W. CHARLES SYMONS and ROBERT A. LODDER, University of Kentucky, College of Engineering and College of Pharmacy, A123 ASTeCC, Lexington, KY 40506-0286, symons@engr.uky.edu and lodder@pop.uky.edu


The Near-Field Scanning Optical Microscope (NSOM) allows spectral imaging of samples beyond the diffraction limit of traditional optical microscopes. NSOM instruments achieve this type of resolution by raster scanning a subwavelength aperture within a wavelength distance of a sample. This ability further enhances current macroscopic and microscopic near-IR imaging capabilities. In preparation for imaging LDL and oxLDL receptors as they bind LDL and oxLDL, NSOM spectral images of polystyrene beads have been obtained utilizing wavelengths from 1700 nm to 1800 nm generated by a tunable laser diode source. Additionally, near-IR spectra of cholesterol have also been obtained utilizing the NSOM instrument. Furthermore, image data interpretation can be enhanced and expedited through greater understanding of the near-field effects on analyte particles as gathered through electromagnetic modeling of the NSOM instrument. Specifically, Moment Method, Finite-Difference Time Domain (FDTD), and Finite Element Method (FEM) techniques have all been utilized to simulate the electromagnetic scattering characteristics of metallic and dielectric samples within the near-field of a subwavelength aperture. To this end, simulated images have been generated using a massively parallel supercomputer, a Convex Exemplar SPP-2000, in order to better study such effects as incident wave polarization, aperture/sample separation distance, and aperture size.