Este material é baseado no trabalho apoiado por um fundo de arranque, na Universidade de Minnesota, Twin Cities. Partes deste trabalho foram realizadas na instalação de caracterização da Universidade de Minnesota, um membro da Materials Research Facilities Rede NSF-financiado (www.mrfn.org) através do programa MRSEC. Uma porção deste trabalho também foi realizado na Minnesota Nano Center, que recebe o apoio parcial do NSF através do programa NNCI.

Cuidado: Muitos dos produtos químicos utilizados nestas sínteses são tóxicos, altamente inflamável e pode causar irritação e danos em órgãos grave quando tocado ou inalado. Por favor, usar equipamento de proteção pessoal adequado (PPE) ao manusear. 1. Preparação de a primeira camada de ouro (Au) Nanopillar matrizes (Figura 2A-C e Figura 2e-g) <ol><li> Preparação de cobre (Cu) camadas de sementes para Au galvanoplastia (Figura 2a, b e Figura 2E, F) <ol><li> Usar uma bolacha 4 &quot;alta resistividade de silício (Si). (Resistividade: 560-840 Ω · cm) como o substrato A bolacha de Si do tipo N é dopado e polido de um lado (Figura 2A, e). </li><li> Cortar a bolacha de Si 2 cm x 2,5 cm peças para uso posterior. </li><li> Depositar uma camada de 5 nm de crómio (Cr) sobre a amostra de Si utilizando um processo de evaporação de feixe de electrões (E-beam) como uma camada de adesão entre o Si e Cu. </li><li> Depositar uma camada de 10 nm de Cu no topo da camada de Cr existente usando umProcesso de evaporação de feixe de electrões como a camada de semente para Au galvanoplastia (Figura 2b, F). </li></ol></li><li> Galvanoplastia a matriz nanopillar Au (Figura 2c, g) <ol><li> Padronização da matriz nanopillar <ol><li> Girar revestimento fotorresiste sobre a amostra preparada no ponto 1.1 a 2.000 rpm durante 60 s. </li><li> Cozer a amostra numa placa quente a 115 ° C durante 60 s. </li><li> Expor o fotorresistente sob luz ultravioleta (UV) -Light (poder de ~ 15 mW / cm 2) com uma fotomáscara Cr que contém milhares de padrões nanopillar durante 22 s. </li><li> Desenvolver com um desenvolvedor por 90 s com agitação. </li><li> Lavar a amostra com deionizada (DI) de água e seque a amostra com uma pistola de ar. </li></ol></li><li> Galvanoplastia a matriz nanopillar Au <ol><li> Retirar a parte superior do foto-resistente sobre a amostra com acetona para expor a camada de semente de Cu para ligação do eléctrodo. </li><li> Ligue o sample (camada de sementes Cu) ao terminal negativo de um metro de origem usando uma pinça e um fio. Neste caso, a amostra é o ânodo durante o processo de galvanização. </li><li> Conectar um pedaço de platina (Pt) Si (mesmo tamanho da amostra) revestido com o terminal positivo da fonte de metros. O PT é o cátodo, durante o processo de galvanização. </li><li> Submerge tanto o cátodo de Pt e Cu ânodo na solução de galvanoplastia Au. Manter os dois eléctrodos de frente um para o outro com uma distância de ~ 1 cm. </li><li> Ligue o medidor de origem e fornecer uma tensão constante de 1,12 V. Electroplate Au na amostra para 8 min (taxa de deposição: ~ 100 nm / min). </li><li> Lavar a amostra com água desionizada, seguido por acetona para remover o material fotosensitivo. </li><li> Lavar a amostra com água DI novamente e seque com uma pistola de ar. </li><li> Inspecione a matriz galvanizado nanopillar Au sob um microscópio. </li><li> Medir a espessura da UA nanopillars com um perfilómetro (A espessura doAu nanopillars é de ~ 800 nm). NOTA: Constante atual set-up também pode ser usado para galvanizar Au nanopillars. Em ambos tensão constante e aparelhagem de corrente constante, a tensão de corrente ideal e usado para Au galvanização pode ser conseguida por tentativa e erro. </li></ol></li></ol></li></ol> 2. Criação de Nano-lacunas entre Au Nanopillars (Figura 2d, h) <ol><li> A remoção de camadas de Cr e Cu <ol><li> Submergir a amostra em Cu etchant até a cor Cu desaparece. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li><li> Inspecione os nanopillars Au sob um microscópio. </li><li> Submergir a amostra em Cr máscara etchant por 10 s. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li><li> Inspecione os nanopillars Au sob um microscópio. </li></ol></li><li> Fabricação de nano-escala óxido de alumínio (Al 2 O 3) lacunas <ol><li> Aqueça o cham sistema ALDber a 200 ° C. </li><li> Colocar a amostra no centro da câmara. </li><li> Pump down a câmara a um vácuo e definir o número de ciclos a 100 (taxa de deposição: ~ 1 A / ciclo). </li><li> Sequencialmente e, alternativamente, o pulso de gás trimetilalumínio (TMA), com um período de tempo de 0,015 s e (H2O) de vapor de água com um período de tempo de 0,015 s para dentro da câmara de depósito uniforme de Al 2 O 3 camadas sobre a amostra. O intervalo de tempo entre cada pulso é de 5 s. A pressão da câmara durante o impulso TMA é de 10 Torr e a pressão durante 2 pulso O vapor H é de 2 Torr. </li><li> Purgar e aspirar a câmara entre cada ciclo da deposição. Depósito Al 2 O 3 de 100 ciclos e tirar a amostra da câmara. </li><li> Medir a espessura do ALD Al 2 O 3, utilizando um elipsómetro. </li></ol></li></ol> 3. Preparação da segunda camada de uma película fina Au (Figura 2i-l e A Figura 2 M-P) <ol><li> Preparação de camadas de sementes de Cu para Au galvanoplastia (Figura 2-I, m) <ol><li> Colocar a amostra no centro de um suporte de amostras evaporador E-feixe. </li><li> Desligar a rotação da amostra no evaporador de feixe de electrões. </li><li> Depositar uma camada de Cr de 5 nm na amostra para actuar como uma camada de adesão entre Al 2 O 3 e Cu. Use um processo de evaporação E-feixe, sem rotação da amostra. </li><li> Depósito de 10 nm de Cu no topo da camada de Cr existente usando um processo de evaporação de feixe de electrões sem rotação da amostra como a camada de semente para Au galvanoplastia. </li></ol></li><li> Galvanoplastia a película fina Au (Figura 2j, n) <ol><li> Ligar a amostra (camada de sementes Cu) ao terminal negativo da fonte de metros usando uma pinça e um fio. Neste caso, a amostra é o ânodo durante o processo de galvanização. </li><li> Ligue o cátodo de Pt ao terminal positivo da fonte de metros. </li><li> Submerge tanto o cátodo de Pt e Cu anode na solução de galvanoplastia Au. Manter os dois eléctrodos de frente um para o outro com uma distância de ~ 1 cm. </li><li> Ligue o medidor de fonte e criar tensão constante de 1,35 V e galvaniza Au com a amostra para 16 min. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li><li> Inspecione o Au galvanizado ea matriz previamente galvanizado nanopillar Au sob um microscópio. </li><li> Medir a espessura da UA nanopillars com um perfilômetro (Espessura da UA nanopillars é de ~ 400 nm). NOTA: Semelhante ao galvanoplastia Au no ponto 1.2.2, corrente constante set-up também pode ser usado para galvanizar Au película fina. Em ambos tensão constante e aparelhagem de corrente constante, a tensão de corrente ideal e usado para Au galvanização pode ser conseguida por tentativa e erro. </li></ol></li><li> Remoção de Cr e Cu camadas (Figura 2k, o) <ol><li> Submergir a amostra em Cu etchant por 10 s. </li><li> Lavar a amostra com DI de águad blow-seca, com uma pistola de ar. </li><li> Inspecione os nanopillars Au sob um microscópio. </li><li> Submergir a amostra em Cr máscara etchant por 10 s. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li><li> Inspecione os nanopillars Au sob um microscópio. NOTA: Como alternativa, submergir a amostra na solução de galvanoplastia Au novamente para depositar uma camada extra de Au no topo da segunda camada de Au electrodepositado após a remoção de Cr e Cu (passo 3.3). Esta camada extra Au aumenta a espessura total da segunda camada de Au e garante um bom contacto entre a camada de Au e a camada de Al 2 O 3 (Figura 2i, p). </li></ol></li></ol> 4. Definição do C-forma SRR (Figura 2T-s e Figura 2U-w) <ol><li> Padronização do SRR C-forma (Figura 2T, u) <ol><li> Girar um revestimento foto-resistente sobre a amostra a 2000 rpm durante 60 s. </li><li> Asse a amostra na placa quente de 115 ° C durante 60 s. </li><li&gt; Expor fotorresistente sob luz UV (fonte de ~ 15 mW / cm 2) com uma fotomáscara Cr durante 22 s. </li><li> Desenvolver com um desenvolvedor por 90 s com agitação. </li><li> Lavar a amostra com água DI e seque a amostra com uma pistola de ar. </li></ol></li><li> Definição em forma de C usando moinhos de iões (Figura 2R, V e Figura 2s, w) <ol><li> Fixe a amostra num suporte de amostras moinho de iões utilizando fita condutora dupla face Cu. </li><li> Esfriar a câmara de moagem ion a 6 ° C. </li><li> Ion moinho a amostra com um feixe de tensão de 300 V e uma corrente de feixe de 125 mA durante ~ 30 min. </li><li> Retire a amostra e inspecionar os nanopillars Au fora da C-forma. </li><li> Repita o passo 4.2.3 e 4.2.4, se Au ainda é visível fora do C-forma. </li><li> Sonicar a amostra em acetona, para remover o material fotosensitivo. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li><li> Inspeccionar a amostra sob um microscópio. </li><li> Repita o passo 4.2.6 e 4.2.7 Se fotorresistência não é totalmente removido. NOTA: Como alternativa, aplique oxigênio resistem amolecimento passos para o fotorresiste antes de remover o fotorresiste. No entanto, num banho de ultra-sons é o método mais eficaz para remover o material fotosensitivo, se aplicável. </li></ol></li></ol> 5. Remoção de Al 2 O 3 para a Air Nano-lacunas (Figura 2t, x) <ol><li> Submergir a amostra em solução a 5% de fluoreto de hidrogénio (HF) durante 5 min para remover Al 2 O 3. </li><li> Lavar a amostra com água DI e secar com uma pistola de ar. </li></ol>

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Esta técnica de fabricação tem vantagens significativas para a criação de estruturas em escala nanométrica em relação aos métodos existentes, tais como a litografia de feixe de electrões e auto-montagem. Em primeiro lugar, as estruturas em escala nano pode ser realizado por uma grande área (uma bolacha inteira) usando um photomask que apresenta matrizes nanopillar, que não é prático com um processo de litografia de feixe de electrões. Em segundo lugar, o processo de fabrico utiliza um processo de fabrica?...

Terahertz (THz) metamateriais (MMS) foram desenvolvidos para sensores biomédicos e dispositivos de 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 freqüência ágil. A fim de melhorar a sensibilidade e a frequência selectividade dos sensores MM THz, um baseado em nanopillar anel fendido ressonador (SRR) foi concebido usando corrente de deslocamento gerado dentro de ouro (Au) matrizes nanopillar para excitar ressonâncias THz com factores de ultra-alta qualidade ( Q-fatores) (~ 450) (Figura 1) 12. Mesmo que SRR baseada nanopillar mostram altos Q-fatores e habilidades de detecção promissores, fabricação de tais nanostructures com proporções elevadas (mais de 40) e lacunas escala nano (sub-10 nm) sobre uma grande área continua sendo um desafio 13. A técnica mais comumente usado para o fabrico de estruturas em escala nanométrica é por feixe de elétrons de litografia (EBL) 14, 15, 16, 17. No entanto, a resolução de EBL é ainda limitada, devido ao tamanho do ponto do feixe, de dispersão de electrões, as propriedades da resistência, e o processo de desenvolvimento 18, 19. Além disso, não é prático para fabricar nanoestruturas usando EBL sobre uma grande área devido a um tempo de processo lento e grandes custos de processo 20. Outra estratégia para alcançar nanoestruturas é a utilização de uma técnica de auto-montagem 21, 22. Por nanocubes metálicos auto-montagem (NCS) em uma solução e utilnalizar a interação eletrostática e a associação de ligantes de polímero entre CNs, uma matriz NC unidimensional bem organizado, com lacunas escala nano pode ser alcançado 23. O tamanho nano-lacuna depende dos ligandos de polímero entre as CNs e pode ser controlado através da aplicação de diferentes materiais de polímeros com diferentes pesos moleculares 24, 25, 26. Auto-montagem é uma técnica poderosa para alcançar nanoestruturas escaláveis e de custo eficiente 23. No entanto, o processo de fabricação é mais complicado comparado com os processos micro e nano fabricação convencionais, eo controle de tamanhos nano-gap não é suficientemente precisa para aplicações de dispositivos eletrônicos. A fim de fabricar com sucesso SRR baseada nanopillar, um novo método de fabrico, deverão ser inventada para atingir os seguintes objectivos: i) o processo de fabricação é fácil de aplicar e é compatível com a convençãoao micro e nano fabricação processos; ii) a fabricação de uma grande área é aplicável; iii) tamanhos nano-lacuna pode ser fácil e precisamente controlada com uma resolução de 0,1 nm e pode ser reduzida para 10 nm ou menos. Um novo método de fabricação é demonstrada usando a combinação de um processo de galvanoplastia e um processo de deposição de camada atómica (ALD) para fabricar SRR-base nanopillar. Desde galvanoplastia é um processo de auto-enchimento com baixo custo, que é fácil de fabricar estruturas sobre uma grande área. ALD é um processo de deposição de vapor químico (CVD) que pode ser precisamente controlada pelo ciclo de reacção durante o processo. A resolução de película fina ALD pode ser de 0.1 nm, e a película fina é uniformemente revestida com uma elevada qualidade, que é adequado para criar lacunas escala nano 27, 28. SRR matriz à base de Nanopillar com lacunas 10 nm ou menos pode ser fabricada com sucesso através de uma área de 6 mm x 6 mm. ambos sespectros de transmissão THz imulated e medidos mostram comportamentos ressonantes com ultra-alta Q-fatores e mudanças de frequência grandes, o que prova a viabilidade dos SRR baseada nanopillar mediadas pela corrente de deslocamento. O processo de fabricação detalhada está descrita abaixo na seção de protocolo eo protocolo de vídeo pode ajudar os profissionais a compreender o processo de fabricação e evitar erros comuns associados com a fabricação de SRR baseada nanopillar.

<table><tbody><tr><td>Silicon Wafer</td><td>Siltronic AG</td><td>N/A</td><td>100 mm diameter, N-type, one-side polish, resitivity: 560-840 &amp;Omega;&amp;bull;cm</td></tr><tr><td>Chromium</td><td>Kurt J. Lesker Company</td><td>EVMCR35J</td><td>99.95% pure</td></tr><tr><td>Copper</td><td>Kurt J. Lesker Company</td><td>EVMCU40QXQJ</td><td>99.99% pure</td></tr><tr><td>E-Beam Evaporator System</td><td>Rocky Mountain Vacuum Tech.</td><td>N/A</td><td>RME-2000</td></tr><tr><td>S1813 Positive Photoresist</td><td>Microposit</td><td>10018348</td><td>N/A</td></tr><tr><td>Spinner</td><td>Best Tools</td><td>S0114031123</td><td>SMART COATER 100</td></tr><tr><td>Mask Aligner</td><td>Midas</td><td>MDA-400LJ</td><td>N/A</td></tr><tr><td>Digital Hot Plate</td><td>Thermo Scientific</td><td>HP131725</td><td>Super-Nuvoa series, maximum temperature: 370 &amp;deg;C</td></tr><tr><td>MF319 Developer</td><td>Microposit</td><td>10018042</td><td>N/A</td></tr><tr><td>Acetone</td><td>Fisher Chemical</td><td>A18P-4</td><td>N/A</td></tr><tr><td>Isopropyl Alcohol</td><td>Fisher Chemical</td><td>A416-4</td><td>N/A</td></tr><tr><td>Gold 25 ES RTU</td><td>Technic Inc.</td><td>391427</td><td>N/A</td></tr><tr><td>Source Meter</td><td>Keithley</td><td>N/A</td><td>2612 System SourceMeter</td></tr><tr><td>Microscope</td><td>Omax</td><td>NJF-120A</td><td>N/A</td></tr><tr><td>Profilometer</td><td>Tencor Instruments</td><td>N/A</td><td>Alpha-Step 200</td></tr><tr><td>APS Copper Etchant 100</td><td>Transfene Company, Inc.</td><td>N/A</td><td>N/A</td></tr><tr><td>CE-5 M Chromium Mask Etchant</td><td>Transfene Company, Inc.</td><td>N/A</td><td>N/A</td></tr><tr><td>Atomic Layer Deposition System</td><td>Cambridge Nano Tech inc.</td><td>N/A</td><td>Savannah series</td></tr><tr><td>Ion Mill Etching System</td><td>Intlvac Thin Film</td><td>N/A</td><td>Nanoquest series</td></tr><tr><td>Ultrasonic Cleaner</td><td>Crest Ultrasonics</td><td>N/A</td><td>Powersonic series</td></tr><tr><td>Hydrofluoric Acid</td><td>Sigma-Aldrich</td><td>244279</td><td>Diluted to 5%</td></tr><tr><td>Field Emission Gun Scanning Electron Microscope</td><td>Jeol Ltd.</td><td>N/A</td><td>JEOL 6700 series</td></tr></tbody></table>

fabrication of nanopillar-based split ring resonators for displacement current mediated resonances in terahertz metamaterials

Terahertz (THz) anel de divisão ressonador (SRR) metamateriais (MMS) foi estudado para o gás, química e aplicações de detecção biomolecular porque o SRR não é afetado por características ambientais, como a temperatura ea pressão em torno do ressonador. A radiação electromagnética em frequências THz é biocompatível, que é uma condição crítica especialmente para a aplicação da detecção biomolecular. No entanto, o fator de qualidade (Q-Factor) e as respostas de base ressonador tradicional anel de divisão de película fina de frequência (SRR) MMs são muito baixos, o que limita as suas sensibilidades e selectividade como sensores. Neste trabalho, os novos MMs SRR baseada nanopillar, utilizando corrente de deslocamento, são projetados para aumentar o fator Q até 450, o que é cerca de 45 vezes maior que a do MMs tradicionais baseadas em thin-film. Além disso para o factor Q reforçada, o MMS baseada nanopillar induzir uma deslocamentos de frequência maiores (17 vezes em comparação com o deslocamento obtida pela tradiçãoal thin-film MMs base). Por causa das Q-fatores significativamente melhoradas e deslocamentos de frequência, bem como a propriedade da radiação biocompatível, o THz SRR baseada nanopillar são MMs ideais para o desenvolvimento de sensores biomoleculares com alta sensibilidade e seletividade sem induzir danos ou distorção de biomateriais. Um novo processo de fabricação tenha sido demonstrado para construir os SRR-base nanopillar para MMS THz corrente de deslocamento mediadas. Um (Au) galvanoplastia processo de duas etapas de ouro e de um processo de deposição de camada atómica (ALD) são usadas para criar aberturas sub-10 nm de escala entre o Au nanopillars. Uma vez que o processo é um processo de ALD revestimento isolante, um óxido de alumínio uniforme (Al 2 O 3) camada com espessura à escala nanométrica pode ser alcançado. Por galvanoplastia sequencialmente outra película fina Au para preencher os espaços entre Al 2 O 3 e Au, um repleto de perto Au-Al 2 O 3 -au estrutura com nano-escala Al 2 O 3 lacunas pode serfabricado. O tamanho dos nano-lacunas pode ser bem definida ao controlar com precisão os ciclos de deposição do processo ALD, que tem uma precisão de 0,1 nm.

<html> Esquemas de fabrico de mostrar cada etapa (Figura 2A-X). Imagens ópticas (Figura 2a-AC) e imagens de microscópio eletrônico de varredura (SEM) (Figura 2AD-AG) foram coletadas para os SRR baseada nanopillar em diferentes etapas de fabricação. As animações (Figura 2A-C) ilustram a primeira camada de Au nanopillars galvanizados e a segunda camada de Au filmes galvanizados, bem como os nano-lacunas criadas entre...

Watch this Scientific Journal Video about Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials at JoVE.com

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

Um protocolo para a concepção e fabricação de um novo ressonador anel de divisão com base em nanopillar (SRR) é apresentado.

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 ...

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7.7K visualizações.  University of Minnesota.  Um protocolo para a concepção e fabricação de um novo ressonador anel de divisão com base em nanopillar (SRR) é apresentado. 

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

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

Fabricação de Sílica Ultra microresonators alto fator de qualidade

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

Engenharia

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

Os metamateriais usando o método de fabricação Desenho de Fibra

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

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 ...

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 ...

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 ...

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

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on photoconduction, which has been one of the most commonly used techniques for terahertz generation 1-8. Terahertz generation in a photoconductive emitter is achieved by pumping an ultrafast photoconductor with a pulsed or heterodyned laser illumination. The induced photocurrent, which follows the envelope of the pump laser, is routed to a terahertz radiating antenna connected to the photoconductor contact electrodes to generate terahertz radiation. Although the quantum efficiency of a photoconductive emitter can theoretically reach 100%, the relatively long transport path lengths of photo-generated carriers to the contact electrodes of conventional photoconductors have severely limited their quantum efficiency. Additionally, the carrier screening effect and thermal breakdown strictly limit the maximum output power of conventional photoconductive terahertz sources. To address the quantum efficiency limitations of conventional photoconductive terahertz emitters, we have developed a new photoconductive emitter concept which incorporates a plasmonic contact electrode configuration to offer high quantum-efficiency and ultrafast operation simultaneously. By using nano-scale plasmonic contact electrodes, we significantly reduce the average photo-generated carrier transport path to photoconductor contact electrodes compared to conventional photoconductors 9. Our method also allows increasing photoconductor active area without a considerable increase in the capacitive loading to the antenna, boosting the maximum terahertz radiation power by preventing the carrier screening effect and thermal breakdown at high optical pump powers. By incorporating plasmonic contact electrodes, we demonstrate enhancing the optical-to-terahertz power conversion efficiency of a conventional photoconductive terahertz emitter by a factor of 50 10.

We describe methods for the design, fabrication, and experimental characterization of plasmonic photoconductive emitters, which offer two orders of magnitude higher terahertz power levels compared to conventional photoconductive emitters.

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 ...

Implementation of a Reference Interferometer for Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system&#8217;s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events.

A reference interferometer technique, which is designed to remove undesirable laser jitter noise for nanodetection, is utilized for probing an ultra-high quality factor microcavity. Instructions for assembly, setup, and data acquisition are provided, alongside the measurement process for specifying the cavity quality factor.

Implementação de um interferômetro de Referência para Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing ...

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

Utilização de Nanoestruturas Cristal plasmônicos e Fotônica para Manipulação de Micro-e Nanopartículas melhorada

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

Bioengenharia

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 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 ...