Dispersion of the ordinary and extraordinary indices of refraction have been measured systematically for wurtzitic Al x Ga 1Ϫx N epitaxial layers with 0.0рxр1.0 throughout the visible wavelength region. The dispersion, measured by a prism coupling waveguide technique, is found to be well described by a Sellmeier relation. Discrepancies among previous measurements of refractive index dispersion, as a consequence of different growth conditions and corresponding band gap bowing parameter, are reconciled when the Sellmeier relation is parameterized not by x but by band gap energy.

Three-dimensional ͑3-D͒ imaging is demonstrated using an electronically controlled liquid crystal ͑LC͒ optical lens to accomplish a no-moving-parts depth-section scanning in a modified commercial 3-D confocal microscope. Specifically, 3-D views of a standard CDC blood vessel ͑enclosed in a glass slide͒ have been obtained using the modified confocal microscope operating at the red 633-nm laser wavelength. The image sizes over a 25-m axial scan depth were 50ϫ 50 m and 80ϫ 80 m, using 60ϫ and 20ϫ micro-objectives, respectively. The transverse motion step was 0.1 m for the 60ϫ data and 0.2 m for the 20ϫ data. As a first-step comparison, image processing of the standard and LC electronic-lens microscope images indicates correlation values between 0.81 and 0.91. The proposed microscopy system within aberration limits has the potential to eliminate the mechanical forces due to sample or objective motion that can distort the original sample structure and lead to imaging errors.

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Surface plasmon polaritons propagating in a high dielectric contrast system are investigated numerically. Using frequency domain simulations, we show that a three layer system consisting of air–silicon (7nm)–silver supports two different modes at the Ag–Si interface: a fast mode, which exhibits normal dispersion, and a slow mode, which exhibits anomalous dispersion. Near the Ag–Si surface plasmon polariton resonance frequency, surface waves with a wavelength of 25nm are observed at a vacuum wavelength of 595nm, equivalent to λf∕24. The results show the possibility of exciting surface waves with extreme ultraviolet wavelengths using visible frequencies.

Frequency dependent near-field scanning optical microscopy (NSOM) measurements of plasmon-mediated near-field focusing using a 50nm thick Au film are presented. In these studies the tip aperture of a NSOM probe acts as a localized light source, while the near-field image formed by the metal lens is detected in situ using nanoscale scatterers placed in the image plane. By scanning the relative position of object and probe, the near-field image generated by the lens is resolved. NSOM scans performed at different illumination frequencies reveal an optimum near-field image quality at frequencies close to the surface plasmon resonance frequency.