Surface-Enhanced Spectroelectrochemistry using Synchrotron Infrared Radiation

Electrochemical reactions are inherently heterogeneous, occurring at the interface between a solid electrode and an electrolyte solution. Therefore, detailed mechanistic understanding requires the electrode/solution interface (ESI) to be interrogated. Doing so with spectroelectrochemical techniques generally encounters several analytical challenges. Sampling the ESI requires a surface-sensitive spectroscopy capable of addressing a buried interface, placing strong limitations on photon energy and spectroelectrochemical cell design. Furthermore, dynamic measurements are fundamentally limited by the finite rise time of the electrode. For many important processes with characteristic timescales in the milli- to microsecond regime, achieving a suitably low rise time requires the use of an electrode with critical dimensions in the hundreds of micrometers, i.e. a microelectrode. In this thesis, I develop the spectroscopic platform necessary to perform surface-sensitive, time-resolved infrared measurements in the milli- to microsecond regime. I will make the case that an infrared spectroelectrochemical technique, namely attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), is applicable because it is intrinsically surface-sensitive, yields detailed information on molecular structure, and is compatible with a range of electrocatalytic metals. I will show that the small size of the microelectrode requires an unconventional infrared source, namely highly focused synchrotron radiation. This thesis will present the characterization of a new internal reflection element which is fully compatible with ATR-SEIRAS and easily amenable to microfabrication. A custom horizontal microscope endstation will be developed at the mid-IR beamline at the Canadian Light Source. Its general utility beyond the primary goal of this thesis will be demonstrated with imaging experiments of a simple interfacial reaction in a microfluidic device. Finally, a 500 micrometer wide linear microelectrode compatible with ATR-SEIRAS will be fabricated and preliminary kinetic measurements of a model electrochemical process, namely the potential-induced desorption of 4-methoxypyridine, will be discussed

Development of a high intensity Mid-Ir OPCPA pumped by a HO:YLF amplifier

The continuous development of laser sources delivering ultra-short light pulses underpins much of the current progress in experimental science, particularly in the domain of physics concerned with strong-field phenomena. Laser systems that allow scaling of strong-field experiments to unexplored regions of the electromagnetic spectrum, specially the mid-IR range (2 µm < lambda < 20 µm), have proved to be a powerful tool enabling the study of new physical processes. It is becoming clear however, that conventional laser sources are unsuited for this purpose, and in order to fully investigate these novel regimes a new generation of laser systems is required. This thesis describes a new laser source of high-intensity, mid-IR light. A long-wavelength pumped optical parametric chirped pulse amplifier (OPCPA) design is chosen as the architecture for this laser, overcoming many of the drawbacks hindering other approaches. This thesis presents two novel sub-systems required for the successful development of a mid-IR OPCPA. The first is a compact, fibre-driven source of broadband mid-IR pulses relying on difference frequency generation (DFG) in the nonlinear crystal CdSiP2. This laser is the seed source in the OPCPA and supports transform-limited pulses corresponding to less than 3 optical cycles at the operating wavelength of 7 µm. The second sub-system is a pump source based on a Ho:YLF chirped pulse amplifier (CPA) pumped by commercial Tm-fibre laser. The pump system delivers over 0.25 J of pulse energy at a wavelength of 2052 nm. The laser system described in this thesis is a developmental milestone towards the realisation of a multi-mJ source of few-cycle duration, carrier-to-envelope phase (CEP) stable mid-IR pulses. The system is designed to operate at a centre wavelength of 7 µm, delivering pulses with an energy of 0.2 mJ and a temporal duration of 180 fs at 100 Hz repetition rate. The output parameters of the laser presented in this work lead to a peak power of 1.1 GW and potentially a peak intensity of 7·1014 W/cm2. These values are already compatible with strong-field experiments and enable a ponderomotive force 77 times larger than a standard Ti:Sapphire laser.El desarrollo de fuentes de luz láser que emiten pulsos ultracortos sustenta una parte importante del progreso actual en ciencia experimental, especialmente en el ramo de la física relacionada con los fenómenos de campo electromagnético intensos. Los sistemas láser que permiten escalar experimentos de campo electromagnético intenso a regiones sin explorar del espectro electromagnético, especialmente en el rango del infra-rojo medio (2 µm < lambda < 20 µm), han demostrado ser una poderosa herramienta facilitando el estudio de nuevos procesos físicos. Sin embargo, las fuentes láser convencionales no son adecuadas para este propósito, y para investigar a fondo estos nuevos regímenes se requiere una nueva generación de sistemas láser. Esta tesis describe una nueva fuente láser de luz de infra-rojo medio de alta intensidad. La arquitectura que elegimos es un amplificador de pulso óptico dispersado paramétrico (OPCPA por sus siglas en inglés) bombeado con una longitud de onda larga y superando así muchos de los inconvenientes de otros diseños. Esta tesis presenta dos sub-sistemas nuevos necesarios para el desarrollo exitoso de un OPCPA de infra-rojo medio. El primero es una fuente compacta de infra-rojo medio basada en un láser de fibra generando pulsos de banda ancha utilizando generación por diferencia de frecuencia (DFG por sus siglas en inglés) en el cristal no lineal CdSiP2. Este láser es la fuente origen del OPCPA y genera pulsos con un ancho de banda compatible con una duración menor a 3 ciclos ópticos a la longitud de onda central de 7 µm. El segundo subsistema es una fuente de bombeo basada en un amplificador de pulso dispersado (CPA por sus siglas en inglés) en el material Ho:YLF bombeado por un láser comercial de fibra dopada con tulio. El sistema de bombeo proporciona más de 0.25 J de energía por pulso a una longitud de onda de 2052 nm. El sistema láser descrito en esta tesis es un paso importante hacia el desarrollo de una fuente de infra-rojo medio capaz de generar pulsos con energía de multi-mJ de pocos ciclos ópticos de duración y fase de portador a envolvente estable (CEP por sus siglas en inglés). El sistema está diseñado para operar a una longitud de onda central de 7 µm, generando pulsos con una energía de 0.2 mJ y una duración temporal de 180 fs a una frecuencia de repetición de 100 Hz. La especificación del láser presentado en este trabajo conduce a una potencia máxima de 1.1 GW y potencialmente a una intensidad máxima de 7 · 1014 W / cm2. Estos valores ya son compatibles con experimentos de campo fuerte y permiten una fuerza pondero-motriz 77 veces mayor que un láser estándar de Titanio-Zafiro.Postprint (published version

Development of a high intensity Mid-Ir OPCPA pumped by a HO:YLF amplifier

The continuous development of laser sources delivering ultra-short light pulses underpins much of the current progress in experimental science, particularly in the domain of physics concerned with strong-field phenomena. Laser systems that allow scaling of strong-field experiments to unexplored regions of the electromagnetic spectrum, specially the mid-IR range (2 µm < lambda < 20 µm), have proved to be a powerful tool enabling the study of new physical processes. It is becoming clear however, that conventional laser sources are unsuited for this purpose, and in order to fully investigate these novel regimes a new generation of laser systems is required. This thesis describes a new laser source of high-intensity, mid-IR light. A long-wavelength pumped optical parametric chirped pulse amplifier (OPCPA) design is chosen as the architecture for this laser, overcoming many of the drawbacks hindering other approaches. This thesis presents two novel sub-systems required for the successful development of a mid-IR OPCPA. The first is a compact, fibre-driven source of broadband mid-IR pulses relying on difference frequency generation (DFG) in the nonlinear crystal CdSiP2. This laser is the seed source in the OPCPA and supports transform-limited pulses corresponding to less than 3 optical cycles at the operating wavelength of 7 µm. The second sub-system is a pump source based on a Ho:YLF chirped pulse amplifier (CPA) pumped by commercial Tm-fibre laser. The pump system delivers over 0.25 J of pulse energy at a wavelength of 2052 nm. The laser system described in this thesis is a developmental milestone towards the realisation of a multi-mJ source of few-cycle duration, carrier-to-envelope phase (CEP) stable mid-IR pulses. The system is designed to operate at a centre wavelength of 7 µm, delivering pulses with an energy of 0.2 mJ and a temporal duration of 180 fs at 100 Hz repetition rate. The output parameters of the laser presented in this work lead to a peak power of 1.1 GW and potentially a peak intensity of 7·1014 W/cm2. These values are already compatible with strong-field experiments and enable a ponderomotive force 77 times larger than a standard Ti:Sapphire laser.El desarrollo de fuentes de luz láser que emiten pulsos ultracortos sustenta una parte importante del progreso actual en ciencia experimental, especialmente en el ramo de la física relacionada con los fenómenos de campo electromagnético intensos. Los sistemas láser que permiten escalar experimentos de campo electromagnético intenso a regiones sin explorar del espectro electromagnético, especialmente en el rango del infra-rojo medio (2 µm < lambda < 20 µm), han demostrado ser una poderosa herramienta facilitando el estudio de nuevos procesos físicos. Sin embargo, las fuentes láser convencionales no son adecuadas para este propósito, y para investigar a fondo estos nuevos regímenes se requiere una nueva generación de sistemas láser. Esta tesis describe una nueva fuente láser de luz de infra-rojo medio de alta intensidad. La arquitectura que elegimos es un amplificador de pulso óptico dispersado paramétrico (OPCPA por sus siglas en inglés) bombeado con una longitud de onda larga y superando así muchos de los inconvenientes de otros diseños. Esta tesis presenta dos sub-sistemas nuevos necesarios para el desarrollo exitoso de un OPCPA de infra-rojo medio. El primero es una fuente compacta de infra-rojo medio basada en un láser de fibra generando pulsos de banda ancha utilizando generación por diferencia de frecuencia (DFG por sus siglas en inglés) en el cristal no lineal CdSiP2. Este láser es la fuente origen del OPCPA y genera pulsos con un ancho de banda compatible con una duración menor a 3 ciclos ópticos a la longitud de onda central de 7 µm. El segundo subsistema es una fuente de bombeo basada en un amplificador de pulso dispersado (CPA por sus siglas en inglés) en el material Ho:YLF bombeado por un láser comercial de fibra dopada con tulio. El sistema de bombeo proporciona más de 0.25 J de energía por pulso a una longitud de onda de 2052 nm. El sistema láser descrito en esta tesis es un paso importante hacia el desarrollo de una fuente de infra-rojo medio capaz de generar pulsos con energía de multi-mJ de pocos ciclos ópticos de duración y fase de portador a envolvente estable (CEP por sus siglas en inglés). El sistema está diseñado para operar a una longitud de onda central de 7 µm, generando pulsos con una energía de 0.2 mJ y una duración temporal de 180 fs a una frecuencia de repetición de 100 Hz. La especificación del láser presentado en este trabajo conduce a una potencia máxima de 1.1 GW y potencialmente a una intensidad máxima de 7 · 1014 W / cm2. Estos valores ya son compatibles con experimentos de campo fuerte y permiten una fuerza pondero-motriz 77 veces mayor que un láser estándar de Titanio-Zafiro

Gas-phase broadband spectroscopy using active sources: progress, status, and applications

Broadband spectroscopy is an invaluable tool for measuring multiple gas-phase species simultaneously. In this work we review basic techniques, implementations, and current applications for broadband spectroscopy. We discuss components of broadband spectroscopy including light sources, absorption cells, and detection methods and then discuss specific combinations of these components in commonly used techniques. We finish this review by discussing potential future advances in techniques and applications of broadband spectroscopy

Laser direct-write of optical components prepared using the sol-gel process

Research in manufacturing techniques for novel and cost effective optical components has focused on versatile new materials and low temperature processing. The laser direct-write of sol-gel optical films has the potential for addressing these two needs for the fabrication of photonic components for rapid prototyping purposes. The combination of Solid Freeform Fabrication (SFF) and Direct-Write (DW) approaches to manufacturing, along with the use of high optical quality materials prepared by the sol-gel process, can result in optical components produced with maskless techniques and with the potential of being used as real products. The fundamental approach in this research consisted in four steps. Initially the sol was synthesized under controlled atmospheric conditions. This was followed by the deposition of the sol-gel thin films by spin coating. After deposition the film was thermally and in some cases chemically treated. The final step involved the use of a laser source for photothermal or photochemical processing of the film, translating the sample through an XY stage. This research provides a detailed study of the preparation procedures of various sol-gel materials (inorganic and hybrid organic/inorganic), with the goal of developing a repeatable and reliable process of high optical quality films. The main experimental aspects explored were the synthesis, deposition, thermal and laser processing of the sol-gel materials. It also presents experimental results that demonstrate light propagation through a simple waveguide made by the proposed process. In addition, this research provides an example of the importance of using design methodology and systems design techniques, as effective strategies for the development of innovative manufacturing processes that involve a great number of parameters. The results of this research set the groundwork for the development of a fully automated direct-write SFF machine that is capable of depositing high optical quality sol-gel films, thermally treating the films, and using a laser to direct-write the structures on inorganic or hybrid organic/inorganic glassy matrices.Mechanical Engineerin

Micro/Nano Devices for Blood Analysis, Volume II

The development of micro- and nanodevices for blood analysis continues to be a growing interdisciplinary subject that demands the careful integration of different research fields. Following the success of the book “Micro/Nano Devices for Blood Analysis”, we invited more authors from the scientific community to participate in and submit their research for a second volume. Researchers from different areas and backgrounds cooperated actively and submitted high-quality research, focusing on the latest advances and challenges in micro- and nanodevices for diagnostics and blood analysis; micro- and nanofluidics; technologies for flow visualization and diagnosis; biochips, organ-on-a-chip and lab-on-a-chip devices; and their applications to research and industry

Novel active sweat pores based liveness detection techniques for fingerprint biometrics

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Liveness detection in automatic fingerprint identification systems (AFIS) is an issue which still prevents its use in many unsupervised security applications. In the last decade, various hardware and software solutions for the detection of liveness from fingerprints have been proposed by academic research groups. However, the proposed methods have not yet been practically implemented with existing AFIS. A large amount of research is needed before commercial AFIS can be implemented. In this research, novel active pore based liveness detection methods were proposed for AFIS. These novel methods are based on the detection of active pores on fingertip ridges, and the measurement of ionic activity in the sweat fluid that appears at the openings of active pores. The literature is critically reviewed in terms of liveness detection issues. Existing fingerprint technology, and hardware and software solutions proposed for liveness detection are also examined. A comparative study has been completed on the commercially and specifically collected fingerprint databases, and it was concluded that images in these datasets do not contained any visible evidence of liveness. They were used to test various algorithms developed for liveness detection; however, to implement proper liveness detection in fingerprint systems a new database with fine details of fingertips is needed. Therefore a new high resolution Brunel Fingerprint Biometric Database (B-FBDB) was captured and collected for this novel liveness detection research. The first proposed novel liveness detection method is a High Pass Correlation Filtering Algorithm (HCFA). This image processing algorithm has been developed in Matlab and tested on B-FBDB dataset images. The results of the HCFA algorithm have proved the idea behind the research, as they successfully demonstrated the clear possibility of liveness detection by active pore detection from high resolution images. The second novel liveness detection method is based on the experimental evidence. This method explains liveness detection by measuring the ionic activities above the sample of ionic sweat fluid. A Micro Needle Electrode (MNE) based setup was used in this experiment to measure the ionic activities. In results, 5.9 pC to 6.5 pC charges were detected with ten NME positions (50μm to 360 μm) above the surface of ionic sweat fluid. These measurements are also a proof of liveness from active fingertip pores, and this technique can be used in the future to implement liveness detection solutions. The interaction of NME and ionic fluid was modelled in COMSOL multiphysics, and the effect of electric field variations on NME was recorded at 5μm -360μm positions above the ionic fluid.This study is funded by the University of Sindh, Jamshoro, Pakistan and the Higher Education Commission of Pakistan

The Boston University Photonics Center annual report 2010-2011

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center in the 2010-2011 academic year. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This report summarizes activities of the Boston University Photonics Center (BUPC) during the period July 2010 through June 2011. These activities span the Center’s complementary missions in education, research, technology development, and commercialization. In education, 21BUPC graduate students received Ph.D. diplomas. BUPC faculty taught 20 photonics courses. One graduate student was funded through the Photonics Center Dean’s Fellowship Program. BUPC supported the Research Experiences for Teachers (RET) in Biophotonic Sensors and Systems. In addition to working in the laboratories and heading to Northeastern University for shared seminars, the eight teachers split into two groups to participate in cleanroom activities. The University hosted its annual Science and Engineering Day, where the Photonics Center sponsored the Herbert J. Berman "Future of Light" Prize. Professor Goldberg’s Boston Urban Fellows Project started its sixth year. For more on our education programs, turn to the Education section on page 62. In research, BUPC faculty published journal papers spanning the field of photonics. Eleven patents were awarded to faculty this year for new innovations in the field. A number of awards for outstanding achievement in education and research were presented to BUPC faculty members. These honors include the NSF CAREER Award for Professors Altug, the 2010 R&sD 100 Award for Professor Bifano, and the Dean’s Catalyst Award for Professor Joshi. New external grant funding for the 2010-2010 fiscal year totaled $20.9M. For more information on our research activities, turn to the Research section on page 24. In technology development, this year was the beginning of a transitional period at the Photonics Center as ARL pipeline programs were completed and new research projects were proposed as part of the newly funded National Science Foundation (NSF) Industrial University Cooperative Research Center (I/UCRC) on Biophotonic Sensors and Systems. As researchers finished programs for ARL development, many successfully presented programs at the first annual I/UCRC meeting in April 2011. In the I/UCRC model, industry members of the Center provide the market vision and orient research to solve urgent market needs – in an extension of the successful ARL pipeline model in which the Department of Defense’s urgent needs motivated our research goals. For more information on our technology development pipeline and projects, turn to the Technology Development section on page 49. In commercialization, the business incubator continues to operate at capacity. Its tenants include ten technology companies with a majority having core business interests primarily in photonics and life sciences. It houses several companies founded by current and former BU faculty and students and provides students with an opportunity to assist, observe, and learn from start-up companies. For more information about business incubator activities, turn to the Business Incubation chapter in the Facilities and Equipment section on page 74. In early 2010, the BUPC unveiled a five-year strategic plan as part of the University’s comprehensive review of centers and institutes. The BUPC strategic plan will enhance the Center’s position as an international leader in photonics research. For more information about the strategic plan, turn to the BUPC Strategic Plan section on page 11