Os autores gostariam de agradecer a Picometrix para fornecer o substrato LT-GaAs e agradecem o apoio financeiro de Michigan Espaço Grant Consortium, DARPA Prêmio Jovem Faculdade gerido pelo Dr. João Albrecht (contrato # N66001-10-1-4027), NSF CARREIRA Prêmio gerido pelo Dr. Samir El-Ghazaly (contrato # N00014-11-1-0096), ONR Young Investigator Award gerido pelo Dr. Paul Maki (contrato # N00014-12-1-0947), e ARO Young Investigator Award gerido pela Dr. Dev Palmer (contrato # W911NF-12-1-0253).

1. Plasmônica Fabrication Emitter Photoconductive <ol><li> Fabricar grades plasmônicos. <ol><li> Limpar a bolacha de semicondutor por imersão em acetona (2 minutos), seguido de isopropanol (2 min) e lavagem com água desionizada (10 seg.) </li><li> Seca-se a amostra com azoto e aquecer numa placa de aquecimento a 115 ° C durante 90 segundos para remover qualquer água remanescente. </li><li> Giro Microchem 950K PMMA A4 na amostra a 4.000 rpm por 45 seg. Pré-coze a resistir numa placa de aquecimento a 180 ° C durante 3 min. </li><li> Coloque a amostra em uma ferramenta de litografia por feixe de elétrons (JEOL JBX-6300-FS). Expor o padrão de grade plasmônica na dose base de cerca de 650 uC / cm 2, com uma tensão de aceleração de 100 kV. </li><li> Desenvolver PMMA por imersão da amostra num MIBC: IPA mistura de 1:3, durante 90 seg. Transferir imediatamente a amostra a uma soluo de isopropanol puro durante 60 segundos. </li><li> Lavar a amostra com a água desionizada durante 10 segundos e, em seguida, secar a amostra com azoto. </li><li> Coloque a amostra em uma stripper plasma (YES-CV200RFS). Descum a amostra com 30 W de potência de RF a 30 ° C com um sccm O 2 taxa de fluxo de 100 para 10 segundos. </li><li> Remover óxido de superfície por imersão numa HCl: H 2 0 03:10 mistura durante 30 seg. Transferir imediatamente a amostra a uma cascata de enxaguamento de água deionizada durante 4 min. </li><li> Transfira a amostra para um copo de água desionizada para minimizar a exposição ao oxigénio atmosférico antes de deposição de metal. </li><li> Aqui proveta contendo a amostra em água desionizada a um evaporador de metal (Denton SJ-20). Purgue a câmara e, em seguida, remover, secar, e carregar a amostra na câmara (estes passos deverá ser seguido sem interrupção para evitar a formação de óxido na superfície da amostra). </li><li> Bomba a câmara a uma pressão abaixo de 2x10 -6 Torr. Depósito de Ti / Au (50/450 A). </li><li> Ventilar a câmara e retire a amostra. </li><li> A fim de levantar-off do metal depositado, colocar a amostra em um suporte de Teflon em umacopo de acetona, cubra e deixe durante a noite. Descubra o copo, coloque-o em um agitador ultra-som, e espere até que todos os metais indesejados é removido (normalmente 30 segundos). </li></ol></li><li> Depósito SiO2 passivação. <ol><li> Limpe a amostra como nas etapas 1.1.1 - 1.1.2. </li><li> Coloque a amostra em uma ferramenta de deposição de plasma-enhanced de vapor químico (GSI PECVD). Depósito 1500 Å de SiO 2, a 200 ° C. </li></ol></li><li> Abrir vias de contato através de SiO 2. <ol><li> Limpe a amostra como nas etapas 1.1.1 - 1.1.2. </li><li> Girar em HMDS a 4.000 rpm por 30 seg. Girar em Megaposit SPR 220-3,0 photoresist a 4.000 rpm por 30 seg. Pré-coze a resistir numa placa de aquecimento a 115 ° C durante 90 seg. </li><li> Coloque a amostra ea placa de máscara em projeção de litografia de passo (GCA autostep 200). Alinhar a amostra e expor. </li><li> Pós-cozer o fotossensível exposta numa placa de aquecimento a 115 ° C durante 90 seg. </li><li> Desenvolver resistir no AZ 300 MIF desenvolvedor para 60 seg. </li><li> Imediatamente mover a amostra a uma cascata de enxaguamento de água deionizada durante 4 min. Seca-se a amostra com azoto. </li><li> Coloque a amostra em um etcher iônica reativa (LAM 9400). Etch SiO 2, utilizando um poder TCP RF de 500 W, a potência de RF Viés de 100 W, 15 sccm de SF6-, 50 sccm de C 4 F 8, 50 sccm de He, 50 sccm de Ar por 80 seg. </li><li> Remover a maior parte do material fotosensitivo colocando a amostra em acetona (5 min) seguido de isopropanol (2 min.) Enxágüe em água deionizada (10 seg.) Seque com nitrogênio. </li><li> Remover o material fotosensitivo residual através do carregamento da amostra num separador de plasma (SIM-CV200RFS). Retire o photoresist usando 800 W de potência de RF a 30 ° C com um sccm O 2 taxa de fluxo de 100 para 5 min. </li></ol></li><li> Fabricar antenas e linhas diagonais. <ol><li> Repita os passos 1.3.1 - 1.3.6 para antenas padrão e linhas diagonais. </li><li> Repita os passos 1.1.8 - 1.1.9 para remover o óxido de superfície. </li><li> Aqui o recipiente que contém a amostra ede água desionizada para um evaporador de metal (Denton SJ-20). </li><li> Ventilar a câmara e retire rapidamente, seque e coloque a amostra na câmara. </li><li> Bomba a câmara a uma pressão abaixo de 2x10 -6 Torr. Depósito de Ti / Au (10/4, 000 Â). </li><li> Ventilar a câmara e retire a amostra. </li><li> Repita o passo 1.1.13 para a decolagem do metal depositado. </li></ol></li><li> Pacote da amostra. <ol><li> Cole as bordas de uma lente de silicone mm de diâmetro, 12 hiper-hemisférica para uma máquina de lavar de alumínio de 2 polegadas, com 8 mm de orifício. </li><li> Cole uma placa PCB com traços de metal, para a qual pode-se facilmente de solda, para o lavador de alumínio. </li><li> Monte os plasmônicos fotocondutores terahertz protótipos emissor fabricados na lente de silicone usando epoxy fina. </li><li> Obrigacionistas fio as almofadas de contato do aparelho para uma placa de circuito impresso colado na mesma máquina de lavar alumínio. </li><li> Fios de solda para os traços de metal na placa PCB. </li><li> Ligação almofadas de contato do dispositivo para um analisador paramétrico (Hewlett pacoteard 4155A) usando fios soldadas aos blocos correspondentes da placa PCB para fins de teste. </li></ol></li></ol> 2. Plasmônica Caracterização Emitter Photoconductive <ol><li> Alinhamento dispositivo. <ol><li> Coloque a arruela de alumínio levando os plasmônicos fotocondutores terahertz protótipos emissor em uma montagem de rotação e força se concentrar na bomba a partir de uma ótica Ti: Sapphire mode-locked (MIRA 900D V10 XW OPT 110V) para a área ativa de cada dispositivo. </li><li> Regular a montagem de rotação de tal forma que o campo eléctrico da bomba óptico é orientada para a excitação eficiente de ondas de plasma de superfície (perpendicular às grades plasmônicos). </li><li> Usar o analisador paramétrico para simultaneamente aplicar tensões de polarização a cada dispositivo e medir a corrente eléctrica induzida em cada dispositivo. Confirme o alinhamento da bomba óptico ideal e ajuste de polarização, maximizando a fotocorrente de cada dispositivo em teste. </li></ol></li><li> Medição de potência de saídaurement. <ol><li> Usar um triturador óptica (Thorlabs MC2000) para modular a bomba óptica do mode-locked de laser incidente bomba em cada dispositivo. </li><li> Medir a potência dos fotocondutores protótipos emissor terahertz plasmônicos usando um detector pyroelectric (Spectrum Detector, Inc. SPI-A-65 THz) de saída. </li><li> Ligue a saída do detector pyroelectric a um amplificador lock-in (Stanford Research Systems SR830), com frequência de referência do helicóptero óptico para recuperar os dados de potência terahertz em baixos níveis de ruído. </li></ol></li><li> Caracterização espectral de radiação. <ol><li> Comece com um Ti: Safira laser de modo-bloqueado e utilizar um divisor de feixe para dividir a saída do laser de modo bloqueado num feixe de bomba e um feixe de sonda. </li><li> Utilização de um modulador electro-óptico (EO Thorlabs-AM-NR-C2) para modular o feixe óptico no caminho da bomba. Focar o feixe de bomba para a área ativa do emissor photoconductive em teste para gerar radiação terahertz. </li><li> Colimaro feixe terahertz gerada usando uma primeira lente esférica de polietileno. Focar o feixe colimado terahertz usando uma segunda lente esférica de polietileno. </li><li> Antes da focagem do feixe de terahertz, combinar o feixe colimado terahertz com o feixe óptico de sonda, utilizando um filtro de vidro revestido de ITO. </li><li> Coloque a 1 mm de espessura, &lt;110&gt; ZnTe cristal montado numa fase de rotação no foco do feixe combinado de óptica e terahertz. </li><li> Insira uma linha de atraso óptico controlável no caminho óptico da sonda usando uma fase linear motorizado (Thorlabs NRT100) para variar o tempo de atraso entre os impulsos ópticos e terahertz interagem no interior do cristal ZnTe. </li><li> Usando uma meia-waveplate no caminho da sonda, rodar a polarização do sensor óptico para estar a um ângulo de 45 ° em relação à direcção de polarização terahertz. </li><li> Use um quarto de waveplate após o cristal ZnTe, converter a polarização do feixe óptico em polarização circular. </li><li> Divida o circulfeixe óptico Arly polarizada em dois ramos por um prisma Wollaston. Medir a potência do feixe óptico em cada ramo com dois detectores equilibradas ligados a um amplificador lock-in. </li><li> Ligação da linha de atraso e motorizado amplificador lock-in para um computador. Escreva um script Matlab para iteratively mover a posição da linha de atraso motorizado, pausar e ler a magnitude do sinal do amplificador lock-in. </li><li> Converter a posição de fase para o domínio do tempo, por meio de divisão do comprimento de atraso total óptica pela velocidade da luz, seguindo-se uma transformada de Fourier discreta (Matlab) para obter os dados de domínio de frequência. </li></ol></li></ol>

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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+thermal+conductivity+in+low-temperature+grown+GaAs.">Reduced thermal conductivity in low-temperature grown GaAs.</a> Appl. Phys. Lett. 74, 2325-2327 (1999).</li></ol>

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Neste artigo de vídeo, apresentamos uma nova técnica de geração de terahertz fotocondutivo que utiliza uma configuração de eléctrodo de contacto plasmônica para aumentar a eficiência da conversão óptica para terahertz por duas ordens de magnitude. O aumento significativo no poder de radiação terahertz dos apresentados emissores fotocondutores plasmônicos é muito importante para o futuro de alta sensibilidade terahertz imaging, espectroscopia e espectrometria de sistemas usados ​​para identificação q...

Apresenta-se um novo emissor de terahertz fotocondutivo que utiliza uma configuração de eléctrodo de contacto plasmônica para aumentar a eficiência da conversão óptica para terahertz por duas ordens de magnitude. Nossa técnica aborda as limitações mais importantes emissores convencionais fotocondutores terahertz, ou seja, de baixa potência de saída e baixa eficiência de energia, que se originam a partir da compensação inerente entre a alta eficiência quântica e operação ultra-rápida de fotocondutores convencionais. Uma das novidades chave na nossa concepção, que conduziram a esta melhoria de desempenho é saltar para desenhar uma configuração de eléctrodo de contacto que se acumula de um grande número de portadores foto-gerados em estreita proximidade com os eléctrodos de contacto, de tal modo que elas podem ser recolhidas através de um sub- picosecond prazo. Em outras palavras, o equilíbrio entre a operação de ultra fotocondutor e alta eficiência quântica é atenuado pela manipulação espacial do foto-génerosportadores TED. Eletrodos de contato plasmônicos oferecer esta capacidade única de (1) permitir o confinamento da luz em dispositivos em nanoescala áreas ativas entre os eletrodos plasmônicos (além do limite de difração), (2) melhoria luz extraordinária no contato de metal e fotos de absorção de semicondutores interface de 10, 11. Outra característica importante da nossa solução é que acomoda grandes áreas activas fotocondutoras, sem um considerável aumento na carga parasitária da antena irradia terahertz. Utilizando grandes áreas activas fotocondutoras permitir mitigar o efeito de blindagem transportador e degradação térmica, que são as limitações de final para a potência máxima de radiação de emissores fotocondutoras convencionais. Este artigo de vídeo está concentrada nos atributos únicos da nossa solução apresentada por descrever a física que regem, modelagem numérica e verificação experimental. Nós demonstramos experimentalmente 50 vezes maiores poderes terahertz de um phot plasmônicaemissor oconductive em comparação com um emissor de fotocondutor semelhante com eléctrodos de contacto não plasmônicos.

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design, fabrication, and experimental characterization of plasmonic photoconductive terahertz emitters

Neste artigo de vídeo, apresentamos uma demonstração detalhada de um método altamente eficiente para a geração de ondas terahertz. A técnica baseia-se fotocondução, que tem sido uma das técnicas mais utilizadas para geração de terahertz 1-8. Geração Terahertz num emissor fotocondutiva é conseguida bombeando uma ultra fotocondutora com uma iluminação laser pulsado ou heterodyned. A fotocorrente induzida, que segue o invólucro do laser de bomba, é encaminhado para uma antena irradia terahertz ligado aos eléctrodos de contacto fotocondutoras para gerar radiação terahertz. Embora a eficiência quântica de um emissor photoconductive teoricamente pode chegar a 100%, os de transporte relativamente longos comprimentos de trajeto de portadores foto-gerados para os eletrodos de contato de fotocondutores convencionais severamente limitada a sua eficiência quântica. Além disso, o efeito de triagem de portadores e degradação térmica limitar estritamente a produção máxima power de fontes de terahertz fotocondutores convencionais. Para resolver as limitações de eficiência quântica de emissores terahertz fotocondutoras convencionais, temos desenvolvido um novo conceito emissor fotocondutivo que incorpora uma configuração de eléctrodo de contacto plasmônicos para oferecer maior eficiência quântica e operação ultra simultaneamente. Usando eletrodos de contato plasmônicos nano-escala, reduzir significativamente a foto gerada caminho transporte transportadora média para eletrodos de contato fotocondutores comparação com fotocondutores convencionais 9. O método também permite aumentar a área activa fotocondutor sem um considerável aumento na carga capacitiva da antena, aumentando a potência máxima radiação terahertz, evitando o efeito de triagem de portadores e degradação térmica a altas potências ópticas de bomba. Ao incorporar eletrodos de contato plasmônicos, demonstramos aumentar a eficiência de conversão de energia óptica-to-terahertz de um photoconductive te convencionalrahertz emissor por um factor de 50 10.

Para demonstrar o potencial de eletrodos plasmônicos para aumento de potência terahertz, que fabricou dois emissores terahertz: a convencional (Figura 1a) e plasmônica (Figura 1b) emissor photoconductive incorporando eletrodos de contato plasmônicos para reduzir os tempos de transporte transportadora entrar em contato com os eletrodos. Ambos os modelos de consistir num fotocondutor ultra com 20 mM lacuna entre ânodo e cátodo contactos, ligado a uma antena de gravata-borboleta long...

Watch this Scientific Journal Video about Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters at JoVE.com

Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

Nós descrevemos métodos para o design, fabricação e caracterização experimental de emissores fotocondutores plasmônicos, que oferecem duas ordens de níveis mais elevados de energia terahertz magnitude em comparação com emissores fotocondutores convencionais.

Projeto, fabricação e Experimental Caracterização de plasmônicos Emissores Terahertz Photoconductive

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on ...

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14.8K visualizações.  University of Michigan. Nós descrevemos métodos para o design, fabricação e caracterização experimental de emissores fotocondutores plasmônicos, que oferecem duas ordens de níveis mais elevados de energia terahertz magnitude em comparação com emissores fotocondutores convencionais.

Vídeo: Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators 1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.
Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides 3, asymmetric split-ring resonators 4, and photonic band gap structures integrated into parallel-plate waveguides 5. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.
The sensor design we use here is based on a simple parallel-plate waveguide 6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove 6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index 9.
Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves 10. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.

The procedure for implementing a refractive index sensor for terahertz frequencies based on a grooved parallel-plate waveguide geometry is described here. The method yields a measurement of the refractive index of a small volume of liquid through monitoring of the shift in the resonant frequency of the waveguide structure

Sensoriamento terahertz microfluídicos usando um sensor de guia de onda de placas paralelas

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic ...

Engenharia

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

Fabricação de simulação, e Caracterização de THz Absorvedores de metamateriais

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11
Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption.
To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues.
The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and power, as we can characterise a bare photonic crystal with access waveguides, without need for on-chip interference components, and the setup only consists of a Mach-Zehnder interferometer, with no need for moving parts and delay scans.
When characterising photonic crystal cavities, techniques involving internal sources21 or external waveguides directly coupled to the cavity27 impact on the performance of the cavity itself, thereby distorting the measurement. Here, we describe a novel and non-intrusive technique that makes use of a cross-polarised probe beam and is known as resonant scattering (RS), where the probe is coupled out-of plane into the cavity through an objective. The technique was first demonstrated by McCutcheon et al.28 and further developed by Galli et al.29

Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).

Fabricação e caracterização de guias de onda de luz de cristal fotônico lentas e cavidades

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view ...

Fabrication and Characterization of Disordered Polymer Optical Fibers for Transverse Anderson Localization of Light

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed polymer optical fiber is composed of 80,000 strands of poly (methyl methacrylate) (PMMA) and polystyrene (PS) that are randomly mixed and drawn into a square cross section optical fiber with a side width of 250 &mu;m. Initially, each strand is 200 &mu;m in diameter and 8-inches long. During the mixing process of the original fiber strands, the fibers cross over each other; however, a large draw ratio guarantees that the refractive index profile is invariant along the length of the fiber for several tens of centimeters. The large refractive index difference of 0.1 between the disordered sites results in a small localized beam radius that is comparable to the beam radius of conventional optical fibers. The input light is launched from a standard single mode optical fiber using the butt-coupling method and the near-field output beam from the disordered fiber is imaged using a 40X objective and a CCD camera. The output beam diameter agrees well with the expected results from the numerical simulations. The disordered optical fiber presented in this work is the first device-level implementation of 2D Anderson localization, and can potentially be used for image transport and short-haul optical communication systems.

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. This microstructured fiber can transport a small localized beam with a radius that is comparable to the beam radius of conventional optical fibers.

Fabricação e caracterização de polímeros desordenados fibras ópticas para Transverse Anderson localização da Luz

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

Patterning via ópticos de saturação Transitions - Fabricação e caracterização

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

Impressão Fabricação de massa Heterojunction células solares e<em&gt; In Situ</em&gt; Morfologia Caracterização

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Free-form Light Actuators &amp;#8212; Fabrication and Control of Actuation in Microscopic Scale

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

Atuadores de luz de forma livre - Fabricação e Controle de atuação em escala microscópica

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Fabricação e caracterização de supercondutores Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR is not affected by environmental characteristics such as the temperature and pressure surrounding the resonator. Electromagnetic radiation in THz frequencies is biocompatible, which is a critical condition especially for the application of the biomolecular sensing. However, the quality factor (Q-factor) and frequency responses of traditional thin-film based split ring resonator (SRR) MMs are very low, which limits their sensitivities and selectivity as sensors. In this work, novel nanopillar-based SRR MMs, utilizing displacement current, are designed to enhance the Q-factor up to 450, which is around 45 times higher than that of traditional thin-film-based MMs. In addition to the enhanced Q-factor, the nanopillar-based MMs induce a larger frequency shifts (17 times compared to the shift obtained by the traditional thin-film based MMs). Because of the significantly enhanced Q-factors and frequency shifts as well as the property of biocompatible radiation, the THz nanopillar-based SRR are ideal MMs for the development of biomolecular sensors with high sensitivity and selectivity without inducing damage or distortion to biomaterials. A novel fabrication process has been demonstrated to build the nanopillar-based SRRs for displacement current mediated THz MMs. A two-step gold (Au) electroplating process and an atomic layer deposition (ALD) process are used to create sub-10 nm scale gaps between Au nanopillars. Since the ALD process is a conformal coating process, a uniform aluminum oxide (Al2O3) layer with nanometer-scale thickness can be achieved. By sequentially electroplating another Au thin film to fill the spaces between Al2O3 and Au, a close-packed Au-Al2O3-Au structure with nano-scale Al2O3 gaps can be fabricated. The size of the nano-gaps can be well defined by precisely controlling the deposition cycles of the ALD process, which has an accuracy of 0.1 nm.

A protocol for the design and fabrication of a novel nanopillar-based split ring resonator (SRR) is presented.

Fabricação de ressonadores anel de divisão Nanopillar-base para o deslocamento atuais mediada Ressonâncias em Terahertz Metamaterials

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR ...

Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

Here, we demonstrate the advantages of the laser Doppler vibrometer (LDV) over conventional techniques (the network analyzer), as well as the techniques to create an application-based microelectromechanical systems (MEMS) filter and how to use it efficiently (i.e., tuning the tuning-capability and avoiding both failure and stiction). LDV enables crucial measurements that are impossible with the network analyzer, such as higher mode detection (highly sensitive biosensor application) and resonance measurement for very small devices (fast prototyping). Accordingly, LDV was used to characterize the frequency tuning range and resonance frequency at different modes of the MEMS filters built for this study. This wide range frequency tuning mechanism is based simply on Joule heating from the embedded heaters and relatively high thermal stress with respect to the temperature of a fixed-fixed beam. However, we demonstrate that another limitation of this method is the resulting high thermal stress, which can burn the devices. Further improvement was achieved and shown for the first time in this study, such that the tuning capability was increased by 32% through an increase in the applied DC bias voltage (25 V to 35 V) between the two adjacent beams. This important finding eliminates the need for the extra Joule heating at the wider frequency tuning range. Another possible failure is through stiction and requirement of structure optimization: We propose a simple and easy technique of low frequency square wave signal application that can successfully separate the beams and eliminates the need for the more sophisticated and complicated methods given in the literature. The above findings necessitate a design methodology, and so we also provide an application-based design.

A protocol for a fixed-fixed beam design using a laser Doppler vibrometer (LDV), including the measurement of frequency tuning, modification of tuning capability, and avoidance of device failure and stiction, is presented. The superiority of the LDV method over the network analyzer is demonstrated due to its higher mode capability.

Projeto e metodologia de caracterização para filtros de MEMS sintonizável eficiente gama

Here, we demonstrate the advantages of the laser Doppler vibrometer (LDV) over conventional techniques (the network analyzer), as well as the techniques ...