Invariant embedding technique for medium permittivity profile reconstruction using terahertz time-domain spectroscopy

Kirill I Zaytsev,Valeriy E Karasik,Irina N Fokina,Valentin I Alekhnovich

doi:10.1117/1.oe.52.6.068203

Kirill I Zaytsev, Valeriy E Karasik + Show 2 more

Open Access

https://doi.org/10.1117/1.oe.52.6.068203

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Abstract

Reconstructing the dielectric permittivity profile (depth dependence of sample dielectric permittivity) is an important inverse problem. We present a new method for permittivity profile reconstruction based on terahertz time-domain spectroscopy signal processing. Reconstruction is accomplished in two steps. First, the sample pulse function is reconstructed using sample time-domain reflection data. Low- and high-frequency noise filtering and the interpolation of the pulse function at low frequencies are then applied. Second, an invariant embedding technique is used to calculate the dielectric permittivity profile based on the sample pulse function. Samples with known permittivity profiles have been studied experimentally using this procedure in order to verify this algorithm. This algorithm is stable to additive Gaussian white noise as shown using mathematical modeling based on the finite-difference time-domain technique. Possible applications of this permittivity profile reconstruction technique are discussed.

Highlights

Terahertz (THz) radiation is located between the infrared and microwave regions of the electromagnetic spectrum, from about 0.1 to 10.0 THz
THz imaging and spectroscopy systems are used in the detection of concealed weapons, drugs, and explosives,[2,3] medical diagnostics,[4,5,6] and nondestructive evaluation of construction materials.[7,8]
The ability of THz time-domain spectroscopy (TDS) applied to media dielectric permittivity profile reconstruction was shown

Summary

Introduction

Terahertz (THz) radiation is located between the infrared and microwave regions of the electromagnetic spectrum, from about 0.1 to 10.0 THz. Because of these properties, there are many potential applications of THz technology.[1] For instance, THz imaging and spectroscopy systems are used in the detection of concealed weapons, drugs, and explosives,[2,3] medical diagnostics,[4,5,6] and nondestructive evaluation of construction materials.[7,8]. Time-domain data can be used to reconstruct the permittivity profile in a sample (i.e., the dependence of the sample dielectric permittivity on depth) This reconstruction method aids in the study of the internal structure of a sample, known as THz tomography or T-ray tomography.[9] THz tomography is expected to be useful in medical diagnosis, nondestructive evaluation of construction materials, inspection of art objects, and other applications. This paper describes a new way to solve this inverse problem

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