Biomedical subjects

S Huant

Publications and source records attributed to S Huant.

At least 19 recordsLinked to original sources

PubMed2001

Far-field emission of a tapered optical fibre tip: a theoretical analysis.

The far-field transmission pattern of a tapered optical tip with small aperture (radius approximately < 40 nm) is modelled by solving Maxwell's equations in the radiation zone with boundary conditions appropriate to the conical geometry. The model is able to reproduce the large differences between the S and P polarizations observed previously in the emission profile of such a tip [Obermüller and Karrai. Appl. Phys. Lett. (1995) 67, 3408].

Journal Article↗

PubMed2001

Low-temperature near-field spectroscopy of CdTe quantum dots.

A near-field optical microscope has been developed for operation at low temperature. This microscope is used to study the photoluminescence of CdTe-based quantum dots. Spectra collected upon approaching the optical tip into the near-field region of the sample reveal the evolution from a broad far-field luminescence band - that is typical for a large ensemble of dots - to a near-field structure made up of a few sharp peaks originating from individual dots. Experiments carried out in the excitation-collection mode through the optical tip allow study of the effect of an increase in excitation power on the near-field spectra. It is found that upon increasing the excitation by two orders of magnitude, a spatially resolved spectrum progressively transforms back into a broad 'far-field-like' spectrum. Photoluminescence images taken by scanning the sample under the tip are used to discriminate various contributions coming from individual dots.

Journal Article↗

PubMed2001

Near-field optics on silicon-electrolyte junctions.

A technique allowing near-field photocurrent (PC) mapping of silicon surfaces in contact with an electrolyte is presented. The illumination source is an optical fibre tip with a 100-nm aperture. A shear force detection system controls the tip-sample distance while scanning the tip across the silicon-electrolyte interface. Topographic and PC images on SiO2/Si mesas both show 300 nm resolution. It is shown that this PC contrast is induced by the tip-topography interaction and hence the PC resolution is limited by the resolution of the topography. Indeed, PC mapping on topography-less patterned porous-silicon/silicon samples shows that the lateral resolution is only limited by the aperture size which is of the order of 100 nm.

Journal Article↗

PubMed1996