D. Courjon

An all-fiber device for generating radially and other polarized light beams

Radially polarized beams are beams for which the electric vector is radially distributed along the beam axis. Such beams are interesting for applications in which a total symmetry of the electric field is required. In this paper we propose an all-fiber method allowing the generation of radially, azimuthally, and hybrid polarized light beams in a rapid and simple way.

Bessel beams as virtual tips for near-field optics.

In the previous NFO meeting, we proposed the use of confined evanescent light beams as ‘virtual’ or ‘immaterial’ tips. Unfortunately, this technique was hindered by the need for perfectly radially polarized light beams. In this communication, we propose a simple, stable and cheap method allowing the generation of beams of any polarization and more especially of purely radially polarized light beams. We also demonstrate both theoretically and experimentally that for near‐field imaging systems polarization is a limiting factor of resolution and light confinement. Finally, we present the very first experimental results dealing with virtual tips.

Influence of the water layer on the shear force damping in near-field microscopy

The influence of the water layer on the shear force damping is investigated in the case of a perfectly flat mica surface. In ambient conditions it is shown that the damping curve exhibits three particular regimes depending on the tip-sample distance. Moreover, the damping varies significantly over the first hour, pointing out the complexity of the distance control by shear force detection.

Smallest lithographic marks generated by optical focusing systems.

We show that the combination of Bessel beams and photosensitive materials exhibiting polarization filtering properties allows one to reach the smallest mark that can be lithographically generated by focusing systems. This property is of interest in current optical data storage techniques.

A theoretical model for the Inverse Scanning Tunneling Optical Microscope (ISTOM)

Abstract Recently experiments have been performed with a new kind of Scanning Near-field Microscope. The apparatus is derived from a Scanning Tunneling Optical Microscope by simply inverting the direction of light propagation: it is thus an Inverted Scanning Tunneling Optical Microscope (ISTOM) where the tip is used in emission mode and where detection can be mediated via homogeneous or evanescent waves. We propose a theoretical calculation of the detected intensity measured in ISTOM experiments. In this model, the sample is a relief on the hemisphere surface and the source is an aperture tip described within the Bethe-Bouwkamp approximation. The use of plane wave expansions of the various fields and of a perturbation method for matching the boundary conditions lead to concise analytical formulas. The discussion of the influence of the various parameters on the detected intensity is thus quite easy. We illustrate the formulas by some examples showing the variations of the detected signal versus tip-surface distance, tip radius and detection angle.

Novel spectromicroscopy: Pt–GaP studies by spatially resolved internal photoemission with near‐field optics

The combination of internal photoemission and near‐field optics is proposed as a generally applicable approach to study the lateral variations of solid interface properties such as energy barriers and electron‐hole recombination rates. A successful test on Pt–GaP is described in which topographic and nontopographic phenomena are revealed, in particular recombination rate variations and small lateral changes of the Schottky barrier height.

Seeing inside a Fabry-Pérot resonator by means of a scanning tunneling optical microscope

Abstract By integrating a scanning tunneling optical microscope inside a Fabry-Perot resonator, it is possible to map very precisely the structure of the electromagnetic field inside the resonant cavity. Moreover, by working in antiresonant mode (dark field conditions), it is possible to locally remove the incident evanescent field. This particular configuration increases the z -resolution in such microscopes.

USE OF SOLID ELECTROLYTIC EROSION FOR GENERATING NANO-APERTURE NEAR-FIELD COLLECTORS

A new way in the fabrication of metallized nano-apertures for near-field optical microscopy is proposed. The method is based on the electrolysis between a silver metallized probe and an electrolytic glass. By dry electrolytic erosion, the metal on the tip apex is removed and lead to a very small metal free aperture. This method applied here to tapered fibers, can be extended to any other metallized tip in a rather reproducible way.

Conical optics: the solution to confine light

We compare the performances in terms of confinement and depth of field of spherical and conical optics. It turns out that, if the spherical optics is adapted to the usual parallel imaging, conical optics seems to be the optimized solution for systems based on scanning (sequential imaging). It is shown that the optimized confinement capability of conical optics is due to the ability of conical components to generate a single Bessel beam with high efficiency. The calculations are based on Weyl formulas.

Annular nanoantenna on fibre micro-axicon.

In this paper, we propose to extend the concept of loop antenna to the optical domain. The aim is to develop a new generation of optical nanocollectors that are sensitive to specific electric or magnetic vectorial field components. For validating our approach, a preliminary one‐micron‐diameter gold nanoring is micromachined on the apex of a cone lens obtained from a tapered optical fibre. It is shown that such a nano‐object behaves as a nano‐antenna able to detect the longitudinal electric field from a Bessel beam in radial polarization and the longitudinal magnetic component from a Bessel beam in azimuthal polarization. In the latter case, the annular nano‐antenna exhibits the properties of an optical inductance.