Probing the potential applications of terahertz radiation in wood products

In the wood products industry, terahertz (THz) radiation is showing promise as a new remote sensing technology with many applications. The purpose of this project was to probe the interaction of terahertz radiation with wood to determine the extent of these possibilities. Three avenues of study were undertaken: 1. Probe the cylindrical structure of wood in a reflection geometry, 2. Study the birefringence of different species of oven dry wood, 3. Study the extinction coefficient of different species of oven dry wood. These three studies increased our understanding of the interaction between THz radiation and wood. Prior to this study, the extinction mechanism in THz transmission through wood was an open question. Three mechanisms were identified: absorption by the vibrational and rotational modes of the wood and water molecules scattering by the dielectric cylindrical wood cells and, diffraction by the earlywood-latewood pattern. This project determined that absorption by the wood and water molecules is the dominant extinction mechanism in transmission through wood, contributing to ~90% of the signal attenuation. --P. i.