Biomedical subjects

V Sandoghdar

Publications and source records attributed to V Sandoghdar.

11 recordsLinked to original sources

PubMed2001

Apertureless near-field optical microscopy via local second-harmonic generation.

We describe an apertureless scanning near-field optical microscope (SNOM) based on the local second-harmonic generation enhancement resulting from an electromagnetic interaction between a probe tip and a surface. The imaging mechanisms of such apertureless second-harmonic SNOM are numerically studied. The technique allows one to achieve strongly confined sources of second-harmonic light at the probe tip apex and/or surface area under the tip. First experimental realization of this technique has been carried out using a silver-coated fibre tip as a probe. The experiments reveal a strong influence of the tip-surface interaction as well as polarization of the excitation light on images obtained with apertureless second-harmonic SNOM. The technique can be useful for studying the localized electromagnetic excitations on surfaces as well as for visualization of lateral variations of linear and nonlinear optical properties of surfaces.

Journal Article↗

PubMed2001

A single gold particle as a probe for apertureless scanning near-field optical microscopy.

We report on the fabrication, characterization and application of a probe consisting of a single gold nanoparticle for apertureless scanning near-field optical microscopy. Particles with diameters of 100 nm have been successfully and reproducibly mounted at the end of sharp glass fibre tips. We present the first optical images taken with such a probe. We have also recorded plasmon resonances of gold particles and discuss schemes for exploiting the wavelength dependence of their scattering cross-section for a novel form of apertureless scanning near-field optical microscopy.

Journal Article↗

PubMed2001

Diamond colour centres as a nanoscopic light source for scanning near-field optical microscopy.

Recently it was shown that a single molecule at cryogenic temperatures could be used as a local light source for illumination of a sample in the near field. Conventional light-emitting systems such as dye molecules and semiconductor quantum dots could also be used for this purpose, but they suffer from lack of photostability. However, colour centres in diamond have been found to be remarkably stable against bleaching and blinking effects. Here we present the first SNOM images taken with nanoscopic diamond crystals as a light source.

Journal Article↗

PubMed2001

Mapping and manipulating whispering gallery modes of a microsphere resonator with a near-field probe.

We report high spatial resolution mapping of high-Q whispering gallery modes in microsphere resonators with a near-field probe. We present experimental results on the effect of Q-factor degradation when the probe interacts with the evanescent field and discuss future applications of our experimental set-up for realization of novel nanolasers and nano light-emitting-diodes.

Journal Article↗

PubMed2000

Optical microscopy using a single-molecule light source

Rapid progress in science on nanoscopic scales has promoted increasing interest in techniques of ultrahigh-resolution optical microscopy. The diffraction limit can be surpassed by illuminating an object in the near field through a sub-wavelength aperture at the end of a sharp metallic probe. Proposed modifications of this technique involve replacing the physical aperture by a nanoscopic active light source. Advances in the spatial and spectral detection of individual fluorescent molecules, using near-field and far-field methods, suggest the possibility of using a single molecule as the illumination source. Here we present optical images taken with a single molecule as a point-like source of illumination, by combining fluorescence excitation spectroscopy with shear-force microscopy. Our single-molecule probe has potential for achieving molecular resolution in optical microscopy; it should also facilitate controlled studies of nanometre-scale phenomena (such as resonant energy transfer) with improved lateral and axial spatial resolution.

Journal Article↗

PubMed1996