Terahertz dielectric characterisation of polymethacrylimide rigid foam: the perfect sheer plate?

Terahertz time-domain spectroscopy measurements have been performed to characterise polymethacrylimide rigid foam in the 0.1-2 THz range. The authors found remarkably low permittivity (~1.03) and dielectric loss tangent (<0.5%) for thicknesses ranging from 3 to 15 mm with weak frequency dependence, making this material very promising for THz applications.