Knowledge Bank

This paper will discuss the implications of spectral interference from atmospheric constituents on the performance of spectroscopic point sensors in the submillimeter/terahertz (SMM/THz) spectral range. Spectral 'clutter' can be a limiting factor for spectroscopic sensors, especially where high sensitivity and specificity are required. The most abundant atmospheric gases are either transparent or have spectra that are very sparse in the SMM/THz. For SMM/THz sensors that utilize continuous wave (cw) electronic techniques the clutter limit for the detection of common target gases is in the ppt (1 part in $1012$) or lower range. This warrants 'absolute' specificity of molecular identification with probability of false alarm well below $10-10$. Moreover, the low clutter limit demonstrated for cw electronic systems in the SMM/THz is independent of system size and complexity.