Measurement of Terahertz Attenuation using a Photo-Acoustic Substitution Method

We have developed a method for measuring terahertz (THz) attenuation for free-space beams. It employs a photo-acoustic detector to compare THz attenuation to audio frequency (AF) attenuation. The AF attenuation at 1 kHz is obtained directly by comparison with an inductive voltage divider as a reference standard. Using a metalized-film attenuator, we have demonstrated attenuation measurements up to 20 dB for 0.11 THz collimated beams generated by a Gunn oscillator using a corrugated horn antenna and an off-axis parabolic mirror.