Performance Comparison of Time-Domain Terahertz, Multi-terahertz, and Fourier Transform Infrared Spectroscopies

摘要

Time-domain terahertz (THz), multi-terahertz, and Fourier transform infrared (FTIR) spectroscopies access partly similar and partly complementary spectral ranges of the far-infrared region. We introduce an approach enabling a direct comparison of their performance in terms of the signal-to-noise ratio (SNR) and dynamic range (DR), normalized by the time required to obtain one useful data point in the frequency domain. Several configurations of a commercial FTIR spectrometer are compared to our various custom-built time-domain systems (including femtosecond oscillator and amplifier-based THz and multi-THz setups). We find that the normalized SNR of the FTIR systems is generally better than that of the time-domain setups, which is attributed to the noise of the femtosecond laser output compared to the black body radiation source. On the other hand, the coherent detection of the THz field in the time-domain systems leads to a dramatically better normalized DR than in the FTIR configurations.