Near-field optics and plasmonics Manuel Rodrigues Gonçalves AFM topography 10 Pol. y / (µm) 8 6 4 2 0 0 2 4 6 x / (µm) 8 10 nm 60 80 100 120 140 Physik M. Sc. Master Advanced Materials Winter semester 2011/2012
From sub-wavelength optics to nano-optics Synge propose in 1928 (in a letter to Einstein) a method to resolve optically an object below the diffraction limit. E. H. Synge, "A suggested method for extending the microscopic resolution into the ultramicroscopic region", Phil. Mag. 6, 356 (1928). Ash and Nicholls have done the first measurements with lateral sub-wavelength resolution using microwaves. E.A. Ash and G. Nicholls, "Super-resolution Aperture Scanning Microscope", Nature 237, 510 (1972). Pohl, Denk and Lanz developed the first Scanning Near-Field Optical Microscope (SNOM or NSOM). D.W. Pohl, W. Denk, and M. Lanz,"Optical stethoscopy: Image recording with resolution λ/20", Appl. Phys. Lett. 44, 651 (1984). Nano-optics emerged as a new domain in optics encompassing Near-field optics, plasmonics, nano-emitters and non-classical light sources, sub-wavelength confinement of light.
Nano-optics Surface plasmon photonics Surface enhanced scattering (SERS, TERS) Light scattering Enhanced photovoltaics Extraordinary optical transmission Metamaterials Nano optics Scanning microscopy Quantum emitters Scanning Near field Optical Microscopy
Diffraction limit vs. SNOM resolution Abbe (Rayleigh) resolution d 1.22λ 2n sin(θ) D.W. Pohl, et al., "Optical stethoscopy: Image recording with resolution λ/20", Appl. Phys. Lett. 44, 651 (1984).
Nanofabricated structures: Far-field vs. near-field Confocal microscope (far-field) CONFOCAL REFL. 5 4 SNOM microscope (near-field) SNOM (light intensity) 5 4 y / (µm) 3 2 1 0 0 1 2 3 4 5 x / (µm) 50 100 a.u. y / (µm) 3 2 1 0 0 1 2 3 4 5 x / (µm) counts 600 400 200
Plasmonics in the past: the Lycurgus cup The Lycurgus cup: Late Roman Empire. 4th century AD. (With permission of the British Museum).
From surface waves to plasmonics Wood discovers anomaly in the optical spectrum of metal diffraction gratings R. W. Wood, Phil. Mag. (Ser. 6), "On a remarkable case of uneven distribution of light in a diffraction grating spectrum", 4, 396 (1902). Mie publisches the teatrise on light scattering by small particles G. Mie Beiträge zur Optik trüber Medien, speziell kolloidaler Metallösungen, Ann. der Physik, Vierte Folge, 25, 377 (1908). Zenneck and Sommerfeld study the propagation of electromagnetic waves on surfaces J. Zenneck Über die Fortpflanzung ebener elektromagnetischer Wellen längs einer ebenen Leiterfläche und ihre Beziehung zur drahtlosen Telegraphie, Ann. der Physik, 328, 846 (1907). A. Sommerfeld Über die Ausbreitung der Wellen in der drahtlosen Telegraphie, Ann. der Physik, 333, 665 (1909).
From surface waves to plasmonics Ritchie relates losses in electron beam crossing thin metal foils with surface plasmons R. H. Ritchie "Plasma losses by fast electrons in thin films", Phys. Rev., 106, 874 (1957). Otto and Kretschmann and Raether present alternative systems for excitation of surface plasmons using light A. Otto, "Excitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection", Z. für Phys., 216, 398 (1968). E. Kretschmann and H. Raether, "Radiative decay of non-radiative surface plasmons excited by light", Z. Naturforsch. A, 23A, 2135 (1968).
Modern applications of plasmonics Surface plasmon resonance based sensors Light confinement at nanostructures Light scattering mediated by surface plasmons Enhanced optical transmission on arrays of apertures High-Q systems and whispering gallery modes Surface enhanced Raman scattering
NFO and Plasmonics: Topics 1 Fundamental concepts of EM waves: scattering, propagation, focusing 2 Angular spectrum representation of EM waves 3 Near-fields and far-fields 4 Confocal microscopy and SNOM: methods, probes 5 Surface plasmon-polaritons (SPPs) 6 SPPs at small particles: Mie theory, scattering, field enhancements 7 Applications of near-field enhancements: surface enhanced Raman scattering (SERS), enhanced fluorescence, spontaneous emission enhancement 8 Simulation methods for nano-optics: DDA, FDTD, FEM, etc. 9 Plasmonic materials
Nnear-field optics and plasmonics: Lab experiments Fabrication of plasmonic nanostructures Confocal microscopy: reflection and transmission modes SNOM in illumination/transmission mode Angle-resolved spectroscopy Light scattering and surface-plasmon resonance Surface enhanced Raman scattering
Near-field optics and plasmonics: lectures Dr. Manuel Rodrigues Gonçalves Institute of Experimental Physics Room N25/5212 e-mail: manuel.goncalves@uni-ulm.de Tel.: 0731 50 23022 Fax.: 0731 50 23036