Near-field characterization of Bragg mirrors engraved in surface plasmon waveguides

Abstract

International audienceSurface plasmon waveguides (SPW's) are metal ridges featuring widths in the micrometer range and thicknesses of a few tens of nanometers. A focused ion beam has been used to carve microscatterers into gold SPW's and the near-field distributions around these microstructures are observed by means of photon scanning tunneling microscopy (PSTM). On the basis of near-field images, we show that a finite length periodic arrangement of narrow slits can reflect a surface plasmon mode propagating along a SPW. The reflection efficiency of the micrograting is found to depend upon the number of slits, the period of the grating, and the incident wavelength. The optimum reflection efficiency is obtained for a period of the micrograting equal to half the incident wavelength in vacuum. The PSTM images of the plasmon mirrors taken at different wavelengths allow us to measure the experimental dispersion curve of the SPW in the near-infrared. From this dispersion curve, we found that, in analogy with a surface plasmon (SP) excited on extended thin films, the group velocity of a SPW mode is close to the speed of light. For a given frequency in the near-infrared, the effective index of the SP mode supported by a 2.5-mum-wide SPW is also found to be significantly larger than the effective index of an extended thin film SP. Finally, we show that the optical properties of microgratings engraved into a SPW can be qualitatively approached by a standard Bragg mirror model

Design of plasmon cavities for solid-state cavity quantum electrodynamics applications

“…Moreover, another group has proposed coupling emitters to metallic nanowires and nanotips to enhance Purcell factors [3]. By employing SP cavities in solid-state, we could attempt to achieve the same or even higher SE rate enhancement as with previous designs, but with simplified fabrication.Several authors have demonstrated decreased transmission by using periodic structures to manipulate SPs [4,5].These experiments confirm the existence of backscattering and a plasmonic band gap in metallic gratings. In addition, other groups have demonstrated that surface plasmons interfere as normal waves and set up standing waves under certain conditions [6].…”

Scattering of surface plasmon polaritons by one-dimensional inhomogeneities

“…1,2 As a result of such a study, phenomena like total suppression of reflection, 3 transformation of polarization, [4][5][6] enhanced light transmission, 7,8 formation of band gaps [9][10][11][12] and other interesting properties of plasmonic crystals have been discovered. Lately, a great deal of attention has been devoted to the creation of optical elements for SPP's, [13][14][15][16][17] as well as to the efficient coupling of light into and out of SPP's. These latter problems require a precise knowledge of the scattering coefficients of the dispersion centers ͑i.e., deviations from a flat metal-dielectric interface͒ placed on the path of SPP's.…”

Low-frequency active surface plasmon optics on semiconductors

“…This gap is a consequence of the Bragg scattering of SPPs. [13][14][15][16] The upper band intercepts the light line at = 0.335 THz. At higher frequencies, SPPs become leaky waves, thus being coupled by the grating to freely propagating electromagnetic radiation.…”

“…8 As the temperature is lowered, the density of thermally excited carriers is reduced and their mobility increases. At −35°C, N Ӎ 0.3ϫ 10 16 We use a THz-time domain spectrometer capable of measuring the amplitude of the THz field as function of time. In this setup, a train of ultrashort optical pulses from a Ti-:Sapphire laser is split into two beams.…”