Precision millimeter-wave measurements of complex refractive index, complex dielectric permittivity, and loss tangent of common polymers

Our improved dispersive Fourier transform technique applied to a polarizing two-beam interferometer enables us to provide high-precision continuous spectra of complex refractive index, complex dielectric permittivity, and loss tangent of polyethylene, polypropylene, poly-4 methyl pentene-1 (TPX), polytetrafluorethylene, Plexiglas, acrylic, and nylon over the frequency range 50–300 GHz. The first four are nonpolar polymers and exhibit extremely low-loss characteristics. The last three are typical polar polymers, but they exhibit nearly 20 to 30 times higher loss compared to nonpolar polymers.