AVS 47th International Symposium
    Processing at the Nanoscale/NANO 6 Thursday Sessions
       Session NS+NANO6+MC-ThA

Paper NS+NANO6+MC-ThA5
Dual-Wavelength Scanning Near-Field Optical Microscopy

Thursday, October 5, 2000, 3:20 pm, Room 302

Session: Near-field Optics and Photonics
Presenter: P.R. LeBlanc, McGill University, Canada
Authors: P.R. LeBlanc, McGill University, Canada
M. Gu, McGill University, Canada
P. Grutter, McGill University, Canada
D.G. Gray, McGill University, Canada
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We have developed a Dual-Wavelength Scanning Near-Field Optical Microscope to shed light onto the scanning process and investigate biological samples in air. We couple 442 and 325 nanometer light into a tapered optical fiber glued to a quartz tuning fork which serves as our `shear-force' sensor. Light transmitted through the sample is detected in a confocal arrangement by two photomultipliers. We have achieved topographical and optical resolutions of 10 and 30 nanometers, respectively. The dual-wavelength nature of our microscope permits the discrimination of topographical and optical cross-talk. It also allows the distinction of far-field artifacts from near-field features. Our primary biological application of the microscopy focuses on the investigation of the lignin distribution in wood fibers. Lignin, a cross-linked phenolic polymer, is of paramount importance in the pulp and paper-making processes. Our instrument permits the discrimination between chemical species density and topographical variations of the sample. The ratio of the two wavelength channels provides a simple and accurate parameter to determine the local concentration of lignin. These studies agree with atomic force microscopy images of wood cells and ultraviolet studies of wood cell walls.