Detection and correction of the misplacement error in THz Spectroscopy by application of singly subtractive Kramers-Kronig relations

TL;DR

This paper presents a rigorous optimization method using singly subtractive Kramers-Kronig relations to detect and correct phase misplacement errors in THz reflection spectroscopy, improving the consistency of permittivity measurements.

Contribution

The paper introduces a novel application of singly subtractive Kramers-Kronig relations for correcting phase errors in THz spectroscopy data.

Findings

Effective correction of phase misplacement errors demonstrated on InAs wafer data.

Improved consistency between amplitude and phase measurements achieved.

Method applicable within the 0.5 to 2.5 THz spectral range.

Abstract

In THz reflection spectroscopy the complex permittivity of an opaque medium is determined on the basis of the amplitude and of the phase of the reflected wave. There is usually a problem of phase error due to misplacement of the reference sample. Such experimental error brings inconsistency between phase and amplitude invoked by the causality principle. We propose a rigorous method to solve this relevant experimental problem by using an optimization method based upon singly subtractive Kramers-Kronig relations. The applicability of the method is demonstrated for measured data on an n-type undoped (100) InAs wafer in the spectral range from 0.5 up to 2.5 THz.