Doped Fiber Amplifier</td><td>IPG Photonics</td><td>EAD-2K-C</td><td></td></tr><tr><td>Tunable Laser</td><td>Yenista</td><td>TUNICS</td><td></td></tr></tbody></table>

stimulated stokes and antistokes raman scattering in microspherical whispering gallery mode resonators

microesferas dielétricos pode confinar luz e som para um período de tempo através do fator sussurrando modos galeria de alta qualidade (WGM). microesferas de vidro pode ser pensado como uma reserva de energia com uma enorme variedade de aplicações: fontes de laser compacta, sensores bioquímicos muito sensíveis e fenômenos não lineares. Um protocolo para o fabrico de ambos os micro-esferas e sistema de acoplamento é dada. Os acopladores aqui descritas são fibras afuniladas. Geração eficiente de fenômenos não lineares relacionadas com a terceira ordem susceptibilidade não-linear óptico Χ (3) interações em microesferas de sílica triplamente ressonantes é apresentada neste artigo. As interações aqui relatados são: Stimulated Raman Scattering (SRS), e quatro processos onda mistura compreendendo Stimulated Anti-Stokes Raman Scattering (SARS). Uma prova do fenómeno-cavidade reforçada é dada pela falta de correlação entre a bomba, sinal e complementar: um modo de ressonância tem de existir, a fim de obter o parde sinal e complementar. No caso de oscilações hyperparametric (mistura de quatro ondas e estimulou anti-Stokes espalhamento Raman), os modos deve cumprir a conservação de energia e impulso e, por último mas não menos importante, ter uma boa sobreposição espacial.

Os factores Q das microesferas fabricadas seguindo o protocolo descrito acima estão em excesso de 10 8 (Figura 5) para grandes diâmetros (&gt; 200 um) e um excesso de 10 6 para diâmetros pequenos (&lt;50 um). contraste de ressonância acima de 95% (perto de acoplamento crítico) pode ser facilmente observado. Para altas intensidades circulantes, podem ser observados os seguintes efeitos não lineares na região do infravermelho: estimulada espalh...

Watch this Scientific Journal Video about Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators at JoVE.com

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Estimulada Stokes e Antistokes Raman Scattering em microparticulas Whispering Gallery Modo Resonators

Geração eficiente de fenômenos não lineares relacionadas com a terceira ordem susceptibilidade não-linear óptico Χ (3) interações em microesferas de sílica triplamente ressonantes é apresentada neste artigo. As interações aqui relatados são: Stimulated Raman Scattering (SRS), e quatro processos onda mistura compreendendo Stimulated Anti-Stokes Raman Scattering (SARS).

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres ...

stimulated-stokes-antistokes-raman-scattering-microspherical

Research

JoVE Journal

Engineering

11.2K visualizações.  Enrico Fermi Center.  Geração eficiente de fenômenos não lineares relacionadas com a terceira ordem susceptibilidade não-linear óptico Χ (3) interações em microesferas de sílica triplamente ressonantes é apresentada neste artigo. As interações aqui relatados são: Stimulated Raman Scattering (SRS), e quatro processos onda mistura compreendendo Stimulated Anti-Stokes Raman Scattering (SARS). 

Vídeo: Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Rejection of Fluorescence Background in Resonance and Spontaneous Raman Microspectroscopy

Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ultrafast pulses, a system that can temporally separate spectrally overlapping signals on a picosecond timescale can isolate promptly arriving Raman scattered light from late-arriving fluorescence light. Here we discuss the construction and operation of a complex nonlinear optical system that uses all-optical switching in the form of a low-power optical Kerr gate to isolate Raman and fluorescence signals. A single 808 nm laser with 2.4 W of average power and 80 MHz repetition rate is split, with approximately 200 mW of 808 nm light being converted to &lt; 5 mW of 404 nm light sent to the sample to excite Raman scattering. The remaining unconverted 808 nm light is then sent to a nonlinear medium where it acts as the pump for the all-optical shutter. The shutter opens and closes in 800 fs with a peak efficiency of approximately 5%. Using this system we are able to successfully separate Raman and fluorescence signals at an 80 MHz repetition rate using pulse energies and average powers that remain biologically safe. Because the system has no spare capacity in terms of optical power, we detail several design and alignment considerations that aid in maximizing the throughput of the system. We also discuss our protocol for obtaining the spatial and temporal overlap of the signal and pump beams within the Kerr medium, as well as a detailed protocol for spectral acquisition. Finally, we report a few representative results of Raman spectra obtained in the presence of strong fluorescence using our time-gating system.

We discuss the construction and operation of a complex nonlinear optical
system that uses ultrafast all-optical switching to isolate Raman from fluorescence
signals. Using this system we are able to successfully separate Raman and fluorescence
signals utilizing pulse energies and average powers that remain biologically safe.

Rejeição de fundo de fluorescência em Ressonância e microspectroscopy Raman espontâneo

Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ...

Bioengenharia

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy1, micro-cavity laser technology2, optical communications3-6 as well as sensor technology. The WGM-based sensor applications include those in biology7, trace gas detection8, and impurity detection in liquids9. Mechanical sensors based on microsphere resonators have also been proposed, including those for force10,11, pressure12, acceleration13 and wall shear stress14. In the present, we demonstrate a WGM-based electric field sensor, which builds on our previous studies15,16. A candidate application of this sensor is in the detection of neuronal action potential.
The electric field sensor is based on polymeric multi-layered dielectric microspheres. The external electric field induces surface and body forces on the spheres (electrostriction effect) leading to elastic deformation. This change in the morphology of the spheres, leads to shifts in the WGM. The electric field-induced WGM shifts are interrogated by exciting the optical modes of the spheres by laser light. Light from a distributed feedback (DFB) laser (nominal wavelength of ~ 1.3 &mu;m) is side-coupled into the microspheres using a tapered section of a single mode optical fiber. The base material of the spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are used: (1) PDMS sphere with a 60:1 volumetric ratio of base-to-curing agent mixture, (2) multi layer sphere with 60:1 PDMS core, in order to increase the dielectric constant of the sphere, a middle layer of 60:1 PDMS that is mixed with varying amounts (2% to 10% by volume) of barium titanate and an outer layer of 60:1 PDMS and (3) solid silica sphere coated with a thin layer of uncured PDMS base. In each type of sensor, laser light from the tapered fiber is coupled into the outermost layer that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field.

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Desenvolvimento de Whispering Gallery Modo poliméricos Micro-ópticos sensores do campo eléctrico

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The ...

Engenharia

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The customized techniques developed in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators are presented. The protocols to obtain and characterize these resonators are detailed, and an explanation of some of their applications in microwave photonics is given.

Microwave Systems Fotônica Baseado Ressonadores-gallery de modo Whispering

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Fabricação e Teste de microfluídicos optomechanical osciladores

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample.

The paper describes a method for producing extreme nanowires by melt infiltration into carbon nanotubes and how 1D systems may be characterized and investigated using Resonance Raman Spectroscopy to determine vibrational and optical excitation energies.

Espectroscopia Raman de nanofios extremos e Outros Sistemas 1D

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the ...

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with &lt;10 MHz spectral-resolution and &lt;35 MHz Brillouin-shift measurement precision at &lt;100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.

Espectrômetro de espalhamento Brillouin estimulado assemelhace de alta velocidade para análise de Material

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

Fabricação de Microsferas de Polímeros para Resonadores Ópticos e Aplicações Laser

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Implementation of a Nonlinear Microscope Based on Stimulated Raman Scattering

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. SRS imaging modality can be obtained using commercial laser-scanning microscopes by equipping with a non-descanned forward detector with proper bandpass filters and lock-in amplifier (LIA) detection scheme. A schematic layout of a typical SRS microscope includes the following: two pulsed laser beams, (i.e., the pump and probe directed in a scanning microscope), which must be overlapped in both space and time at the image plane, then focused by a microscope objective into the sample through two scanning mirrors (SMs), which raster the focal spot across an x-y plane. After interaction with the sample, transmitted output pulses are collected by an upper objective and measured by a forward detection system inserted in an inverted microscope. Pump pulses are removed by a stack of optical filters, whereas the probe pulses that are the result of the SRS process occurring in the focal volume of the specimen are measured by a photodiode (PD). The readout of the PD is demodulated by the LIA to extract the modulation depth. A two-dimensional (2D) image is obtained by synchronizing the forward detection unit with the microscope scanning unit. In this paper, the implementation of an SRS microscope is described and successfully demonstrated, as well as the reporting of label-free images of polystyrene beads with diameters of 3 &#181;m. It is worth noting that SRS microscopes are not commercially available, so in order to take advantage of these characteristics, the homemade construction is the only option. Since SRS microscopy is becoming popular in many fields, it is believed that this careful description of the SRS microscope implementation can be very useful for the scientific community.

In this manuscript, the implementation of a stimulated Raman scattering (SRS) microscope, obtained by the integration of an SRS experimental set-up with a laser scanning microscope, is described. The SRS microscope is based on two femtosecond (fs) laser sources, a Ti-Sapphire (Ti:Sa) and synchronized optical parametric oscillator (OPO).

Implementação de um microscópio não-linear baseado em espalhamento Raman estimulado

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. ...

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional &#960;-conjugate Systems

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near infrared (near-IR) transitions, because it can overcome the low sensitivity of spontaneous Raman spectrometers in the near-IR region. Here, we describe technical details of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer that we have recently developed. A description of signal generation and optimization, measurement, data acquisition, and calibration and correction of recorded data is provided as well. We present an application of our spectrometer to analyze the excited-state dynamics of &#946;-carotene in toluene solution. A C=C stretch band of &#946;-carotene in the second lowest excited singlet (S2) state and the lowest excited singlet (S1) state is clearly observed in the recorded time-resolved stimulated Raman spectra. The femtosecond time-resolved near-IR stimulated Raman spectrometer is applicable to the structural dynamics of &#960;-conjugate systems from simple molecules to complex materials.

Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of &#946;-carotene in toluene is shown as a representative application.

Mediçãos de Raman estimuladas do tempo ultrarrápido de sistemas funcionais de πconjugados

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near ...

Química

Multiplex Chemical Imaging Based on Broadband Stimulated Raman Scattering Microscopy

Stimulated Raman scattering (SRS) microscopy is a nonlinear optical technique for label-free chemical imaging. This analytical tool delivers chemical maps at high speed, and high spatial resolution of thin samples by directly interrogating their molecular vibrations. In its standard implementation, SRS microscopy is narrowband and forms images with only a single vibrational frequency at a time. However, this approach not only hinders the chemical specificity of SRS but also neglects the wealth of information encoded within vibrational spectra. 
These limitations can be overcome by broadband SRS, an implementation capable of extracting a vibrational spectrum per pixel of the image in parallel. This delivers hyperspectral data that, when coupled with chemometric analysis, maximizes the amount of information retrieved from the specimen. Thus, broadband SRS improves the chemical specificity of the system, allowing the quantitative determination of the concentration of the different constituents of a sample. Here, we report a protocol for chemical imaging with broadband SRS microscopy, based on a home-built SRS microscope operating with a custom differential multichannel-lock-in amplifier detection. It discusses the sample preparation, alignment of the SRS apparatus, and chemometric analysis. By acquiring vibrational Raman spectra, the protocol illustrates how to identify different chemical species within a mixture, determining their relative concentrations.

We present a protocol to acquire chemical images with broadband stimulated Raman scattering (SRS) microscopy. Based on an SRS microscope that operates with differential multichannel-lock-in detection, the protocol describes the sample preparation, adjustment of the SRS apparatus, and chemometrics to disentangle different constituents of chemically heterogeneous samples.

Multiplex Imagem química baseada em banda larga estimulada raman dispersão microscopia

Stimulated Raman scattering (SRS) microscopy is a nonlinear optical technique for label-free chemical imaging. This analytical tool delivers chemical maps ...