Los autores desean agradecer a Picometrix para proporcionar el sustrato LT-GaAs y agradecen el apoyo financiero de Michigan Espacio Beca Consorcio, DARPA Premio Joven Facultad dirigido por el Dr. John Albrecht (contrato # N66001-10-1-4027), NSF CARRERA Premio dirigido por el Dr. Samir El-Ghazaly (contrato # N00014-11-1-0096), ONR Premio Joven Investigador dirigido por el Dr. Paul Maki (contrato # N00014-12-1-0947), y ARO Premio Joven Investigador gestionado por Dr. Dev. Palmer (contrato # W911NF-12-1-0253).

1. Plasmónicas Fabricación emisor Photoconductive <ol><li> Fabrique rejillas plasmónica. <ol><li> Limpiar la oblea de semiconductor mediante la inmersión en acetona (2 min) seguido de isopropanol (2 min), y aclarado con agua desionizada (10 seg). </li><li> Secar la muestra con nitrógeno y se calienta en una placa caliente a 115 ° C durante 90 segundos para eliminar cualquier resto de agua. </li><li> Spin MicroChem 950K PMMA A4 en la muestra a 4000 rpm durante 45 seg. Pre-hornear la resisten en una placa caliente a 180 ° C durante 3 min. </li><li> Coloque la muestra en una herramienta de litografía por haz de electrones (JEOL JBX-6300-FS). Exponer el patrón de rejilla plasmónica a una dosis base alrededor de 650 mC / cm 2, con un voltaje de aceleración de 100 kV. </li><li> Desarrollar PMMA mediante la inmersión de la muestra en un MIBK: IPA mezcla 01:03 de 90 seg. Inmediatamente la transferencia de la muestra a una solución de isopropanol puro para 60 seg. </li><li> Lavar la muestra con agua desionizada durante 10 segundos y después secar la muestra con nitrógeno. </li><li> Coloque la muestra en un separador de plasma (YES-CV200RFS). Descum la muestra con 30 W de potencia de RF a 30 ° C con una velocidad de flujo sccm O 100 2 durante 10 s. </li><li> Eliminar de óxido superficial mediante la inmersión en una HCl: H 2 0 03:10 mezcla durante 30 seg. Inmediatamente la transferencia de la muestra a una cascada de enjuague de agua desionizada durante 4 min. </li><li> Transferir la muestra a un vaso de precipitados de agua desionizada para reducir al mínimo la exposición al oxígeno atmosférico antes de la deposición de metal. </li><li> Tome vaso de precipitados que contiene la muestra en agua desionizada a un evaporador de metal (Denton SJ-20). Purgar la cámara y retire, seque, y cargar la muestra en la cámara (estos pasos se deben seguir sin interrupción para evitar la formación de óxido de la superficie de la muestra). </li><li> Bombear la cámara a una presión por debajo de 2x10 -6 Torr. Depósito Ti / Au (50/450). </li><li> Purgar la cámara y retire la muestra. </li><li> Para el despegue del metal depositado, coloque la muestra en un soporte de Teflon en unvaso de acetona, cubrir y dejar toda la noche. Destape el vaso, colocarlo en un agitador ultrasónico, y esperar hasta que se retire todo el metal no deseado (normalmente 30 segundos). </li></ol></li><li> Depósito de pasivación de SiO 2. <ol><li> Limpie la muestra que en los pasos 1.1.1 - 1.1.2. </li><li> Cargar la muestra en una herramienta de deposición de vapor químico mejorada por plasma (PECVD GSI). Depósito 1500 Å de SiO2 a 200 ° C. </li></ol></li><li> Abrir vías de contacto a través de SiO2. <ol><li> Limpie la muestra que en los pasos 1.1.1 - 1.1.2. </li><li> Haga girar el HMDS a 4.000 rpm durante 30 segundos. Haga girar el Megaposit SPR 220 a 3,0 fotoprotector a 4.000 rpm durante 30 segundos. Pre-hornear la resisten en una placa caliente a 115 ° C durante 90 segundos. </li><li> Cargue la muestra y la placa de máscara en la litografía de proyección paso a paso (GCA autostep 200). Alinear la muestra y exponer. </li><li> Post-hornear el fotorresistente expuesto en una placa caliente a 115 ° C durante 90 seg. </li><li> Desarrollar resistir AZ 300 MIF desarrollador de 60 seg. </li><li> Inmediatamente mover la muestra a una cascada de aclarado de agua desionizada durante 4 min. Secar la muestra con nitrógeno. </li><li> Coloque la muestra en un grabador iones reactivos (LAM 9400). Etch SiO2 utilizando una fuente de TCP RF de 500 W, una potencia RF Sesgo de 100 W, 15 sccm de SF6, 50 sccm de C 4 F 8, 50 sccm de Él, 50 sccm de Ar durante 80 seg. </li><li> Eliminar la mayor parte de la resina fotosensible mediante la colocación de la muestra en acetona (5 min) seguido de isopropanol (2 min). Enjuague con agua desionizada (10 seg.) Secar con nitrógeno. </li><li> Retire el fotoprotector residual cargando la muestra en una bailarina de striptease plasma (YES-CV200RFS). Retire el fotoprotector con 800 W de potencia de RF a 30 ° C con un caudal sccm O 100 2 de 5 min. </li></ol></li><li> Fabrique antenas y líneas de polarización. <ol><li> Repita los pasos 1.3.1 - 1.3.6 para antenas de patrones y líneas de polarización. </li><li> Repita los pasos 1.1.8 - 1.1.9 para eliminar el óxido superficial. </li><li> Tome el vaso de precipitados que contiene la muestra yagua desionizada a un evaporador de metal (Denton SJ-20). </li><li> Purgar la cámara y retire rápidamente, secar, y cargar la muestra en la cámara. </li><li> Bombear la cámara a una presión por debajo de 2x10 -6 Torr. Depósito Ti / Au (10/4, 000 Å). </li><li> Purgar la cámara y retire la muestra. </li><li> Repita el paso 1.1.13 para el despegue del metal depositado. </li></ol></li><li> Empaquete la muestra. <ol><li> Pegamento de los bordes de un mm de diámetro de la lente de silicio hiper-hemisférica 12 a una lavadora de aluminio de 2 pulgadas con el agujero de 8 mm. </li><li> Pegue una placa PCB con restos de metal, a la cual se puede fácilmente la soldadura, la arandela de aluminio. </li><li> Monte los plasmónicas fotoconductoras prototipos emisor terahercios fabricados en la lente de silicio utilizando epoxi fina. </li><li> Bonos de alambre las zonas de contacto del dispositivo a una tarjeta de circuito impreso pegado en la misma lavadora de aluminio. </li><li> Soldar los cables a los rastros de metal en la placa PCB. </li><li> Conectar almohadillas de contacto del dispositivo a un analizador paramétrico (Hewlett Paqueteard 4155A) con cables soldados a las almohadillas correspondientes de la placa PCB para realizar pruebas. </li></ol></li></ol> 2. Plasmónicas Caracterización emisor Photoconductive <ol><li> Alineación de dispositivos. <ol><li> Coloque la arandela de aluminio que lleva los fotoconductores plasmónica de terahercios prototipos emisor en un montaje rotación y firmemente enfocar la bomba óptica de un Ti: Zafiro modo-cerró láser (MIRA 900D V10 XW OPT 110V) en el área activa de cada dispositivo. </li><li> Ajustar el montaje de rotación de tal manera que el campo eléctrico de la bomba óptica está orientada para la excitación eficiente de las ondas de plasmón de superficie (normal a las rejillas plasmónica). </li><li> Utilice el analizador paramétrico para, simultáneamente, aplicar voltajes de polarización para cada dispositivo y medir la corriente eléctrica inducida en cada dispositivo. Confirme la alineación de la bomba óptica óptima y el ajuste de polarización mediante la maximización de la fotocorriente de cada dispositivo bajo prueba. </li></ol></li><li> Medición de potencia de salidadición. <ol><li> Use un interruptor óptico (Thorlabs MC2000) para modular la bomba óptica del modo bloqueado incidente láser de bombeo en cada dispositivo. </li><li> Medir la potencia de salida de los prototipos emisor terahercios fotoconductoras plasmónicas utilizando un detector piroeléctrico (Detector Spectrum, Inc. SPI-A-65 THz). </li><li> Conectar la salida del detector piroeléctrico a un amplificador lock-in (Sistemas de Investigación Stanford SR830) con la frecuencia de referencia del helicóptero óptica para recuperar los datos de potencia de terahercios a bajos niveles de ruido. </li></ol></li><li> Caracterización espectral de la radiación. <ol><li> Comenzar con un Ti: Zafiro láser de modo bloqueado y utilizar un divisor de haz para dividir la salida del láser de modo bloqueado en un haz de la bomba y un haz de sonda. </li><li> Utilice un modulador electro-óptico (EO Thorlabs-AM-NR-C2) para modular el haz óptico en la trayectoria de la bomba. Enfocar el haz de la bomba en el área activa del emisor fotoconductora bajo prueba para generar la radiación de terahercios. </li><li> Colimael haz de terahercios generado utilizando una primera lente esférica de polietileno. Enfoque el haz colimado terahercios utilizando una segunda lente esférica polietileno. </li><li> Antes de que el foco del haz de terahercios, combinar el haz colimado de terahercios con el haz óptico de sonda usando un filtro de vidrio recubierto con ITO. </li><li> Coloca un 1 mm de espesor, &lt;110&gt; cristal CnTe montado en una etapa de rotación en el enfoque combinado del haz óptico y de terahercios. </li><li> Insertar una línea óptica de retardo controlable en la trayectoria de la sonda óptica mediante el uso de una etapa lineal motorizado (Thorlabs NRT100) para variar el retardo de tiempo entre los pulsos ópticos y de terahercios que interactúan dentro del cristal CnTe. </li><li> El uso de un medio-placa de onda en la trayectoria de la sonda, rotar la polarización de la sonda óptica para estar en un ángulo de 45 ° con respecto a la dirección de polarización de terahercios. </li><li> Use un cuarto de placa de onda después de que el cristal CnTe, convierte la polarización del haz óptico en la polarización circular. </li><li> Dividir la circulhaz óptico arly polarizada en dos ramas por un prisma Wollaston. Medir la potencia del haz óptico en cada rama usando dos detectores equilibrados conectados a un amplificador lock-in. </li><li> Conecte la línea de retardo motor y amplificador lock-in a un ordenador. Escribir un guión de Matlab para moverse iterativamente la posición de la línea de retardo motor, hacer una pausa, y leer la magnitud de la señal desde el amplificador lock-in. </li><li> Convertir la posición de fase para el dominio del tiempo, a través de la división de la longitud total óptica de retardo por la velocidad de la luz, seguido de una transformada de Fourier discreta (con Matlab) para obtener los datos de dominio de la frecuencia. </li></ol></li></ol>

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Y., Wang, N., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+Ultrafast+Pump-Probe+Measurements+at+the+Nanoscale.+Special+Issue+of+"Optics+in+2011.">Toward Ultrafast Pump-Probe Measurements at the Nanoscale. Special Issue of "Optics in 2011.</a> Optics &amp; Photonics News. 22, (2011).</li><li>Hsieh, B. -. Y., Jarrahi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+focusing+of+terahertz+and+optical+waves+into+nano-scale.">Simultaneous focusing of terahertz and optical waves into nano-scale.</a> Proc. Int. Conf. Infrared, Millimeter, and Terahertz Waves. , 1-2 (2011).</li><li>Jackson, A. W., Ibbetson, J. P., Gossard, A. C., Mishra, U. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+thermal+conductivity+in+low-temperature+grown+GaAs.">Reduced thermal conductivity in low-temperature grown GaAs.</a> Appl. Phys. Lett. 74, 2325-2327 (1999).</li></ol>

No hay conflictos de interés declarado.

En este artículo de vídeo, se presenta una técnica de generación de terahercios fotoconductora novedoso que utiliza una configuración de electrodo de contacto plasmónica para mejorar la eficiencia de conversión óptica-a-terahercios por dos órdenes de magnitud. El aumento significativo de la potencia de radiación de terahercios desde los emisores fotoconductoras plasmónicas presentados es muy valiosa para el futuro de alta sensibilidad de terahercios formación de imágenes, la espectroscopia y sistemas de esp...

Nosotros presentamos un nuevo emisor de terahercios fotoconductora que utiliza una configuración de electrodo de contacto plasmónica para mejorar la eficiencia de conversión óptica-a-terahercios por dos órdenes de magnitud. Nuestra técnica se ocupa de las limitaciones más importantes de emisores convencionales fotoconductoras terahertz, es decir, bajo la producción de energía y la escasa eficiencia de energía, que se originan a partir de la compensación inherente entre la alta eficiencia cuántica y operación ultrarrápida de fotoconductores convencionales. Una de las novedades clave en nuestro diseño que llevaron a esta mejora de rendimiento a saltos es el diseño de una configuración de electrodo de contacto que se acumula un gran número de portadores foto-generados en las proximidades de los electrodos de contacto, de manera que puedan ser recogidos dentro de un sub- picosegundo calendario. En otras palabras, la solución de compromiso entre la operación ultrarrápida fotoconductor y alta eficiencia cuántica se mitiga por la manipulación espacial de la foto-génerosportadores Ted. Electrodos de contacto Plasmónicos ofrecen esta capacidad única de (1) que permite el confinamiento de luz en áreas activas de dispositivos a nanoescala entre los electrodos plasmónicas (más allá del límite de difracción), (2) mejora extraordinaria luz al contacto de metal y foto-absorción de la interfaz semiconductor 10, 11. Otro atributo importante de nuestra solución es que tiene capacidad para grandes áreas activas del fotoconductor sin un aumento considerable de la carga parasitaria a la antena radiante de terahercios. La utilización de grandes áreas activas fotoconductor permiten mitigar el efecto de detección de portador y la descomposición térmica, que son las limitaciones en última instancia para la potencia máxima de la radiación de emisores fotoconductoras convencionales. Este artículo de vídeo se concentra en los atributos únicos de nuestra solución presentada mediante la descripción de la física que gobierna, modelación numérica, y la verificación experimental. Se demuestra experimentalmente 50 veces más altos poderes de terahercios de una Phot plasmónicaemisor oconductive en comparación con un emisor de fotoconductora similar con electrodos de contacto no plasmónica.

<table border="1">
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</table>

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

En este artículo de vídeo se presenta una demostración detallada de un método altamente eficiente para la generación de las ondas de terahercios. Nuestra técnica se basa en fotoconducción, que ha sido una de las técnicas más utilizadas para la generación de terahertz 1-8. Generación de terahercios en un emisor de fotoconductora se logra mediante el bombeo de un fotoconductor ultrarrápido con una iluminación láser pulsado o heterodina. La fotocorriente inducida, que sigue a la envolvente de la bomba de láser, se encamina a una antena radiante de terahercios conectado a los electrodos de contacto del fotoconductor para generar la radiación de terahercios. Aunque la eficiencia cuántica de un emisor de fotoconductora puede alcanzar teóricamente 100%, las relativamente largas longitudes de trayecto de transporte de portadores foto-generados a los electrodos de contacto de fotoconductores convencionales han limitado gravemente su eficiencia cuántica. Además, el efecto de la detección de portadores y la descomposición térmica limitan estrictamente el p salida máximaower de las fuentes de terahertz fotoconductoras convencionales. Para hacer frente a las limitaciones de eficiencia cuántica de emisores de terahercios fotoconductoras convencionales, hemos desarrollado un nuevo concepto emisor fotoconductora que incorpora una configuración de electrodo de contacto plasmónica para ofrecer alta eficiencia cuántica y funcionamiento ultrarrápido simultáneamente. Mediante el uso de electrodos de contacto plasmónicas nano escala, se reduce significativamente la trayectoria de transporte portadora fotogenerada promedio de electrodos de contacto fotoconductor en comparación con fotoconductores convencionales 9. Nuestro método también permite aumentar la superficie activa del fotoconductor sin un aumento considerable de la carga capacitiva a la antena, aumentando la potencia máxima de la radiación de terahercios mediante la prevención de los efectos de detección de portador y la descomposición térmica a altas potencias de bombeo óptico. Mediante la incorporación de electrodos de contacto plasmónica, se demuestra la mejora de la eficiencia de conversión de potencia óptica-a-terahercios de un fotoconductor TE convencionalrahertz emisor por un factor de 50 10.

Para demostrar el potencial de los electrodos plasmónica para la mejora de potencia de terahercios, se han fabricado dos emisores de terahercios: un emisor fotoconductora convencional (Figura 1a) y plasmónica (Figura 1b) la incorporación de electrodos de contacto plasmónica para reducir los tiempos de transporte de portadores para ponerse en contacto con los electrodos. Ambos diseños consisten en un fotoconductor ultrarrápido con 20 micras brecha entre el ánodo y el cátodo conta...

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

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

Se describen métodos para el diseño, fabricación y caracterización experimental de los emisores fotoconductoras plasmónica, que ofrecen dos órdenes de niveles de potencia más altos terahercios magnitud en comparación con los emisores fotoconductoras convencionales.

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 ...

design-fabrication-experimental-characterization-plasmonic

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14.8K vistas.  University of Michigan. Se describen métodos para el diseño, fabricación y caracterización experimental de los emisores fotoconductoras plasmónica, que ofrecen dos órdenes de niveles de potencia más altos terahercios magnitud en comparación con los emisores fotoconductoras convencionales.

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

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

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

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

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 ...

Investigación

Ingeniería

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 ...

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

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

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

Fabricación y caracterización de guías de onda de cristal fotónico luz lenta y cavidades

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

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

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

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

Fabricación y Caracterización de Polímeros desordenados Fibras ópticas para Transversal Anderson Localización de Luz

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

Patterning via Optical Saturable Transitions - Fabrication and Characterization

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

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

Patrones través ópticos saturable Transiciones - Fabricación y Caracterización

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

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

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

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

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

La fabricación de la impresión a granel heterounión células solares y<em&gt; In Situ</em&gt; Morfología Caracterización

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

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

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

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

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

De forma libre actuadores de luz - Fabricación y Control de la Actuación en la escala microscópica

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

Fabrication and Characterization of Superconducting Resonators

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

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

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

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

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

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 ...

Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

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

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

Diseño y metodología de caracterización para filtros de MEMS Tunable eficiente toda la gama

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