A high-pass filter system for measuring the spectrum of low-repetition rate or single pulse THz sources

We designed and manufactured terahertz (THz) waveguide high-pass filters (HPFs) with cutoff frequencies exceeding those of known analogs. These HPFs will be used in a proposed system for measuring spectra of single THz pulses or of the pulses radiated with a low-repetition rate. The system restores the pulse spectrum from measured amplitudes of the initial pulse and of the pulses, transmitted through HPFs with different cutoff frequencies. The system was simulated and showed to be applicable and effective for the pulses with durations exceeding 10 −9 s if developed HPFs with cutoff frequencies over 0.65 THz were used. The relative simulation error of determining the central frequency was equal to 2·10 −6 for THz pulse durations of 10 −5 s and longer.