Metasurface-Based Anti-Alias Filters for Improved THz-TDS Measurements

We propose an approach to improve the accuracy and speed of THz-TDS measurements in the low-frequency regime. It is based on applying anti-alias filters to narrow the frequency band of the THz signal that allows increasing the sampling interval in accordance with the Nyquist-Shannon theorem. The concept was verified by studying the transmittance spectra of the reference samples - band-pass THz filters centered at 156 and 376 GHz. We show a reduction of the spectrometer scanning time by an order of magnitude and an increase in measurement accuracy due to eliminating a long-term signal drift.