On-line calibration for linear time-base error correction of terahertz spectrometers with echo pulses

Abstract

We use a terahertz echo pulse as a transfer standard to correct linear time-base errors of a terahertz spectrometer. With this calibration technique, the linear error of the translate stage is corrected and the spectral repeatability of the spectrometer is improved. This calibration technique is able to correct each ‘shot’ of the terahertz pulse and can realize on-line calibration of the terahertz spectrum. The average of multiple measurements of carbon monoxide gas absorption lines was corrected and the deviation was reduced by a factor of 2.5 using this technique. This on-line calibration technique needs no additional optical components and causes no performance degradation of the terahertz spectrometer. It provides a simple and alternative method to the conventional interferometric technique and allows for accurate measurement of spectral properties of specimens in the terahertz region.