M. Spajer

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.

Near field optics: Snapshot of the field emitted by a nanosource using a photosensitive polymer

We propose here a method for probe characterization based on lithography on a photosensitive polymer without film development. We record in near field conditions the light emitted by different kinds of probes in order to distinguish in situ the near field contribution from the far field contribution of the tip. This information, which cannot be deduced from far field diffraction, allows an estimation of the field confinement and of the expected resolution of the microscope.

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.

Imaging of submicron index variations by scanning optical tunneling

The scanning tunneling optical microscope (SNOM, STOM, PSTM, etc.) is the equivalent of the electron scanning tunneling microscope in the electromagnetic domain. Although it was born at the same time, its actual development is more recent. Here, some new results obtained with the version working in total reflection (STOM/PSTM) are reported. A grating of a periodicity of 417 nm and a thickness of 5 nm have been imaged both in TM and TE modes. It is first noted that the optical image is well resolved. Furthermore, the difference of behavior of the field versus the polarization of the incident light has been shown. More precisely, the TM mode seems to be highly sensitive to small index and topography variations due to surface contaminants. Such effects are generally not imaged by atomic force microscopy working in attractive mode, because they affect the surface topography slightly. The SNOM could be thus a very powerful tool for detecting pollutants over the surface of objects like glasses, lenses, gratings...

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.

Piezoelectric shear force detection: A geometry avoiding critical tip/tuning fork gluing

A technique for controlling the tip–sample distance in near-field optical microscopes is presented. It consists of mechanically exciting a fiber tip inserted without any adhesive between the two prongs of a high Q-piezoelectric tuning fork. The detection of the shear forces is classically achieved by measuring the decrease of the dithering amplitude when the tip approaches the surface. This simple setup greatly simplifies tip replacement and its resonance frequency tuning.

Nanospectrofluorometry inside single living cell by scanning near-field optical microscopy

Near-field fluorescence spectra with subdiffraction limit spatial resolution have been taken in the proximity of mitochondrial membrane inside breast adenocarcinoma cells (MCF7) treated with the fluorescent dye (JC-1) by using a scanning near-field optical microscope coupled with a confocal laser microspectrofluorometer. The probe–sample distance control is based on a piezoelectric bimorph shear force sensor having a static spring constant k=5 μN/nm and a quality factor Q=40 in a physiological medium of viscosity η=1.0 cp. The sensitivity of the force sensor has been tested by imaging a MCF7 cell surface.

Visualization of latent images by reflection near field optical microscopy

Abstract Near field reflection imaging on non-developed photoresists is achieved using a dielectric probe. Preliminary results demonstrate a subwavelength resolution uncorrelated with topographic image and a contrast related to the index change integrated on the layer thickness.

Step towards sum frequency generation spectromicroscopy at a submicronic spatial resolution

A near-field optical device has been developed to collect sum frequency signal, generated in an AsGa single crystal sample by two pulsed lasers, one fixed at a wavelength of 532 nm and the other tunable in midinfrared. The sum frequency signal was collected with an uncoated silica tip. When the tip sample distance was increased, a strong decrease of the collected sum frequency signal was observed: the signal was divided by 2 for an increase of about 100 nm of the distance between the nanoprobe end and the sample surface. Without demonstrating submicronic lateral spatial resolution, this letter is, however, a first step towards a microscopic device of sum frequency generation spectroscopy.

Linear phase detection for a bimodal fiber sensor

Interference between the LP(01) and LP(02) modes is used to measure fiber elongation. We present a passive phase-detection technique that uses a mask in the far field of the output beam and spatial filters in the image of the fiber end face, giving a linear response. Experimental results show a precision of about 3% of one period, which corresponds to a 4-microm elongation.