Interaction of spherical nanoparticles with a highly focused beam of light.

The interaction of a highly focused beam of light with spherical nanoparticles is investigated for linear and radial polarizations. An analytical solution is obtained to calculate this interaction. The Richards-Wolf theory is used to express the incident electric field near the focus of an aplanatic lens. The incident beam is expressed as an integral where the integrand is separated into transverse-electric (TE) and transverse-magnetic (TM) waves. The interaction of each TE and TM wave with a spherical nanoparticle is calculated using the Mie theory. The resulting analytical solution is then obtained by integrating the scattered waves over the entire angular spectrum. A finite element method solution is also obtained for comparison.

Focusing characteristics of a planar solid-immersion mirror.

The focusing characteristics of a planar waveguide solid-immersion mirror with parabolic design have been investigated. The solid-immersion mirror is integrated into an optical waveguide, and light focusing is achieved with a parabolic mirror parallel to the waveguide plane and waveguide mode confinement normal to the waveguide plane. Optical-quality tantala silica planar waveguides can be obtained by evaporation. The parabolic sidewall reflects over 50% of the incident waveguide mode and generates a diffraction-limited focus. The measured spot size for the solid-immersion mirror described here is less than one third of the wavelength. Polarization analysis shows that the electric field near the focal region has components parallel and normal to the polarization state of the incident beam. The planar solid-immersion mirror is essentially free of chromatic aberration, and the alignment of the illumination beam is within a fraction of degrees.

Near-field radiation from a ridge waveguide transducer in the vicinity of a solid immersion lens.

A near-field optical system is investigated to improve the transmission efficiency of near-field transducers. A ridge waveguide is placed adjacent to a solid immersion lens (SIL) but separated by a low-index dielectric layer. The incident electric field near the focus of the SIL is determined by the Richards-Wolf vector field equations. The finite element method is used to solve Maxwell's equations. A spot size of 31 nm is obtained. The maximum value of the absorbed optical power density in the recording medium is 7.51 x 10(-4) mW/nm3 for a 100 mW input power.

Miniature planar solid immersion mirror with focused spot less than a quarter wavelength.

We describe a microoptical planar waveguide solid immersion mirror with high optical throughput, and show that it can focus light to spot sizes of ~90 nm at a wavelength of 413 nm. Scanning near field optical microscope images of the light within the device are in good agreement with a simple theoretical model. This device is accurately mass-produced with lithographic and thin film deposition techniques known from modern integrated circuit processing.

Input-grating couplers for narrow Gaussian beam: influence of groove depth.

Input-grating coupling characteristics have been studied for narrow Gaussian beam incidence and finite-length grating coupler with an electromagnetic full-vector field model based on the finite-difference time domain (FDTD) method. Analytic analysis based on perturbation theory has been compared to the FDTD technique. The influences of the variation in grating period, modulation depth, corrugation, and beam size have been investigated. Certain aspects of the calculated results have been confirmed with experiments.