Near-field optics imaging in silica waveguide using near-field scanning optical microscope

We investigated the near-field optics imaging by a numerical method using special spherical chains created in a silica waveguide (SWG) and explored the possibility of how this can be used for near-field scanning optical microscopy (NSOM) applications. There are two types of spherical nanochain; type A includes nano-dielectric spheres connected closely, and type B includes silver nanoparticles 4 nm in diameter randomly distributed inside the nanospheres of type A. A spherical nanochain with the 80-nm-diameter spheres was embedded in the SWG. The interactions between light emerging from SWG and the electric field near the sample surface that affects the properties of the images produced by NSOM are analyzed using a three dimensional finite-difference time-domain method. The effects of the optical field distribution generated by some factors are also discussed. A method of controlling the light field localized in the SWG is proposed that uses the external protrusion (dielectric sphere). The proposed structure will yield some useful information and give an idea of applications in NSOM. © 2007 The Japan Society of Applied Physics.