Abstract
One of the key elements of terahertz time-domain spectrometers is the optical delay line. Usually it consists of a motorized translation stage and a corner reflector mounted on its top. Errors in the positioning of the translation stage lead to various distortions of the measured waveform of terahertz pulses and, therefore, terahertz spectra. In this paper, the accuracy of position measurements is improved by using an optical encoder. Three types of systematic errors are found: Increasing and periodic offsets of the translation stage position, as well as a drift of its initial position in a series of consecutive measurements. The influence of the detected errors on the measured terahertz spectra is studied and correction methods are proposed.
Highlights
Terahertz time-domain spectroscopy (THz-TDS) has become one of the most common methods for studying optical and dielectric properties of materials in the frequency range of 0.1–10 THz with the development of femtosecond laser technology [1,2]
We propose a simple and cost-effective method to improve the accuracy of optical delay line positioning by using an optical encoder
To study the random and systematic errors of the optical delay line and the effect of these errors on the measured terahertz spectra, experiments were carried out on a THz spectrometer created in the Institute of Automation and Electrometry of Siberian Branch of Russian Academy of Sciences
Summary
Terahertz time-domain spectroscopy (THz-TDS) has become one of the most common methods for studying optical and dielectric properties of materials in the frequency range of 0.1–10 THz with the development of femtosecond laser technology [1,2]. This method is used to study nonlinear optical crystals [3,4], nuclear spin isomers [5], complex biomolecules [6], and charge carriers in solids [7,8]. An optical delay line allows changing of the path difference between generation and detection optical channels of the spectrometer This enables point-by-point sampling of the terahertz pulse waveform.
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