Este material está basado en trabajo apoyado por un fondo de la puesta en marcha de la Universidad de Minnesota, Twin Cities. Las partes de este trabajo se llevaron a cabo en el Centro de Caracterización de la Universidad de Minnesota, un miembro de la NSF-financiado Investigación de Materiales Instalaciones de red (www.mrfn.org) a través del programa MRSEC. Una parte de este trabajo también se llevó a cabo en el Centro de Nano Minnesota, que recibe el apoyo parcial de la NSF a través del programa NNCI.

Precaución: Varios de los productos químicos utilizados en estas síntesis son tóxicos, altamente inflamable, y puede causar irritación y daños graves a los órganos cuando se toca o se inhala. Por favor, llevar equipo de protección personal adecuado (PPE) al manejar. 1. Preparación de la primera capa de oro (Au) nanopilares matrices (Figura 2a-c y la Figura 2e-g) <ol><li> Preparación de cobre (Cu) capas de semillas para Au galvanoplastia (Figura 2A, B y la Figura 2e, f) <ol><li> Utilice una oblea de 4 &quot;de silicio de alta resistividad (Si). (Resistividad: 560-840 Ω · cm) como sustrato La oblea de Si es de tipo N dopado y pulido en un lado (Figura 2A, e). </li><li> Cortar la oblea de Si en 2 cm x piezas de 2,5 cm para su uso posterior. </li><li> Depositar una capa de 5 nm de cromo (Cr) en la muestra Si el uso de un haz de electrones (E-beam) proceso de evaporación como una capa de adhesión entre el Si y Cu. </li><li> Depositar una capa de Cu 10 nm en la parte superior de la capa de Cr existente utilizando unaE-beam proceso de evaporación como la capa de semilla para Au galvanoplastia (Figura 2b, f). </li></ol></li><li> Galvanoplastia la matriz Au nanopilares (Figura 2c, g) <ol><li> Modelando la matriz nanopilares <ol><li> Girar fotoprotector capa en la muestra preparada en el apartado 1.1 a 2.000 rpm durante 60 s. </li><li> Hornear la muestra sobre una placa caliente a 115 ° C durante 60 s. </li><li> Exponer el fotorresistente bajo luz ultravioleta (UV) -luz (poder de ~ 15 mW / cm 2) con una fotomáscara Cr que contiene miles de patrones nanopilares durante 22 s. </li><li> Desarrollar con un revelador durante 90 s con agitación. </li><li> Enjuagar la muestra con agua desionizada (DI) y el brushing la muestra con una pistola de aire. </li></ol></li><li> Galvanoplastia la matriz Au nanopilares <ol><li> Retire la sección superior de la resina fotosensible en la muestra con acetona para exponer la capa de semilla de Cu para la conexión de electrodos. </li><li> Conectar el samPLE (capa de siembra Cu) al terminal negativo de una fuente de metros con una abrazadera y un cable. En este caso, la muestra es el ánodo durante el proceso de galvanoplastia. </li><li> Conectar un trozo de platino (Pt) recubierto Si (mismo tamaño que el de la muestra) a la terminal positiva de la fuente de metros. El PT es el cátodo durante el proceso de galvanoplastia. </li><li> Sumergir tanto el cátodo y el ánodo Pt Cu en la solución de Au galvanoplastia. Mantener los dos electrodos uno frente al otro con una distancia de ~ 1 cm. </li><li> Encender el medidor de origen y suministrar una tensión constante de 1,12 V. electrochapa Au sobre la muestra durante 8 minutos (velocidad de depósito: ~ 100 nm / min). </li><li> Enjuagar la muestra con agua DI, seguido de acetona para eliminar la resina fotosensible. </li><li> Enjuagar la muestra con agua DI otra vez y secar con secador con una pistola de aire. </li><li> Comprobación de la matriz galvanizado nanopilares Au bajo un microscopio. </li><li> Medir el espesor de la UA nanopilares con un perfilómetro (El espesor de laAu nanopilares es ~ 800 nm). NOTA: Corriente constante puesta a punto también puede ser utilizado para galvanizar Au nanopilares. Tanto en constante tensión y de corriente constante puesta a punto, la corriente y la tensión ideales utilizado para el Au galvanoplastia puede lograrse mediante ensayo y error. </li></ol></li></ol></li></ol> 2. Creación de Nano-huecos entre Au nanopilares (Figura 2d, h) <ol><li> La eliminación de capas de Cr y Cu <ol><li> Sumergir la muestra en Cu reactivo de ataque hasta que el color desaparece Cu. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li><li> Inspeccionar las Au nanopilares bajo un microscopio. </li><li> Sumergir la muestra en Cr máscara reactivo de ataque durante 10 s. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li><li> Inspeccionar las Au nanopilares bajo un microscopio. </li></ol></li><li> La fabricación de óxido de aluminio a escala nanométrica (Al 2 O 3) huecos <ol><li> Calentar el sistema ALD ChamBER a 200 ° C. </li><li> Colocar la muestra en el centro de la cámara. </li><li> Evacuar la cámara a un vacío y establecer el número de ciclos a 100 (velocidad de depósito: ~ 1 A / ciclo). </li><li> Secuencial y alternativamente pulsos de gas trimetilaluminio (TMA) con un periodo de tiempo de 0,015 s y agua (H2O) de vapor con un período de tiempo de 0,015 s en la cámara para depositar uniformemente Al 2 O 3 capas en la muestra. El intervalo de tiempo entre cada pulso es de 5 s. La presión de la cámara durante el impulso TMA es de 10 Torr y la presión durante el H 2 O pulso de vapor es de 2 Torr. </li><li> Purgar y el vacío de la cámara entre cada ciclo de la deposición. Depósito de Al 2 O 3 para 100 ciclos y sacar la muestra de la cámara. </li><li> Medir el espesor de la ALD Al 2 O 3 usando un elipsómetro. </li></ol></li></ol> 3. Preparación de la segunda capa de Au de película delgada (Figura 2i-l y la Figura 2m-p) <ol><li> Preparación de capas de semillas para Cu Au galvanoplastia (Figura 2i, m) <ol><li> Colocar la muestra en el centro de un soporte de muestras del evaporador de haz de electrones. </li><li> Desactivar la rotación de la muestra en el evaporador de haz de electrones. </li><li> Depositar una capa de Cr 5 nm sobre la muestra para actuar como una capa de adhesión entre Al 2 O 3 y Cu. Utilice un proceso de evaporación por haz de electrones, sin rotación de la muestra. </li><li> Depósito 10 nm Cu en la parte superior de la capa de Cr existente mediante un proceso de evaporación de haz de electrones sin rotación de la muestra como la capa de semilla para Au galvanoplastia. </li></ol></li><li> Galvanoplastia la película delgada de Au (Figura 2j, n) <ol><li> Conectar la muestra (capa de siembra Cu) al terminal negativo de la fuente de metros con una abrazadera y un cable. En este caso, la muestra es el ánodo durante el proceso de galvanoplastia. </li><li> Conectar el cátodo Pt al terminal positivo de la fuente de metros. </li><li> Sumergir tanto el cátodo Pt y Cu anode en la solución de Au galvanoplastia. Mantener los dos electrodos uno frente al otro con una distancia de ~ 1 cm. </li><li> Encender el medidor de origen y configura voltaje constante de 1,35 V y electroplate Au sobre la muestra durante 16 min. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li><li> Inspeccionar el Au galvanizado y la matriz previamente galvanizado nanopilares Au bajo un microscopio. </li><li> Medir el espesor de la UA nanopilares con un perfilómetro (espesor de la UA nanopilares es de ~ 400 nm). NOTA: Al igual que en el Au galvanoplastia en la sección 1.2.2, corriente constante puesta a punto también puede ser utilizado para galvanizar Au película delgada. Tanto en constante tensión y de corriente constante puesta a punto, la corriente y la tensión ideales utilizado para el Au galvanoplastia puede lograrse mediante ensayo y error. </li></ol></li><li> La eliminación de capas de Cr y Cu (Figura 2 k, o) <ol><li> Sumergir la muestra en Cu reactivo de ataque durante 10 s. </li><li> Enjuagar la muestra con un DI de aguad-golpe seco con una pistola de aire. </li><li> Inspeccionar las Au nanopilares bajo un microscopio. </li><li> Sumergir la muestra en Cr máscara reactivo de ataque durante 10 s. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li><li> Inspeccionar las Au nanopilares bajo un microscopio. NOTA: Como alternativa, sumergir la muestra en solución Au galvanoplastia de nuevo para depositar una capa adicional de Au en la parte superior de la segunda capa de Au galvanizado después de la eliminación de Cr y Cu (paso 3.3). Este Au capa adicional aumenta el espesor total de la segunda capa de Au y asegura un buen contacto entre la capa de Au y la capa de Al 2 O 3 (Figura 2i, p). </li></ol></li></ol> 4. Definición de SRR en forma de C (figura 2q-s y la figura 2u-w) <ol><li> Modelando la SRR en forma de C (Figura 2 q, u) <ol><li> Girar capa una resina fotosensible en la muestra a 2000 rpm durante 60 s. </li><li> Hornear la muestra en la placa caliente de 115 ° C durante 60 s. </li><li&gt; Expongo fotoprotector con luz ultravioleta (poder de ~ 15 mW / cm2) con una fotomáscara Cr durante 22 s. </li><li> Desarrollar con un revelador durante 90 s con agitación. </li><li> Enjuagar la muestra con agua DI y el brushing la muestra con una pistola de aire. </li></ol></li><li> Definición en forma de C utilizando molino de iones (Figura 2R, V y Figura 2 s, w) <ol><li> Coloque la muestra sobre un soporte de muestra de la fábrica de iones usando una cinta conductora de doble cara Cu. </li><li> Enfriar la cámara del molino de iones a 6 ° C. </li><li> Ion molino de la muestra con un voltaje del haz de 300 V y una corriente del haz de 125 mA durante ~ 30 min. </li><li> Sacar la muestra e inspeccionar los Au nanopilares fuera de la forma de C. </li><li> Repita el paso 4.2.3 y 4.2.4, si Au es todavía visible fuera de la forma de C. </li><li> Sonicar la muestra en acetona para eliminar la resina fotosensible. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li><li> Inspeccionar la muestra bajo un microscopio. </li><li> Repita el paso 4.2.6 y 4.2.7 si fotoprotector no se elimina totalmente. NOTA: Como alternativa, aplicar oxígeno resisten ablandamiento pasos para la fotoprotección antes de retirar la resina fotosensible. Sin embargo, un baño de ultrasonidos es el método más eficaz para eliminar fotorresistente si procede. </li></ol></li></ol> 5. Eliminación de Al 2 O 3 para el aire Nano-lagunas (Figura 2t, x) <ol><li> Sumergir la muestra en solución al 5% de fluoruro de hidrógeno (HF) durante 5 minutos para eliminar Al 2 O 3. </li><li> Enjuagar la muestra con agua desionizada y secar con secador con una pistola de aire. </li></ol>

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Esta técnica de fabricación tiene ventajas significativas para la creación de estructuras a escala nanométrica sobre los métodos existentes, tales como la litografía por haz de electrones y la auto-ensamblaje. En primer lugar, las estructuras de escala nanométrica se pueden realizar sobre un área grande (toda una oblea), utilizando una fotomáscara que cuenta con arrays nanopilares, que no es práctico con un proceso de litografía por haz de electrones. En segundo lugar, el proceso de fabricación utiliza un pr...

Terahertz (THz) metamateriales (MMS) se han desarrollado para sensores biomédicos y dispositivos 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 de frecuencia ágil. Con el fin de mejorar la sensibilidad y la frecuencia de la selectividad de los THz sensores mm, una basada en nanopilares anillo partido resonador (SRR) se ha diseñado utilizando la corriente de desplazamiento generado en el interior de oro (Au) matrices nanopilares para excitar resonancias THz con factores de ultra alta calidad ( factores Q) (~ 450) (Figura 1) 12. A pesar de que las RSR basada en nanopilares muestran altos factores Q y capacidades de detección prometedores, fabricación de tales nanostructurí con altas relaciones de aspecto (más de 40) y las lagunas de nano escala (sub-10 nm) en una amplia zona sigue siendo un reto 13. La técnica más utilizada para fabricar estructuras a escala nanométrica es la litografía por haz de electrones (EBL) 14, 15, 16, 17. Sin embargo, la resolución de EBL está todavía limitada debido a el tamaño del punto del haz, la dispersión de electrones, las propiedades de la capa protectora, y el proceso de desarrollo 18, 19. Además, no es práctico para la fabricación de nanoestructuras usando EBL en una gran superficie debido a un tiempo de proceso lento y cuesta gran proceso 20. Otra estrategia para lograr nanoestructuras es utilizar una técnica de auto-ensamblaje 21, 22. Por nanocubos de metal de autoensamblaje (CN) en una solución y utilizing la interacción electrostática y la asociación de ligandos poliméricos entre los CN, una matriz unidimensional NC bien organizado, con lagunas de nano escala se puede lograr 23. El tamaño nano-gap depende de los ligandos de polímero entre los CN y puede ser controlado mediante la aplicación de diferentes materiales poliméricos con diferentes pesos moleculares 24, 25, 26. El autoensamblaje es una poderosa técnica para el logro de nanoestructuras escalables y rentables 23. Sin embargo, el proceso de fabricación es más complicado en comparación con los procesos de micro y nano de fabricación convencionales, y el control de los tamaños de nano-GAP no es suficientemente precisa para aplicaciones de dispositivos electrónicos. Con el fin de fabricar con éxito SRR basada en nanopilares, un nuevo método de fabricación deben ser inventó para lograr los siguientes objetivos: i) el proceso de fabricación es fácil de aplicar y es compatible con la convenciónmicro y nano fabricación de procesos al; ii) la fabricación en una gran superficie es aplicable; iii) tamaños nano-gap pueden ser controlados fácilmente y con precisión con una resolución de 0,1 nm y se pueden escalar hasta 10 nm o menos. Un nuevo método de fabricación se demuestra mediante la combinación de un proceso de galvanoplastia y un proceso de deposición atómica capa (ALD) para fabricar SRR basado en nanopilares. Desde galvanoplastia es un proceso de auto-llenado de bajo costo, es fácil de fabricar estructuras sobre un área grande. ALD es un proceso de deposición química de vapor (CVD) que puede ser controlada con precisión por el ciclo de reacción durante el proceso. La resolución de película delgada puede ser ALD 0,1 nm, y la película delgada se recubre uniformemente con una alta calidad, que es adecuado para crear vacíos nano-escala de 27, 28. array SRR basado en nanopilares con 10 lagunas nm o menos se puede fabricar con éxito en un área de 6 mm x 6 mm. ambos sLos espectros de transmisión THz imulated y medidos muestran comportamientos resonantes con ultra-alta Q-factores y grandes cambios de frecuencia, lo que demuestra la viabilidad de las SRR basada en nanopilares mediadas por la corriente de desplazamiento. El proceso de fabricación detallado se describe a continuación en la sección de protocolo y el protocolo de vídeo puede ayudar a los médicos a comprender el proceso de fabricación y evitar errores comunes asociados con la fabricación de las RSR basada en nanopilares.

<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) resonador anillo partido (SRR) metamateriales (MMS) se ha estudiado para el gas, productos químicos, y aplicaciones de detección biomoleculares porque el SRR no se ve afectada por las características ambientales, como la temperatura y la presión que rodea el resonador. La radiación electromagnética en las frecuencias de THz es biocompatible, lo que es una condición crítica, especialmente para la aplicación de la detección biomolecular. Sin embargo, el factor de calidad (factor Q) y las respuestas de frecuencia del resonador de anillo partido basado en película fina tradicional (SRR) MM son muy bajos, lo que limita su sensibilidad y selectividad como sensores. En este trabajo, nuevos MM-SRR basado nanopilares, utilizando corriente de desplazamiento, están diseñados para mejorar el factor Q hasta 450, que es de alrededor de 45 veces mayor que la de los MM tradicionales basados ​​en película delgada. Además del factor Q mayor, los MMs a base de inducir una nanopilares cambios de frecuencia más grandes (17 veces en comparación con el desplazamiento obtenido por la tradiciónal MM a base de película delgada). Debido a los factores Q mejoradas significativamente y cambios de frecuencia, así como la propiedad de la radiación biocompatible, el SRR basada en nanopilares THz son MMS ideales para el desarrollo de sensores biomoleculares con alta sensibilidad y selectividad, sin ocasionar daños o distorsión de los biomateriales. Un nuevo proceso de fabricación se ha demostrado para construir los SRR basado en nanopilares para MMS THz mediadas corriente de desplazamiento. A dos pasos de oro (Au) proceso de galvanoplastia y un proceso de deposición de capa atómica (ALD) se utilizan para crear vacíos sub-10 nm escala entre Au nanopilares. Dado que el proceso es un proceso ALD revestimiento de conformación, un óxido de aluminio uniforme (Al 2 O 3) capa con espesor a escala nanométrica puede ser alcanzado. Por galvanoplastia secuencialmente otra película delgada de Au para llenar los espacios entre Al 2 O 3 y Au, una de empaquetamiento compacto Au-Al 2 O 3 -Au estructura con nano-escala de Al 2 O 3 lagunas pueden serfabricado. El tamaño de las nano-huecos puede estar bien definida controlando con precisión los ciclos de deposición del proceso de ALD, que tiene una precisión de 0,1 nm.

<html> Esquemas de fabricación muestran cada paso (Figura 2a-x). Se recogieron imágenes ópticas (Figura 2a-ac) y microscopio electrónico de barrido (SEM) imágenes (Figura 2AD-ag) para las SRR basada en nanopilares en diferentes etapas de fabricación. Animaciones (Figura 2a-c) ilustran la primera capa de Au nanopilares galvánico y la segunda capa de películas de Au galvanizadas, así como los nano-vacíos creados e...

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

Se presenta un protocolo para el diseño y fabricación de un nuevo resonador de anillo partido basado en nanopilares (SRR).

La fabricación de resonadores de anillo partido basadas en nanopilares para la corriente de desplazamiento mediadas resonancias en terahercios metamateriales

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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Unit 1

Electromagnetic Induction

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7.7K vistas.  University of Minnesota.  Se presenta un protocolo para el diseño y fabricación de un nuevo resonador de anillo partido basado en nanopilares (SRR). 

Video: 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.

La fabricación de sílice de alta calidad Ultra microresonators Factor

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

Investigación

Ingeniería

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.

Los metamateriales Fabricacion mediante el método de dibujo 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

Terahertz microfluídicos detección utilizando un sensor de guía de ondas 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.

Simulación, Fabricación y Caracterización de THz Amortiguadores metamateriales

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.

Microondas Fotónica sistemas basados ​​en resonadores-gallery-mode 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.

Diseño, Fabricación y Caracterización Experimental de Plasmónicos Emisores terahercios fotoconductoras

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.

Implementación de un interferómetro de referencia 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.

Utilización de nanoestructuras fotónicas de cristal plasmónicos y para la manipulación mejorada de Micro y nanopartículas

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

Bioingeniería

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.

Fabricación y caracterización de resonadores superconductores

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.

La fabricación de 1-D de cristal fotónico cavidad en un nanofibras Uso de ablación inducida por láser de femtosegundo

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

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