Query: Time-domain measurements of surface plasmon polaritons in the terahertz frequency range

Candidate papers:

abstract: Surface plasmon polaritons ~SPP's at metal dielectric interfaces have proven to be a reliable technique for the investigation of thin films, allowing to derive properties such as optical and dielectric constants, film thickness, and inhomogeneities at interfaces with high precision ~for an overview see Ref. 1! Additionally, it has been discovered recently that SPP's play a crucial role in the extraordinary high transmission of light through arrays of sub wavelength holes. 2,3 Thanks to SPP's light can be concentrated and controlled over length scales much smaller than the wavelength. As a result, a new and promising research field known as plasmonics has emerged, one of its primary goals being the fabrication of nanoscale photonic circuits. 4 With the development of short pulse lasers terahertz ~THz! spectroscopy has opened up an interesting but hardly accessible spectral window where a large variety of gases, liquids, and solids show specific resonances. THz applications range from studies of coherent excitations in semiconductor heterostructures to medical diagnostics and threedimensional imaging systems for monitoring industrial processes. 5,6 Key biological constituents such as proteins, ribonucleic acids, and deoxyribonucleic acids have resonances at THz frequencies, 7 10 which makes THz radiation of keen interest for direct and simple biosensing. The latter often involves the analysis of typically very thin biomolecular films. Surface plasmon polariton~SPP! spectroscopy at THz frequencies has a large potential for biosensing applications, providing high electromagnetic field strengths in the films together with long interaction lengths. 1 In spite of these important advantages almost no work has been done so far on SPP's in the THz frequency range. 11 In this paper we present the first time domain THz study of SPP's on metal surfaces and metals covered with dielectric films. The broadband character of our THz setup allows us to obtain information over a wide range of frequencies between 0.2 and 2 THz in a single measurement. As we will show, small changes on the film thickness relative to the THz wavelength lead to drastic modifications on the SPP's field distribution and spectrum. These modifications demonstrate the capabilities of terahertz SPP's for sensitive spectroscopy of thin films. Figure 1~a! illustrates the field geometry used for exciting SPP's. A semi infinite dielectric and a semi infinite metal define an interface at z50. A p polarized electromagnetic wave incident from the (y,z) plane is coupled into a surface evanescent wave traveling in the y direction along the interface and decaying exponentially into both media. The magnetic field of the SPP's in the dielectric has the form H( y,z,t)5exp(iky2ivt)U e (z)e x with the envelope function 12 Ue~ z!5A1e 2b1z z.0 ~1! where b5Ak 2 2< d v 2 /c 0 ~2! is the SPP decay constant normal to the interface into the dielectric, k is the SPP wave vector, v is the SPP frequency, c 0 is the vacuum speed of light, and d is the permittivity of the dielectric which is given by the complex quantity d 5< d1i< d The decay length L of the SPP's into the dielectric is given by FIG. 1. ~a! Schematic of the SPP's incoupling geometry. An electromagnetic wave ~wave vector kinc) is incident at a angle f 567deg onto the interface z50 defined by medium 1~dielectric! and medium 2 ~metal! The electric field vector Einc lies in the plane of incidence, whereas Hinc is along x direction! ~b! Experimental setup ~not to scale! used for exciting SPP's on a gold film of 300 nm thickness covered with a dielectric film of thickness d. The incoming THz beam is focused on the incoupling aperture h1 which is defined by razor blade K1 and the surface of the dielectric. The THz spot diameter at the focus is approximately 1 mm. The SPP's travel along the sample interface until scattered at the outcoupling aperture h2. The incoupling and outcoupling apertures h1 and h2 can be individually varied from 0 to 10 mm by changing the height of K1 and K2, respectively. The distance Dy between K1 and K2 defines the SPP's longitudinal propagation distance. PHYSICAL REVIEW B 69, 155427 ~2004!
author_names: J Saxler

Jaime Gomez Rivas

Christof Janke

H P M Pellemans

Peter Haring Bolivar

H Kurz
title: Time domain measurements of surface plasmon polaritons in the terahertz frequency range
year: 2004

abstract: A surface plasmon polariton (SPP) is an electromagnetic excitation existing on the surface of a good metal. It is an intrinsically two dimensional excitation whose electromagnetic field decays exponentially with distance from the surface. In the past, it was possible to study only the (far field) scattered light produced by the interaction of surface polaritons with surface features. Only with the development of scanning near field optical microscopy did it become possible to measure the surface polariton field directly in close proximity to the surface where the SPP exists. Here we overview the near field studies of surface polaritons on randomly rough and nanostructured surfaces, theoretical models of SPP interaction with surface features, and SPP applications in novel photonic technologies. Surface polariton scattering, interference, backscattering, and localization will be discussed, as well as concepts of surface polariton optics and polaritonic crystals. Surface polaritons are finding an ever increasing number of applications in traditional domains of surface characterization and sensors as well as in newly emerging nano photonic and optoelectronic technologies.
author_names: Anatoly V Zayats

Igor I Smolyaninov

Alexei A Maradudin
title: Nano optics of surface plasmon polaritons
year: 2005

abstract: We report the experimental and theoretical study of the dispersive behavior of surface plasmon polaritons (SPPs) on cylindrical metal surfaces in the terahertz frequency range. Time domain measurements of terahertz SPPs propagating on metal wires reveal a unique structure that is inconsistent with a simple extrapolation of the high frequency portion of the dispersion diagram for SPPs on a planar metal surface, and also distinct from that of SPPs on metal nanowires observed at visible and near infrared frequencies. The results are consistent with a numerical solution of Maxwell's equations, showing that the dispersive behavior of SPPs on a cylindrical metal surface at terahertz frequencies is quite different from that of SPPs on a flat surface. These findings indicate the increasing importance of skin effects for SPPs in the terahertz range, as well as the enhancement of such effects on curved surfaces.
author_names: Kanglin Wang

Daniel M Mittleman
title: Dispersion of surface plasmon polaritons on metal wires in the terahertz frequency range.
venue: Physical review letters
year: 2006

abstract: Collective electronic excitations at metal surfaces are well known to play a key role in a wide spectrum of science, ranging from physics and materials science to biology. Here we focus on a theoretical description of the many body dynamical electronic response of solids, which underlines the existence of various collective electronic excitations at metal surfaces, such as the conventional surface plasmon, multipole plasmons and the recently predicted acoustic surface plasmon. We also review existing calculations, experimental measurements and applications.
author_names: Jose M Pitarke

Viatcheslav M Silkin

Eugene V Chulkov

Pedro Miguel Echenique
title: Theory of surface plasmons and surface plasmon polaritons
year: 2007

abstract: Metals such as silver support surface plasmons: electromagnetic surface excitations localized near the surface that originate from the free electrons of the metal. Surface modes are also observed on highly conducting surfaces perforated by holes. We establish a close connection between the two, showing that electromagnetic waves in both materials are governed by an effective permittivity of the same plasma form. The size and spacing of holes can readily be controlled on all relevant length scales, which allows the creation of designer surface plasmons with almost arbitrary dispersion in frequency and in space, opening new vistas in surface plasmon optics.
author_names: John Brian Pendry

Luis Martin-Moreno

Francisco J Garcia-Vidal
title: Mimicking Surface Plasmons with Structured Surfaces
venue: Science
year: 2004

abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons in particular their interaction with light can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio photonics.
author_names: William L Barnes

Alain Dereux

Thomas W Ebbesen
title: Surface plasmon subwavelength optics
venue: Nature
year: 2003

abstract: 5.1. Detection Formats 475 5.2. Food Quality and Safety Analysis 477 5.2.1. Pathogens 477 5.2.2. Toxins 479 5.2.3. Veterinary Drugs 479 5.2.4. Vitamins 480 5.2.5. Hormones 480 5.2.6. Diagnostic Antibodies 480 5.2.7. Allergens 481 5.2.8. Proteins 481 5.2.9. Chemical Contaminants 481 5.3. Medical Diagnostics 481 5.3.1. Cancer Markers 481 5.3.2. Antibodies against Viral Pathogens 482 5.3.3. Drugs and Drug Induced Antibodies 483 5.3.4. Hormones 483 5.3.5. Allergy Markers 483 5.3.6. Heart Attack Markers 484 5.3.7. Other Molecular Biomarkers 484 5.4. Environmental Monitoring 484 5.4.1. Pesticides 484 5.4.2. 2,4,6 Trinitrotoluene (TNT) 485 5.4.3. Aromatic Hydrocarbons 485 5.4.4. Heavy Metals 485 5.4.5. Phenols 485 5.4.6. Polychlorinated Biphenyls 487 5.4.7. Dioxins 487 5.5. Summary 488 6. Conclusions 489 7. Abbreviations 489 8. Acknowledgment 489 9. References 489
author_names: Jiri Homola
title: Surface plasmon resonance sensors for detection of chemical and biological species.
venue: Chemical reviews
year: 2008

abstract: In this Letter, we show how the dispersion relation of surface plasmon polaritons (SPPs) propagating along a perfectly conducting wire can be tailored by corrugating its surface with a periodic array of radial grooves. In this way, highly localized SPPs can be sustained in the terahertz region of the electromagnetic spectrum. Importantly, the propagation characteristics of these spoof SPPs can be controlled by the surface geometry, opening the way to important applications such as energy concentration on cylindrical wires and superfocusing using conical structures.
author_names: Stefan A Maier

Steven R Andrews

Luis Martin-Moreno

Francisco J Garcia-Vidal
title: Terahertz surface plasmon polariton propagation and focusing on periodically corrugated metal wires.
venue: Physical review letters
year: 2006

abstract: Surface plasmons on smooth surfaces. Surface plasmons on surfaces of small roughness. Surfaces of enhanced roughness. Light scattering at rough surfaces without an ATR device. Surface plasmons on gratings. Conclusions.
author_names: Heinz Raether
title: Surface Plasmons on Smooth and Rough Surfaces and on Gratings
year: 1988

abstract: Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles is a powerful technique for chemical and biological sensing experiments. Moreover, the LSPR is responsible for the electromagnetic field enhancement that leads to surface enhanced Raman scattering (SERS) and other surface enhanced spectroscopic processes. This review describes recent fundamental spectroscopic studies that reveal key relationships governing the LSPR spectral location and its sensitivity to the local environment, including nanoparticle shape and size. We also describe studies on the distance dependence of the enhanced electromagnetic field and the relationship between the plasmon resonance and the Raman excitation energy. Lastly, we introduce a new form of LSPR spectroscopy, involving the coupling between nanoparticle plasmon resonances and adsorbate molecular resonances. The results from these fundamental studies guide the design of new sensing experiments, illustrated through applications in which researchers use both LSPR wavelength shift sensing and SERS to detect molecules of chemical and biological relevance.
author_names: Katherine A Willets

Richard P Van Duyne
title: Localized surface plasmon resonance spectroscopy and sensing.
venue: Annual review of physical chemistry
year: 2007