A simple method for producing flattened atomic force microscopy tips.

We describe a simple and reliable procedure for obtaining a flat plateau on top of standard silicon nitride atomic force microscopy tips by scanning them over the focus of a high-numerical-aperture objective illuminated by near-infrared ultrashort laser pulses. Flattened tips produced this way exhibit a plateau that is parallel to the substrate when the cantilever is mounted. They represent a valid and cost-effective alternative to commercially available plateau tips.

Single quantum dot coupled to a scanning optical antenna: a tunable superemitter.

The interaction of a single quantum dot with a bowtie antenna is demonstrated for visible light. The antenna is generated at the apex of a Si3N4 atomic force microscopy tip by focused ion beam milling. When scanned over the quantum dot, its photoluminescence is enhanced while its excited-state lifetime is decreased. Our observations demonstrate that the relaxation channels of a single quantum emitter can be controlled by coupling to an efficiently radiating metallic nanoantenna.

Resonant optical antennas.

We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations that take into account the finite metallic conductivity at optical frequencies. Because optical antennas link propagating radiation and confined/enhanced optical fields, they should find applications in optical characterization, manipulation of nanostructures, and optical information processing.

Optics at the nanometre scale.

The development of nano-optics is reviewed, with emphasis on its historical roots and up to the time when it became an established branch of nanometre science and technology. It concentrates on the decade 1984-1994, and in particular on the principally new ideas that came up during that period. A special focus is scanning near-field optical microscopy, which still is the most active part of nano-optics research (aside from being the author's field of specialization). No attempt is made to review scientific development after 1994 in a systematic way, since it is well represented by the other articles presented in this Theme issue.

Propagation and diffraction of locally excited surface plasmons.

With the use of optical near-field techniques, it is now possible to excite or observe surface plasmons with high lateral resolution. A theoretical study is presented of surface plasmon excitation by near-field optical probes and the influence of well-defined structures on surface plasmon propagation and surface plasmon detection in the far field. The generation and the diffraction of the surface plasmon is calculated by using a theoretical scheme founded upon a first-order perturbation expansion of the Rayleigh-Fano method. A very good agreement is obtained between numerical and experimental results. The theoretical tools used should prove a useful guideline for future experiments of nanooptics with surface plasmons.

Plasmon transmissivity and reflectivity of narrow grooves in a silver film.

Surface plasmon (SP) reflectivity and transmissivity of narrow grooves in silver films are studied. The SP source is the probe of a scanning near-field optical microscope. Locally detected leakage radiation from the SP provides detailed information on the paths of SP propagation, in particular the influence of perturbations. Global detection provides representative average data on the SP properties of a given metal film and its structures. A groove of 200 nm width, for instance, reflects/transmits about 15%/80% of 'blue-green' SP radiation at normal incidence.

Laser-Induced Phase Transition in the Surface of SmS Crystals.

Localized annihilation and generation of the metallic surface phase of SmS was obtained with short laser pulses. Small spot sizes and a large difference in reflectivity suggest an application for optical data storage.