Search results for "Near-field optic"
showing 10 items of 49 documents
Diffractive optics for processing ultrashort light pulses
2011
In this work we combine, in principle, two disjoint optical fields, diffractive optics and ultrashort light radiation. This combination allows us to manipulate in a very unconventional manner femtosecond pulses and, on the other hand, to implement a set of novel applications. In our case we have focused our attention on material processing and biophotonics applications.
Applications of near-field optics to the characterization of optoelectronics components
1997
In the race towards purely optical communications, the necessity of producing integrated components is linked to the requirement for the precise characteriza-tion of optoelectronic components. Near-field detection techniques meet this requirement, AFM (Atomic Force Microscopy), for instance, can provide the topography of a given sample. In conjunction with these new tools, several different kinds of near-field optical microscopes (NFOM) have appeared. They enable the characteriza-tion of the components with a resolution better than that imposed by the Rayleigh criterion. This is primarily due to the fact that they are sensitive to the evanescent waves. This document presents several areas r…
Near-field optical response of a two-dimensional grating of gold nanoparticles
2001
Laboratoire de Physique, Optique Submicronique, Universite´de Bourgogne, Boite Postale 47870, F-21078 Dijon, France~Received 1 August 2000; published 4 April 2001!This article reports on the near-field optical response of a small square grating of gold nanoparticles tailoredby electron-beam lithography. The investigation of the grating is aimed at a deepened understanding ofelectromagnetic interaction among particles due to scattered light fields. Therefore, a photon scanning tunnel-ing microscope is applied to acquire near-field optical images. Two different incident wavelengths are used tocharacterize the intensity and the spatial localization of the electromagnetic near field both in and out…
Simultaneous observation of light localization and confinement in near-field optics
2001
We report on the observation, in direct space, of both light localization and confinement effects near lithographically designed structures. The sample is observed in the optical near-field zone with a Photon Scanning Tunneling Microscope (PSTM). Several patterns composed of a few periods of TiO2 dots, arranged as a hexagonal lattice, have been investigated. When the central dot of the pattern is removed, a phenomenon of light localization above the vacancy can be observed in the PSTM image. The occurrence of this phenomenon can be related to the variation of the electromagnetic local density of state.
Near-field optics theories
1996
The development of near-field optics theory is reviewed. We first recall that near-field optics is not limited to near-field microscopy. Broadly speaking, it concerns phenomena involving evanescent electromagnetic waves. The importance of such waves was ignored for a long time in optical and surface physics until the emergence of scanning near-field optical microscopes. Taking evanescent waves into account prevents the use of any simple approximation in the set of Maxwell's equations. The various theoretical approaches of near-field optics are discussed from the point of view of their ability to assess evanescent electromagnetic waves. We discuss the main results of the application of the v…
Resonant optical tunnel effect through dielectric structures of subwavelength cross sections.
1998
We show that optical tunnel effects through elongated structures of subwavelength cross sections can be enhanced by the appropriate structuration of the local dielectric function. Even under total internal reflection, transfer channels can be excited to perform spatially confined photonic transfer between transparent media linked by such subwavelength structures. The optical properties of such systems are analyzed using field susceptibilities, also known as electromagnetic Green's dyadics, which determine both the local density of photon states and the optical transmittance of the system. Green's dyadics obtained by solving numerically a set of dyadic Dyson equations are applied to study th…
Photonic transfer through subwavelength optical waveguides
1998
Optical tunneling effect through dielectric junctions with subwavelength transverse sizes has been demonstrated some years ago. In this letter, we demonstrate how similar effects can be exploited to perform photonic transfer through a subwavelength optical wave guide (SOW) by structuring its optical index along the direction of propagation. The optical transmittance of the SOW is computed self-consistently in direct space through the numerical solution of a Dyson equation. We apply this scheme to investigate the optical properties of different SOW architectures. Even under total internal reflection, in which the light is coupled to the SOW by an evanescent mode, an efficient optical transfe…
Modelling Optical Resonators Probed by Subwavelength Sized Optical Detectors
1996
The possibility of mapping the optical field structure inside a Fabry-Perot resonator by using a pointed optical fiber was recently reported [1]. In this contribution, we propose a simulation of such near-field optical experiments by using a two-dimensional self-consistent model. The method based on the discretization of four different domains, i.e. the two mirrors, the glass sample and the tip, allows us a meaningful description of the evolution of the full field pattern when approaching the optical detector. In particular, this computerized work supply a direct illustration of the optical energy tranfer occurring when the tip enters the near-field zone. In this context, different tip desi…
Reflection scanning microscopy.
1992
To image nontransparent samples we have utilized a special type of scanning-probe microscope that is referred to here as a reflection scanning microscope. The reflection scanning microscope provides a method for producing a scanned point light source as well as a system for collecting the light that is reflected by the sample. The system, which uses an optical fiber coupler, is easily installed on an existing photon scanning tunneling microscope. A calculation of the coupling coefficient between the natural propagation mode of the optical fiber and the light that is reflected by the sample is presented along with a comparison between calculated and measured values of the intensity of the li…
Optical near-field microscopy of light focusing through a photonic crystal flat lens
2008
We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.