Diffraction effects in highly defocused THz beams

Terahertz communication links will require the use of directional beams to compensate for the higher losses compared to those faced in the few gigahertz region. The shorter wavelengths of terahertz waves also imply less diffraction from objects that may be present in many scenarios, such as books, bottles of water, or people. We present measurements of the frequency-dependent transmission losses for moderately divergent beams, with beam waists in the range of tens of centimeters, interacting with blockages. We compare our measurements with a quasi-optical treatment of these interactions based on the Fresnel diffraction theory. These results will inform the development of future generations of ultra-broadband communication technologies operating above 100 GHz.