High resolution imaging of dielectric surfaces with an evanescent field optical microscope

An evanescent field optical microscope (EFOM) is presented which employs frustrated total internal reflection o­n a localized scale by scanning a dielectric tip in close proximity to a sample surface. High resolution images of dielectric gratings and spheres containing both topographic and dielectric information have been obtained. The resolution obtained is 30 nm in the lateral directions and 0.1 nm in height depending o­n proper tip fabricatio

Optical contrast in near-field techniques

In this paper results of experiments with a scanning near-field optical microscope with shear-force feedback are presented. The setup will be described and the shear-force signal as function of distance is shown. Images of latex spheres and Langmuir- Blodgett layers of pentacosa-acid with about 100 nm lateral resolution are presented which show a true optical contrast due to fluorescence and polarization

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Mechanical, Maritime and Materials Engineerin

Determination of Hyperpolarizability Tensor Components by Depolarized Hyper Rayleigh Scattering

Depolarized hyper Rayleigh scattering of para-nitroaniline (C2v symmetry) and nitrocalix[4]arene (C4v symmetry) in solution has been measured. Using linearly and circularly polarized fundamental radiation information about the ratios between the several hyperpolarizability tensor components, including their sign, was obtained. Results are consistent with the theory developed for both symmetry groups. Comparison between experimental depolarization ratios and ratios obtained from ab initio calculated hyperpolarizability tensor components shows good agreement

Cerenkov-type second-harmonic generation in thin planar calix[4]arene waveguiding films

A new type of organic molecule, calix[4]arene, is applied in a second-harmonic-generating waveguide device for the first time. Linear optical properties of the calix[4]arene waveguiding film have been measured with the prism-coupling method. The molecules in the film are oriented by a corona-poling technique. With a Maker-fringe experiment, the induced d(33) and d(31) at lambda = 1064 nm are determined at 8.6 and 2.0 pm/V, respectively. The calix[4]arene thin film has been applied to a Cerenkov-type device that generates second- harmonic light radiating into the glass substrate. The highest efficiency obtained is 0.23% for a fundamental wavelength of 820 nm by the use of fundamental power densities of 100 MW/cm(2) in the waveguide and a device length of 6 mm. A coupled-mode theory has been developed that can properly explain the experimentally observed second-harmonic-generating efficiency and the angle of radiation into the substrate. Two methods for the enhancement of device efficiency are proposed, both based o¿n theoretical calculations with the coupled-mode theory. An enhancement of 2 orders of magnitude is feasible. (C) 1995 Optical Society of America

An evanescent-field optical microscope

The classic diffraction limit of resolution in optical microscopy (∼γ/2) can be overcome by detecting the diffracted field of a submicrometre‐size probe in its near field. The present stage of this so‐called scanning near‐field optical microscopy (SNOM) is reviewed. An evanescent‐field optical microscope (EFOM) is presented in which the near‐field regime is provided by the exponentially decaying evanescent field caused by total internal reflection at a refractive‐index transition. A sample placed in this field causes a spatial variation of the evanescent field which is characteristic for the dielectric and topographic properties of the sample. The evanescent field is frustrated by a dielectric probe and thus converted into a radiative field. In our case the probe consists either of an etched optical fibre or of a highly sharpened diamond tip. The probe is scanned over the sample surface with nanometre precision using a piezo‐electric positioner. The distance between probe and sample is controlled by a feedback on the detected optical signal. The resolution of the microscope is determined by both the gradient of the evanescent field and the sharpness of the tip. Details of the experimental set‐up are discussed. The coupling of the evanescent field to the submicrometre probe as a function of probe‐sample distance, angle of incidence and polarization has been characterized quantitatively. The observed coupling is generally in agreement with presented theoretical calculations. Microscopy has been performed on a regular latex sphere structure, which clearly demonstrates the capacity of the evanescent‐field optical microscope for nanometre‐scale optical imaging. Resolution is typically 100 nm laterally and 10 nm vertically. The technique is promising for biological applications, especially if combined with optical spectroscopy