Nanophotonics: Accessibility and Applicability (2008)

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Appendix D Selected Research Groups In Plasmonics introduction Appendix D presents supporting material for Chapter 2, “Nanoscale Phenomena Underpinning Nanophotonics.” Not intended to be exhaustive, this appendix describes a representative sampling of research efforts in 10 areas of plasmonics. In addition, it provides an approximate scale of international research in these specific scientific areas. Reference is made to Appendix D within subsections of the major sections entitled “Plasmonics,” “Emerging Topics of Phonon Polaritons,” and “Terahertz Wave- guides” in Chapter 2. Presented in the same order as their corresponding subsections in Chapter 2, following are the 10 areas of plasmonics research addressed below: • Localized Surface Plasmon Resonance Sensing, • Surface-Enhanced Spectroscopy, • Techniques for Imaging and Spectroscopy of Plasmonic Structures, • Extraordinary Transmission, Subwavelength Holes, • Plasmonic Waveguides and Other Electromagnetic Transport Geometries, • Plasmon-Based Active Devices, • Plasmon-Enhanced Devices, • Plasmonics in Biotechnology and Biomedicine, • Phonon Polaritons, and • Emerging Topics in Plasmonics. The research groups within each area listed above are alphabetized by the last name of the group’s leader. 203 

204 Nanophotonics Localized Surface Plasmon Resonance Sensing: Selected Research Groups • Jason H. Hafner, Rice University, Houston, Texas—Gold nanostars are asymmetric nanoparticles that show polarization-dependent scattering spectrum. This has been demonstrated to show large surface plasmon resonance (SPR) shifts in single-particle scattering measurements.�������������� ������������� Dr. Hafner’s group is currently pursuing single-particle, single-binding-event sensing using nanostars (Nehl et al., 2004). • Naomi J. Halas, Rice University, Houston, Texas—Dr. Halas’s group has developed a variety of nanoparticles that exhibit large SPR sensitivities. These include silica core gold nanoshells and “nanorice” particles (Tam et al., 2004; Wang and Mittleman, 2006). • Mikael Käll, Chalmers University of Technology, Göteborg, Sweden�LSPR sensing of single — holes in gold films and the ensemble measurements have been used to demonstrate the LSPR sensitivity by functionalizing with alkanethiols of different lengths. Other geometries made by electron-beam lithography have also been developed. The group at Chalmers University has also developed techniques to study surface modifications in the lipid layer and other chemical changes that occur at the hole sites on lipid layers supported on gold films with nanometer-size holes (Rindzevicius et al., 2005). • Nicholas Kotov, University of Michigan, Ann Arbor�Dr. Kotov developed a layer-by-layer assem- — bly technique to fabricate thin films of mixed anisotropic nanoparticles and controlled surface plasmon absorption. • J.R. Sambles, University of Exeter, Exeter, United Kingdom�Dr. Sambles’s group has developed — an acoustooptical tunable filter to enhance the SPR sensitivity of gold films used to detect NO gas close to the surface, the binding of biological molecules in solution, and the electrochemical modifications in the films as different molecules attach to the surface (Jory et al., 1995). • Jennifer Shumaker-Parry, University of Utah, Salt Lake City, Utah�Dr. Shumaker-Parry’s group — has developed SPR microscopy as a technique for array-based molecular recognition studies. SPR microscopy using an asymmetric particles array (crescent-shaped particles) provides a label-free method for high-throughput, quantitative, real-time kinetic studies of biomolecule interactions (e.g., protein-DNA, protein-protein, protein-vesicle) (Shumaker-Parry et al., 2005). • Richard P. Van Duyne, Northwestern University, Evanston, Illinois—Dr. Van Duyne’s group has used nanosphere lithography silver triangles as localized surface plasmon resonance (LSPR) sensors to study chemical binding and unbinding events. Both ensemble measurements of silver triangle arrays and single-particle measurements have been used to study LSPR shifts that are due to molecules binding to the surface (Malinsky et al., 2001; McFarland and Van Duyne, 2003). This group has also used LSPR sensing to detect biomarkers for Alzheimer’s disease. • Younan Xia, University of Washington, Seattle, Washington—D����������������������������� r. Xia’s group has developed hollow gold nanoshells, and nanocube particles that show high LSPR sensitivity. Ensemble ��������� measurements on the nanoshells and single-particle measurements on the nanocubes have been performed (Sherry et al., 2005; Sun and Xia, 2002). Surface-Enhanced Spectroscopy: Selected Research Groups • Louis Brus, Columbia University, New York, New York—Dr. Brus’s group is involved in studies ������������������������������������ relating to the origin of large enhancement factors in SERS from silver colloid particles (Michaels et al., 2000). The group is also investigating the chemical effect in the SERS enhancement. 

APPENDIX D 205 • Peter Griffiths, University of Idaho, Moscow—Dr. Griffith’s group has developed techniques to use surface-enhanced infrared absorption spectroscopy (SEIRA) to increase the sensitivity at which the molecules eluting from a gas chromatograph (GC) can be identified. This instrument has better sensitivity than a traditional GC/mass spectrometer (Bjerke et al., 1999). The group has also developed instrumentation to study SEIRA of the atmosphere to identify pollutants in the environment and gases formed in compost piles on dairy farms. • Naomi J. Halas, Rice University, Houston, Texas—Dr. Halas’s group has developed gold and silver nanoshell-based substrates for SES and explored many of the basic physics origins of SERS and SEF (Tam et al., 2007). The group has also developed a nanoscale pH sensor based on SERS of molecules adsorbed on nanoshells (Bishnoi et al., 2006). • Mikael Käll, Chalmers University of Technology, Göteborg, Sweden—Dr. Käll’s group has been involved with surface-enhanced Raman and surface enhanced fluorescence (SEF) on nanoparticle substrates as well as nanometer-sized holes in metallic films. The group has developed both experi- mental techniques for exploring plasmons in various nanostructures and theoretical background for SERS and SEF (Xu et al., 2004). • Satoshi Kawata, ����������������� Osaka and Riken, Tokyo, Japan—Dr. Kawata’s research group Osaka University, looks at various enhanced nonlinear spectroscopic techniques using a metallized tip to enhance the signal of the same, and to minimize the volume of the sample that is probed. The group has developed techniques for tip-enhanced Raman spectroscopy and tip-enhanced coherent Raman spectroscopy, a nonlinear Raman scattering technique that utilizes two lasers to overpopulate the excited state of the system. These techniques are then used to image biological molecules, such ������������������������������������������������������������������� as adenine, and other biological systems (Ichimura et al., 2004). • Katrin Kneipp, Wellman Center for Photomedicine, Harvard University, Medical School, Massa- chusetts Institute of Technology—Dr. Kneipp is one of the pioneers of single-molecule detection ����������������������������������������������������������� using SERS (Kneipp et al., 1997). Currently she is investigating SERS and surface-enhanced Raman optical activity in vivo for molecular and chemical probing of cell and biological structures and biomedically relevant molecules (Kneipp et al., 2006a). • Joseph R. Lakowicz and Chris D. Geddes, University of Maryland, Baltimore—Dr. Lakowicz is the director for the Center for Fluorescence Spectroscopy. He has been involved with numerous techniques in advanced fluorescence spectroscopy, including surface-enhanced fluorescence, surface-enhanced multiphoton fluorescence spectroscopy, and so on. He is also the author of a number of review articles and books on fluorescence spectroscopy, including Principles of Fluo- rescence Spectroscopy. • Martin Moskovits, University of California at Santa Barbara—Dr. Moskovits has been involved in surface-enhanced Raman spectroscopy and the development of different nanostructures for SES (Moskovits, 1985). • Lukas Novotny, University of Rochester, Institute of Optics, Rochester, New York—This group has been involved in the development of tip-enhanced Raman spectroscopy as an imaging technique. Dr. Novotny’s group developed a tip-enhanced Raman scattering microscope for the chemically specific imaging of surfaces. This technique is being applied for the study of carbon nanotubes, stress analysis in semiconductors, and membrane proteins. Currently the group is also utilizing this for tip-enhanced fluorescence spectroscopy. The group has demonstrated single-molecule fluorescence and the distance-dependent fluorescence profile as a gold or silver tip is moved closer to a fluorescent dye molecule on a surface (Anger et al., 2006). The Novotny group is also involved in surface-enhanced sum frequency generation using clusters of gold nanoparticles as substrates (Danckwerts and Novotny, 2007). 

206 Nanophotonics • Masatoshi Osawa, Hokkaido University, Sapporo, Japan�Dr. Osawa is one of the pioneers of — SEIRA. His group studies SERS and SEIRA in ATR geometry of chemical reactions and confir- mation of proteins in solution electrochemically. He is the author of a number of review articles on SERS and SEIRA (Osawa, 2001). • Bruno Pettinger, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany—This group’s research is on the mechanism of SERS on gold and platinum surfaces. In addition, the group has developed techniques for TERS in the junctions formed between silver and gold scan- ning tunneling microscope tips with dye molecules adsorbed on smooth metal surfaces (Pettinger, 2006b, 2006a). • Annemarie Pucci, University of Heidelberg, Germany—Dr. Pucci’s group has been involved in SEIRA using different nanoparticle geometries for a long time (Enders and Pucci, 2006). • Vahid Sandoghdar, ETH, Zurich, Switzerland—Dr. Sandoghdar’s group has combined far-field ������������������������������������������ fluorescence microscopy with scanning probe machinery to localize single molecules in a sample to a very small fraction of the wavelength of light. Using a single colloid attached to a scanning near-field optical microscopy tip, the group has studied single-molecule fluorescence.���������� (Kuhn et al., 2006)�. • Vladimir M. Shalaev, Purdue University, West Lafayette, Indiana—Dr. Shalaev developed semi- continuous silver films as SERS substrates (Genov et al., 2004). Currently developing a SERS- based sensor to examine differences in Raman spectra of two insulin isomers, human insulin and its analog insulin lispro, which differ only in the interchange of two neighboring amino acids (Drachev et al., 2004). • Richard P. Van Duyne, Northwestern University, Evanston, Illinois—Dr. Van Duyne is one of the pioneers in the field of SERS. From studying the basic physics behind SERS, and development of optimal SERS substrates, Dr. Van Duyne’s group is now actively involved in applications of SERS for biomedical sensing. These range from in vivo optical glucose sensors to the sensing of bioterrorism agents. • Renato Zenobi, ETH Swiss Federal Institute, Zürich, Switzerland—The Zenobi group is ��������� actively involved in the fabrication and design of various TERS probes based on atomic force microscopy (AFM) tips��������������������������������������������������������������������������������� . This group combines a ��������������������������������������������������������� laser scanning confocal microscope and an AFM capable of both tip and sample scan modes. This capability provides highly localized enhancements when the tip is present and offers more uniform enhancement when scanning over the sample (Vannier et al., 2006). Techniques for Imaging and Spectroscopy of Plasmonic Structures: Selected Research Groups • Franz R. Aussenegg, Joachim R. Krenn, and Alfred Leitner, Karl-Franzens-University, Graz, Austria—This group has extensively applied photon scanning tunneling microscopy (PSTM) and leakage-radiation microscopy to study the propagation of surface plasmons in metallic strip and particle array waveguides, and has applied passive devices such as Bragg reflectors, beam splitters, and plasmon corrals. In addition, this group has applied other techniques such as surface-enhanced Raman scattering to image the fields around plasmonic devices and dark-field microspectroscopy to study the resonant modes of nanowire waveguides. • Sergey I. Bozhevolnyi, University of Aalborg, Aalborg, Denmark—This group has applied collec- tion mode near-field scanning optical microscopy (NSOM) to studying the propagation of surface 

APPENDIX D 207 plasmons in particle-based and channel-based waveguides, including measuring the performance of passive devices such as Mach-Zehnder interferometers and waveguide-ring resonators. • Mark Brongersma, Stanford University, Stanford, California—The Brongersma group is an engineering group focusing on the development of methods to guide and manipulate light using plasmonic nanostructures. To this end, the group extensively employs photon tunneling scan- ning microscopy utilizing microfabricated NSOM probes to measure the properties of plasmonic devices. • Jochen Feldmann and Thomas Klar, Ludwig-Maximilians-Universität München, Munich, ­ ermany—This group has pioneered the use of dark-field microspectroscopy to study the scatter- G ing properties of individual metallic nanoparticles and the application of this technique to single- particle surface plasmon resonance sensing of biomolecules. In addition, this group has studied enhanced photoluminescence from gold nanoparticles utilizing excitation with an ultrafast laser. • Reinhard Guckenberger, Fritz Keilmann, and Rainer Hillenbrand, Max-Planck-Institut für ­Biochemie Abteilung Molekulare Strukturbiologie, Martinsried, Germany—This group has worked extensively on extending ANSOM into the infrared spectral region. In addition to looking at surface plasmon polartions in particles, the group has studied the closely related phenomenon of surface phonon polaritons on SiC in the infrared (IR). Recently the group developed a technique based on pseudo­ heterodyne detection to eliminate the background in ANSOM images, which, unlike previous techniques, is suitable for use over broad wavelength ranges spanning the near-ultraviolet to far-IR spectral ranges (Ocelic et al., 2006). This group has been working on techniques for ANSOM in the IR and is studying surface photon polaritions on SiC in addition to surface plasmon polaritons. • Victor I. Klimov, Los Alamos National Laboratory, Los Alamos, New Mexico—While primarily focused on quantum dots, Dr. Klimov’s group has made important contiburtions to the study of plasmons in metallic nanoparticles by pioneering the use of femtosecond white-light continuum radiation for linear spectroscopy of single gold nanoparticles with an illumination-mode NSOM (Mikhailovsky et al., 2004). • Brahim Lounis, Centre de Physique Moleculaire Optique et Hertzienner, Centre National de la Recherche Scientifique (CNRS)—Université Bordeaux 1, Cedex, France—Dr. ������������������� Lounis’s group has led the development of photothermal heterodyne to measure the absorption spectrum of small gold colloid plasmons. This group is focused on applying this technique to develop contrast agents for microscopy of the dynamics in biologically relevant systems. • Alfred Meixner, Eberhard-Karls-Universität Tübingen, Tübingen, Germany—Dr. Meixner’s group ���������������� has developed a method for determining the orientation of nonsymmetric nanoparticles on a sur- face using far-field confocal microscopy with higher-order Guassian beams (doughnut mode). This is of importance, as previously either electron microscopy or topographic imaging with an AFM or NSOM tip was required to determine unambiguously the orientation of particles significantly smaller than the diffraction limit. • Hrvoje Petek, University of Pittsburgh, Pittsburgh, Pennsylvania—Dr. Petek’s group has been studying the dynamics of materials using a frequency-doubled 10 femtosecond Ti:sapphire laser and two-photon time-resolved photoelectron emission spectroscopy and imaging. The group recently applied this technique to two-photon photoelectron emission imaging of surface plasmon polariton propagation, obtaining the currently highest simultaneous temporal and spatial image of surface plasmon polariton wave-packet propagation. • Albert Polman, FOM [Fundamental Research on Matter] Institute for Atomic and ­ Molecular Physics (AMOLF), Amsterdam, The Netherlands—This group has developed techniques for measuring the propagation of surface plasmon polaritons (SPPs) on metal film structures by 

208 Nanophotonics c ­ athodoluminescence (van Wijngaarden et al., 2006). This group has also investigated the propa- gation of purely bound infrared SPP modes on metal strips on the glass/silver interface at tele­ communications wavelengths by looking at photoluminescence of Er+ deposited in the glass substrate of the waveguides and excited by the near field extending from the waveguide (Verhagen et al., 2006). Leakage radiation microscopy and PSTM are not able to image such modes propa- gating at the substrate-metal interface, because in the former case the phase-matching condition is not satisfied for the propagation of light in the glass, thereby forbidding the radiation into the glass (unlike waveguides using the metal-air interface), and in the latter case simply because the field is not physically accessible. This group has collaborated extensively with the Atwater group at the California Institute of Technology for their work in surface plasmons (see “Harry A. Atwater” in the section below on “Plasmonic Waveguides and Other Electromagnetic Transport G ­ eometries”). • Fabrice Vallée and Natalia Del Fatti, CNRS and Université Bordeaux 1, Talence, France—This group has developed the technique of spatial modulation spectroscopy using supercontinuum to measure directly the absorption of single gold and silver nanoparticles. This technique has been demonstrated to accurately determine the particle ellipticity by measuring the spectrum with dif- ferent incident polarizations and comparing the results to Mie theory (Muskens et al., 2006). Extraordinary Transmission, Subwavelength Holes: Selected Research Groups • William L. Barnes, University of Exeter, Exeter, Devon, United Kingdom—Dr. Barnes’s group has extended the study of extraordinary transmission beyond subwavelength holes. This group has continued to study the basic processes underlying extraordinary transmission. His group has also studied how surface plasmons mediate light transmission through metal films that contain no subwavelength holes (Andrew and Barnes, 2004). • Steven Brueck, University of New Mexico, Albuquerque—This group has pioneered both the fab- rication and characterization of annular (coaxial) arrays and the use of these arrays for nonlinear optics applications (by etching the structures into a gallium arsenide matrix before depositing the metal films). • Thomas W. Ebbesen, ISIS [Institut de Science d’Ingenierie Supramoleculaires], Université Louis Pasteur, Strasbourg, France—Dr. Ebbesen’s group originally discovered the extraordinary trans- mission phenomenon. The group continues to study and characterize the fundamentals of the phenomenon as well as explore applications. Recently, Dr. Ebbesen’s group has worked on using subwavelength hole arrays coupled with molecules to approach the realization of fast all-optical switching components (Dintinger et al., 2006). • F.J. García-Vidal, Universidad Autónoma de Madrid, Madrid, Spain; Luis Martín-Moreno, ICMA‑CSIC [Instituto de Ciencia de Materiales de Aragon, Consejo Superior de ­Investigaciones Cientificas], Universidad de Zaragoza, Zaragoza, Spain—This group focuses on theoretical s ­ tudies of the extraordinary transmission phenomenon. The group has published many studies that support the surface plasmon view of extraordinary transmission. Recently they have con­tinued to study the phenomenon as well as different geometries for extraordinary transmission. For example, they have recently studied the transmission of light through a rectangular hole (García- Vidal et al., 2006). • Henri J. Lezec, Thomas J. Watson Laboratories of Applied Physics, California, Institute of Tech- nology, Pasadena, and Centre National de la Recherche Scientifique, Paris, France—Dr. Lezec is 

APPENDIX D 209 a proponent and co-originator of the controversial composite diffracted evanescent wave (CDEW) model for explaining the mechanism underlying the extraordinary transmission phenomenon. He has performed experimental measurements supporting this model. • Teri Odom, Northwestern University, Evanston, Illinois—Dr. Odom’s group has done experi- ments that support the surface plasmon model as the major process underlying extraordinary transmission. Conventional studies of extraordinary transmission rely solely on far-field optical data, but by definition, surface plasmons are confined to a surface and therefore cannot be directly detected using far-field measurements. However, using a near-field scanning optical microscope, the large electric field in close proximity to a surface due to surface plasmons can be directly detected, allowing the plasmon oscillations to be imaged. By combining far-field and near-field optical measurements, this group has shown direct evidence for the surface plasmon model of extraordinary transmission (Gao et al., 2006). • Evgeny Popov and Michel Nevière, Institut Fresnel, Domaine Universitaire de Saint Jérôme, Université d’Aix Marseille III, Marseille, France—This group studies the theory underlying the extraordinary transmission phenomenon. It studies the basics of plasmons on films in the presence of different types of nanoapertures. • Tineke Thio, Arinna, LLC, Princeton, New Jersey—Dr. Thio is a proponent and co-originator of the controversial CDEW model for explaining the mechanism underlying the extraordinary transmission phenomenon. She now has her own science consulting firm, Arinna, LLC, were she continues to research the CDEW model and its implications. Plasmonic Waveguides and Other ELECTROMAGNETIC Transport GeometriEs: Selected Research Groups • Harry A. Atwater, Thomas J. Watson Laboratory of Applied Physics, California Institute of Tech- nology, Pasadena—This group has explored using nanoparticle chains as plasmonic waveguides. Nanoparticles’ plasmon resonances couple to each other via the optical near field, allowing highly localized waveguides that can support sharp bends quite well. Recently the group’s efforts have shifted toward metal-insulator-metal structures for plasmon waveguiding. The group has experi- mentally achieved this structure and characterized its confinement and propagation character- istics, as discussed above (see “Albert Polman” in the section on “Techniques for Imaging and S ­ pectroscopy of Plasmonic Structures”). • Pierre Berini, School of Information Technology and Engineering, University of Ottawa, ­Canada— Dr. Berini’s group was the first to observe long-range propagation in metallic stripe waveguides. The group found plasmons that propagated out to several millimeters distance. The group has extensively studied this system both experimentally and theoretically. Recently, Dr. Berini defined figures of merit for plasmonic waveguides that seek to quantify the trade-off between losses that shorten propagation lengths and confinement of the plasmon mode to subwavelength sizes (Berini and Lu, 2006). • Sergey I. Bozhevolnyi, Aalborg University, Aalborg, Denmark—Dr. Bozhevolnyi’s group was the first to realize the channel plasmon polariton experimentally. After demonstrating that such struc- tures can be fabricated and working to optimize the parameters of the groove-shaped waveguides, the group demonstrated that such structures could support both long distance propagation and high spatial confinement of the electromagnetic modes. This group has demonstrated the ability to make basic optical components from these waveguides such as Mach-Zendher interferometers, 

210 Nanophotonics Y-splitters, and resonant ring structures. Dr. Bozhevolnyi continues to study these waveguiding structures. • Mark Brongersma, Geballe Laboratory for Advanced Materials, Stanford University, ­California— Mark Brongersma’s group has extensively studied surface plasmon polariton propagation on metallic stripe waveguides. The group has demonstrated both experimentally and theoretically that while these types of waveguides are capable of long-range propagation of SPPs, they are not able to confine such guided modes in a subwavelength geometry. The group has shown the difference between true, guided modes and leaky modes of the metallic stripe, and has predicted and experimentally verified that at certain stripe widths, bound modes are cut off and no longer propagate. • Alain Dereux and Jean-Claude Weeber, Laboratoire de Physique de l’Université de Bourgogne, Optique Submicronique, Dijon, France—This group has studied many of the plasmonic wave­ guiding structures discussed above. It has focused mostly on characterizing metallic stripe wave- guides. Recently the group has studied right-angle bends in such waveguides and has managed to successfully route plasmon modes around such bends using tilted Bragg mirrors (Weeber et al., 2005). This group has also studied how metallic nanoparticle chains affect the modes propagating in microscale dielectric waveguides (Quidant et al., 2004). • Dimitri K. Gramotnev, Queensland University of Technology, Brisbane, Australia;D.F.P. Pile, The University of Tokushima, Japan—Gramotnev and Pile have focused most of their attention on channel plasmon waveguides, although they have studied many waveguiding systems. Using finite difference time domain simulations, they conducted many of the first numerical simulation studies of this geometry and originally predicted many of its remarkable waveguiding properties, such as nearly zero loss at sharp bends and high spatial confinement of plasmon modes. • Joachim R. Krenn, Alfred Leitner, and Franz R. Aussennegg, Institut fur Experimentalphysik, Universitat Graz, Austria—This group has studied many geometries for plasmonic wave­guiding, including nanoparticle chains and metallic stripes and nanowires. The group was involved in many of the earliest studies in these areas and, recently has studied a new system for plasmon waveguiding that uses dielectric stripes on a gold substrate (Steinberger et al., 2006). The group found this type of waveguide to be able to propagate guided plasmons efficiently, as well as to direct plasmon modes around gradual bends in an analogous process to total internal reflection and through junctions without significant losses. • Stefan Maier, University of Bath, Bath, United Kingdom—Stefan Maier, originally a graduate student in Harry Atwater’s group, conducted many of the early studies using nanoparticle chains as plasmon waveguides. He has since studied other types of waveguides, and recently, terahertz waveguiding structures. He has suggested using structures with periodic grooves in order to support highly confined SPP-like modes that are ideal for waveguiding in the terahertz spectra range. Plasmon-Based Active Devices: Selected Research Groups • Franz R. Aussenegg, Joachim R. Krenn, and Alfred Leitner, Karl-Franzens-University, Graz, ­ ustria—In addition to its pioneering work in passive plasmonic devices, this group has developed A a monolithically integrated organic diode surface plasmon polariton sensor allowing the direct detection of surface plasmons at the end of a plasmon waveguide. • Sergey I. Bozhevolnyi, University of Aalborg, Aalborg, Denmark—This group is focused on devel- oping plasmonic devices for subwavelength control of optical signals. Toward this end, the group 

APPENDIX D 211 has developed an in-line plasmon modulator based on long-range surface plasmon polaritons propagating on metallic strips embedded in a polymer (Nikolajsen et al., 2004) and a number of passive devices based on strip, particle, and channel waveguides. The group has also studied near-field imaging techniques, including modeling in order to understand the collection properties of uncoated dielectric fiber probes for probing the near field of plasmonic waveguides. • Yang-Fang Chen, National Taiwan University, Taipei, Taiwan, Republic of China—This group’s primary focus is on semiconductor structures such as quantum dots and quantum wells, porous silicon devices, and the magnetic properties of semiconductor systems. Dr. Chen’s group has demonstrated the use of electrically actuated liquid crystals to modulate the spectral position of the plasmon resonance of gold nanorods (Chu et al., 2006). • Raffaele Colombelli, Université Paris Sud, Orsay, France—This group’s focus is on the mid-­infrared (IR), specifically the development of quantum cascade lasers and mid-IR surface ­plasmonics. One aspect of the research is that of combining the two fields to develop devices to directly create surface plasmons using electrical excitation by coupling surface plasmons to quantum well gain media. The group is simultaneously developing this technique for both the construction of active plasmonic devices in the mid-IR and the improvement of the far-field ­ efficiency of quantum cascade lasers. • Christopher C. Davis and Igor I. Smolyaninov, University of Maryland, College Park—The M ­ aryland optics group works in a wide array of fields, from biodetection using tapered optical fibers to active plasmonic devices. In the latter area, the group has demonstrated all-optical devices for controlling the transmission of light using surface plasmons on metal hole arrays (Smolyaninov et al., 2002). • Lukas Eng, Dresden University of Technology, Dresden, Germany—This group works on a range of fields involving nanophotonics, including imaging using NSOM techniques to study ferroelectric thin films, microfabricated NSOM tip fabrication, and active plasmonic devices. Of particular note with respect to active plasmonics is the demonstration of stimulated emission of surface plasmon amplification using an optically pumped dye gain medium on the surface of a silver film (Seidel et al., 2005). • Jochen Feldmann and Thomas Klar, Ludwig-Maximilians-Universität Munich, Germany—This group has demonstrated that the plasmon resonance of spherical gold nanoparticles can be shifted significantly by applying an electrical bias across a cell containing nanoparticles and liquid crystals. In the presence of liquid crystals, the spherical particles become effectively spheroidal optically owing to the controllable anisotropy of the dielectric environment created by the liquid crystals. • Jaime Gómez Rivas, FOM [Fundamental Research on Matter] Institute for Atomic and ­Molecular Physics (AMOLF), Philips Research Laboratories, Eindhoven, The Netherlands—Dr. Rivas’s group is actively involved in developing methods to actively control low-frequency (THz) p ­ lasmons propagating on semiconductor surfaces. In particular, the group recently demonstrated a technique for all-optical switching of terahertz plasmons (Gomez-Rivas et al., 2006). Other research in the group focuses on the optical properties of semiconductor nanowires. • Mikhail A. Noginov, Norfolk State University, Norfolk, Virginia—This group has worked in the areas of random lasers and composite laser media with nonlinear media. It has looked at enhance- ment of surface plasmons by coupling to a dye for gain in conjunction with Vladimir M. Shalaev’s group at Purdue University in West Lafayette, Indiana (Noginov et al., 2006) (see “Vladimir M. Shalaev” in the section above on “Surface-Enhanced Spectroscopy”). 

212 Nanophotonics • Nikolay Zheludev, University of Southampton, Southampton, United Kingdom—In the field of plasmonics, this group has studied active plasmonic switching, nonlinear plasmonic devices, the generation of plasmons by direct excitation with electron beams, and the effects of chirality and broken symmetry in nanophotonic devices. For active plasmonics, this group has developed a technique for the modulation of plasmons by using optical or thermal modification of the phase of gallium, which radically alters the dielectric function changing the propagation of plasmons on the gallium film (Krasavin et al., 2005). In thin films, this effect can be quite fast, on the order of several picoseconds, enabling the high-speed modulation of surface plasmons either optically or potentially electrically. This mechanism is distinctly different from other approaches, as it relies on modifying the waveguide itself rather than the surrounding medium. Plasmon-Enhanced Devices: Selected Research Groups • Harry A. Atwater, California Institute of Technology, Pasadena—This group has wide-­ranging interest in developing materials for nanophotonics including active devices based on semi­conductor nanocrystals and plasmonics. In conjunction with Albert Polman’s group in the Netherlands, this group has characterized the use of plasmons to enhance the radiative decay rate of silicon nanocrystals (Biteen et al., 2006) (see “Albert Polman” in the section above on “Techniques for Imaging and Spectroscopy of Plasmonic Surfaces”). • Toshio Baba, Fundamental and Environmental Research Laboratories, NEC Corporation, Ibaraki, Japan; Kikuo Makita, System Devices Research Laboratories, NEC Corporation, Shiga, Japan— These groups have demonstrated the use of plasmonics to concentrate light into high-speed silicon nanophotodiodes (Ishi et al., 2005). NEC Corporation is also investigating the use of plasmons on concentric ring structures to focus light emitted from diode lasers into nanoscale volumes for optical storage applications. • Federico Capasso, Harvard University, Cambridge, Massachusetts—In the region of plasmon- enhanced devices, this group has been active in developing both plasmon-enhanced quantum cascade lasers (QCLs), and plasmonic nano-antennas. The group has developed in a nano-antenna deposited on the surface of a laser diode for generating intense subwavelength points of light (Cubukcu et al., 2006). It has also demonstrated a single-mode surface-emitting terahertz QCL using double-metal waveguide structures with periodic gratings in the top surface and efficient absorbers to terminate the waveguide to achieve low-divergence vertical output (Tredicucci et al., 2000). • Shanhui Fan and Mark L. Brongersma, Stanford University, Stanford, California—The Fan group studies computational modeling of photonic crystals, micro- and nanophotonic structures, and solid-state devices. The Brongersma group experimentally studies plasmonic devices, plasmon- enhanced lithography, semiconductor nanophotonics, and microresonators. In collaboration, these groups have recently demonstrated theoretically the possibility of using surface plasmons to enhance mid-IR detectors using surface plasmons on metallic nanowire gratings. • Martin Green, University of New South Wales, Sydney, Australia—Dr. Green is the director of the ARC Photovoltaics Centre of Excellence and therefore focuses on energy applications—specifi- cally, on ways of developing highly efficient photovoltaic devices as well as on work to improve the emission efficiency of light-emission structures. To this end, he has made important contribu- tions by demonstrating the enhancement both in emission and absorption by a thin-film silicon diode device operating near the band edge (Pillai et al., 2006). 

APPENDIX D 213 • David A.B. Miller, Stanford University, Stanford, California—The Miller group is focused on developing optoelectronic materials, devices, and systems. This includes work on topics such as ultrafast all-optical switches, optical interconnects, and high-speed optical A/D converters. Of particular note is the development of C-apertures in metallic films to create plasmon-enhanced photodiodes at telecommunications wavelengths (Tang et al., 2006). • Axel Scherer, California Institute of Technology, Pasadena—This group has investigated the coupling of surface plasmons to blue light emitters in order to enhance the output for use in high- efficiency illumination devices. Enhanced emission from indium gallium nitride quantum well structures and organic polymers using surface plasmons by radiative rate enhancement has been demonstrated in collaboration with Yukio Narukawa and Takashi Mukai of the Nichia Corpora- tion in Tokushima, Japan (Okamoto et al., 2004). A similar mechanism has been demonstrated to work for enhancing the output of conjugate polymers which show potential for use as organic light-emitting diodes (Neal et al., 2006). While thus far this research has been with optically excited systems, the radiative rate enhancements should persist irrespective of pumping method and therefore would be applicable in electrically stimulated devices as well. • Alessandro Tredicucci and Fabio Beltram, NEST [National Enterprise for nanoScience and nanoTechnology] CNR-INFM [Consiglio Nazionale delle Recherche Insitutuo Nazionale per la Fisica della Materia] and Scuola Normale Superiore, Pisa, Italy—This group is focused on the development of novel quantum cascade lasers using intersubband transitions in semiconductor superlattices to generate light in the terahertz spectral region. Toward this end, the group has employed surface plasmons to enhance the overall performance of QCLs and to control the mode structure to produce vertical-emitting single-mode lasers (Tredicucci et al., 2000). Plasmonics in Biotechnology and Biomedicine: Selected Research Groups • Naomi J. Halas, Jennifer West, and Rebekah Drezek, Rice University, Houston, Texas—The Halas group has exploited the plasmonic heating of gold nanoshells in a variety of biomedical applications. Nanoshells have been used to enhance the absorption of near infrared in laser tissue welding (Gobin et al., 2005) and in photothermal ablation of cancer cells (O’Neal et al., 2004; Hirsch et al., 2003). This work has led to a comprehensive scheme for the optical imaging of cancer cells using gold nanoshells and photothermal ablation (Loo et al., 2005). A nanoshell-based rapid immunoassay in whole blood has been developed that exploits the LSPR shift as nanoshells aggregate in the presence of a specific antibody (Hirsch et al., 2003). • Katrin Kneipp, Wellman Center for Photomedicine, Harvard University, Medical School, Massa- chusetts Institute of Technology—Dr. Kneipp is one of the pioneers of single-molecule detection ����������������������������������������������������������� using SERS (Kneipp et al., 1999). Currently she is investigating cellular uptake of gold colloid and utilizing the gold colloid aggregates formed in the cells to probe the chemical composition of biological structures, inside cells at the single-molecule level and at the nanoscale (Kneipp et al., 2006b). • Catherine J. Murphy, University of South Carolina, Columbia—Dr. Murphy’s group has developed ����������������������������� a novel optical technique that combines the light elastically scattered from gold nanorods with digital image analysis to track local deformations that occur in vitro between cells, in real time, under dark-field optical microscopy (Stone et al., 2007). • Richard P. Van Duyne, Northwestern University, Evanston, Illinois—Dr. Van Duyne’s group has successfully implemented localized surface plasmon resonance sensing to detect ���������������� physiologically 

214 Nanophotonics relevant concentrations of a marker for Alzheimer’s disease. The group has developed an optical biosensor using LSPR to monitor the interaction between the antigen, amyloid derived diffus- ible ligands (ADDLs), and specific anti-ADDL antibodies. Using the sandwich assay format, this nanosensor provides quantitative binding information for both antigen and second antibody detection that permits the determination of ADDL concentration and offers the unique analysis of the aggregation mechanisms of this Alzheimer’s disease pathogen at physiologically relevant m ­ onomer concentrations (Haes et al., 2005). The group has also developed various surfaced- enhanced Raman spectroscopy (SERS) substrates for in vivo glucose sensing. In vivo glucose sensors are based on SERS using alkanethiol modified silver films on nanosphere substrates. The alkanethiol self-assembled monolayers (SAMs) allow the glucose to partition into the SAMs layer and can be detected using SERS (Lyandres et al., 2005; Stuart et al., 2006b). The Van Duyne group has also developed optical biosensors for the detection of anthrax biomarkers (Zhang et al., 2005; Zhang et al., 2006) and chemical warfare agent half-mustard agent (Stuart et al., 2006a). • Nikolay I. Zheludev, Southampton University, Southampton, United Kingdom—Dr. Zheludev developed a���������������������������������������������������������������������������������� new, noncontact high-capacity optical tagging technique based on the use of nano­ structured barcodes. The tags are generated from a number of superimposed diffraction gratings. The capacity for up to 68,000 distinguishable tags has been demonstrated. These tags can be used to tag deoxyribonucleic acid (DNA) sequences for high-throughput genome sequencing (Galitonov et al., 2006). Phonon Polaritons: Selected Research Groups • Rainer Hillenbrand, Nano-Photonics Group, Max-Planck-Institute für Biochemie and Center for Nanoscience, Martinsried, Germany—This group first observed near-field coupling of phonon polaritons to a subwavelength tip and characterized this phenomenon. The group suggested that this technique could allow for applications in the mid-infrared that are analgous to plasmon-based phenomena in the visible and near-infrared ranges. The group is currently exploring the use of the s-SNOM technique to study applications of surface phonon polaritons. • Gennady Shvets, Department of Physics and Institute for Fusion Studies, University of Texas at Austin�This group has proposed the use of surface phonon polaritons on a silicon carbide surface — to realize desktop particle accelerator technology. The group has designed a device based on this concept and has performed initial tests using numerical modeling techniques as well as experi- mental tests to observe and characterize the phonon modes propagating along the SiC surface. This group continues to develop this technology and progress toward a final product. Emerging Topics in Plasmonics: Selected Research Groups • Dan Grischkowsky, School of Electrical and Computer Engineering, Oklahoma State University, Stillwater—This group has studied the surface propagation of plasmons on the cylindrical metallic wire system. It has also recently studied the propagation of surface plasmon polaritons on planar metal sheets (Jeon and Grischkowsky, 2006). Like the Sommerfeld waves of the cylindrical wire case, the group has identified these waves on a planar sheet as the classical Zenneck waves. • Stefan Maier, University of Bath, United Kingdom—Dr. Maier originally focused his attention on plasmonic waveguides in the visible and near-infrared spectral range, but he has recently become involved with terahertz plasmonic waveguides as well. He has suggested that metal structures 

APPENDIX D 215 with periodic grooves should support SPP-like waves on their surface that are highly confined to subwavelength sizes, and that these waves behave much like SPPs do in the visible range. • Daniel M. Mittleman, Electrical and Computer Engineering Department., Rice University, ­Houston, Texas—Daniel Mittleman’s group first proposed the use of cylindrical metal wires for terahertz plasmonic waveguides. He showed that such waveguides supported long distance propagation with very limited dispersion. This group has continued to extend its understanding of this system. For example, it has studied better methods of coupling terahertz radiation with the wire (Deibel et al., 2006). • Paul C.M. Plancken, Delft University of Technology, Delft, The Netherlands—Dr. Plancken’s group has also studied the cylindrical wire system as a terahertz waveguide and has extended this study to include metallic wires coated in a dielectric. The group has found that the relatively low dispersion of the metallic wire dramatically increases in this situation. It has suggested using this property for many types of sensing applications. References Andrew, P., and W.L. Barnes. 2004. Energy transfer across a metal film mediated by surface plasmon polaritons. Science 306(5698):1002-1005. Anger, Pascal, Palash Bharadwaj, and Lukas Novotny. 2006. Enhancement and quenching of single-molecule fluorescence. Physical Review Letters 96(11):113002. Berini, Pierre, and Junjie Lu. 2006. Curved long-range surface plasmon-polariton waveguides. Optics Express 14(6): 2365‑2371. Bishnoi, Sandra W., Christopher J. Rozell, Carly S. Levin, Muhammed K. Gheith, Bruce R. Johnson, Don H. Johnson, and Naomi J. Halas. 2006. All-optical nanoscale pH meter. Nano Letters 6(8):1687-1692. Biteen, Julie S., Nathan S. Lewis, Harry A. Atwater, Hans Mertens, and Albert Polman. 2006. Spectral tuning of plasmon- enhanced silicon quantum dot luminescence. Applied Physics Letters 88(13):131109. Bjerke, Amy E., Peter R. Griffiths, and Wolfgang Theiss. 1999. Surface-enhanced infrared absorption of CO on platinized platinum. Analytical Chemistry 71(10):1967-1974. Chu, K.C., C.Y. Chao, Y.F. Chen, Y.C. Wu, and C.C. Chen. 2006. Electrically controlled surface plasmon resonance frequency of gold nanorods. Applied Physics Letters 89(10):103107. Cubukcu, Ertugrul, Eric A. Kort, Kenneth B. Crozier, and Federico Capasso. 2006. Plasmonic laser antenna. Applied Physics Letters 89(9):093120. Danckwerts, Matthias, and Lukas Novotny. 2007. Optical frequency mixing at coupled gold nanoparticles. Physical Review Letters 98(2):026104. Deibel, Jason A., Kanglin Wang, Matthew D. Escarra, and Daniel M. Mittleman. 2006. Enhanced coupling of terahertz radia- tion to cylindrical wire waveguides. Optics Express 14(1):279-290. Dintinger, José, Istvan Robel, Prashant V. Kamat, Cyriaque Genet, and Thomas W. Ebbesen. ���������������������������� 2006. Terahertz all-optical m ­ olecule-plasmon modulation. Advanced Materials 18(13):1645-1648. Drachev, V.P., V. Nashine, M.D. Thoreson, E.N. Khaliullin, D. Ben-Amotz, V.J. Davisson, and V.M. Shalaev. 2004. Adaptive silver films for bio-array applications. Paper read at 17th Annual Meeting of the IEEE Lasers and Electro-Optics Society, November 7-11, 2004, Rio Grande, Puerto Rico. Enders, D., and A. Pucci. 2006. Surface enhanced infrared absorption of octadecanethiol on wet-chemically prepared Au nanoparticle films. Applied Physics Letters 88(18):184104. Galitonov, G., S. Birtwell, N. Zheludev, and H. Morgan. 2006. High capacity tagging using nanostructured diffraction barcodes. Optics Express 14(4):1382-1387. Gao, Hanwei, Joel Henzie, and Teri W. Odom. 2006. Direct evidence for surface plasmon-mediated enhanced light transmission through metallic nanohole arrays. Nano Letters 6(9):2104-2108. García-Vidal, F.J., L. Martin-Moreno, Esteban Moreno, L.K.S. Kumar, and R. Gordon. 2006. Transmission of light through a �������������������������������������� single rectangular hole in a real metal. Physical Review B (Condensed Matter and Materials Physics) 74(15):153411. Genov, D.A., A.K. Sarychev, V.M. Shalaev, and A. Wei. 2004. Resonant field enhancements from metal nanoparticle arrays. Nano Letters 4(1):153-158. 

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APPENDIX D 217 Nikolajsen, Thomas, Kristjan Leosson, and Sergey I. Bozhevolnyi. 2004. Surface plasmon polariton based modulators and switches operating at telecom wavelengths. Applied Physics Letters 85(24):5833-5835. Noginov, M.A., G. Zhu, M. Bahoura, J. Adegoke, C.E. Small, B.A. Ritzo, V.P. Drachev, and V.M. Shalaev. 2006. Enhancement of surface plasmons in an Ag aggregate by optical gain in a dielectric medium. Optics Letters 31(20):3022-3024. Ocelic, Nenad, Andreas Huber, and Rainer Hillenbrand. 2006. Pseudoheterodyne detection for background-free near-field spectroscopy. Applied Physics Letters 89(10):101124. Okamoto, Koichi, Isamu Niki, Alexander Shvartser, Yukio Narukawa, Takashi Mukai, and Axel Scherer. 2004. Surface- p ­ lasmon-enhanced light emitters based on InGaN quantum wells. Nature Materials 3(9):601-605. O’Neal, D. Patrick, Leon R. Hirsch, Naomi J. Halas, J. Donald Payne, and Jennifer L. West. 2004. 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218 Nanophotonics Vannier, Christophe, Boon-Siang Yeo, Jeremy Melanson, and Renato Zenobi. 2006. Multifunctional microscope for far-field and tip-enhanced Raman spectroscopy. Review of Scientific Instruments 77(2):023104. Verhagen, E., A.L. Tchebotareva, and A. Polman. 2006. Erbium luminescence imaging of infrared surface plasmon polaritons. Applied Physics Letters 88(12):121121. Wang, Kanglin, and Daniel M. Mittleman. 2006. Dispersion of surface plasmon polaritons on metal wires in the terahertz frequency range. Physical Review Letters 96(15):157401. Weeber, J.C., M.U. Gonzalez, A.L. Baudrion, and A. Dereux. 2005. Surface plasmon routing along right angle bent metal strips. Applied Physics Letters 87(22):221101. Xu, Hongxing, Xue-Hua Wang, Martin P. Persson, H.Q. Xu, Mikael Kall, and Peter Johansson. 2004. Unified treatment of fluorescence and Raman scattering processes near metal surfaces. Physical Review Letters 93(24):243002. Zhang, X., M.A. Young, O. Lyandres, and R.P. Van Duyne. 2005. Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy. Journal of the American Chemical Society 127(12):4484-4489. Zhang, X., J. Zhao, A.V. Whitney, J.W. Elam, and R.P. Van Duyne. 2006. Ultrastable substrates for surface-enhanced Raman spectroscopy: Al2O3 overlayers fabricated by atomic layer deposition yield improved anthrax biomarker detection. Journal of the American Chemical Society 128(31):10304-10309.