Determination of the origin of birefringence in wood at terahertz frequencies

In the wood products industry, terahertz (THz) radiation is an emerging technology that is showing promise for new types of monitoring. These applications are dependent on the ability of THz radiation to probe the gross fibre structure of wood. The sensitivity to this gross fibre structure results from strong birefringence at THz frequencies. Prior to this thesis work, the nature of the birefringence exhibited in wood was an open question. Based on the physical structure of wood, the large birefringence observed can be due to intrinsic birefringence, resulting from the dielectric properties of the wood material present in the cell walls, or form birefringence, resulting from the repetitive array of cylindrical cells present in the wood structure. This thesis determines for the first time the origin of birefringence at THz frequencies in wood.