scholarly journals Terahertz Time-Domain Polarimetry in Reflection for Film Characterization

Sensors ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 3352
Author(s):  
Sandrine van Frank ◽  
Elisabeth Leiss-Holzinger ◽  
Michael Pfleger ◽  
Christian Rankl
Keyword(s):  
Optical Properties ◽  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Single Layer ◽  
Measured Signal ◽  
Terahertz Time Domain Spectroscopy ◽  
Wide Range ◽  
Reflection Geometry ◽  
Layer Thin Film ◽  
Good Agreement

Terahertz time-domain spectroscopy is a useful technique to characterize layered samples and thin films. It gives access to their optical properties and thickness. Such measurements are done in transmission, which requires access to the sample from opposite sides. In reality this is not always possible. In such cases, reflection measurements are the only option, but they are more difficult to implement. Here we propose a method to characterize films in reflection geometry using a polarimetric approach based on the identification of Brewster angle and modeling of the measured signal to extract the refractive index and thickness of the sample. The technique is demonstrated experimentally on an unsupported single layer thin film sample. The extracted optical properties and thickness were in good agreement with established transmission terahertz spectroscopy measurements. The new method has the potential to cover a wide range of applications, both for research and industrial purposes.

scholarly journals Flow cell to study crystallisation processes in-situ using terahertz time-domain spectroscopy

2021 ◽  
Author(s):  
Qi Li ◽  
Johanna Kölbel ◽  
Terry Threlfall ◽  
Axel Zeitler
Keyword(s):  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Relaxation Dynamics ◽  
Terahertz Time Domain Spectroscopy ◽  
Great Opportunity ◽  
Time Domain Spectroscopy ◽  
Wide Range ◽  
Crystallisation Process ◽  
Static Conditions

A versatile setup based on terahertz time-domain spectroscopy was developed to monitor the process of crystallisation and characterise the structure of the crystals as well as the dynamics of the solvent in situ. The setup can be used to investigate crystallisation processes over a wide range of temperature, either under static conditions or during continuous flow. An attached optical imaging probe can be used to monitor the process in parallel to the terahertz spectroscopy investigation. The implementation of terahertz spectroscopy offers a great opportunity to investigate the dielectric relaxation dynamics of the solvent and the vibrational modes characteristic for the crystalline phases simultaneously. The details of the crystallisation setup are demonstrated at the example of the crystallisation process of magnesium sulphate heptahydrate from its aqueous phase.

Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Complex Refractive Index ◽  
Single Layer ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Wide Range ◽  
Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

Determination of pesticides in a flour substrate by chemometric methods using terahertz spectroscopy

2018 ◽  
Vol 10 (42) ◽  
pp. 5097-5104 ◽  
Author(s):  
Binghua Cao ◽  
Hui Li ◽  
Mengbao Fan ◽  
Wei Wang ◽  
Mengyun Wang
Keyword(s):  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Chemometric Methods ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy

Terahertz time-domain spectroscopy combined with chemometrics is utilized to identify imidacloprid and carbendazim in a flour substrate.

Soot Optical Properties in the Terahertz Spectra Domain

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Fei Wang ◽  
Ting Xu ◽  
Zhishen Qiang ◽  
Qunxing Huang ◽  
Dong Liu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Time Domain ◽  
Wavelength Region ◽  
Optical Methods ◽  
Optical Data ◽  
Refractive Indices ◽  
Spectroscopy Technique ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Combustion Diagnostics

For understanding and accurately modeling combustion, the important questions are what species are present in the flame, and the spatial distribution and temperature of these species. Traditional optical methods used only the electromagnetic waves in the wavelength region from the ultraviolet region up to the infrared. Terahertz time-domain spectroscopy technique can be used for the combustion research as a novel tool. However, for some sooty combustion environments, the strong absorption, spectral interference from soot scattering, and fluorescence from large molecules must be considered. The optical properties of soot in the terahertz domain are the main basic data for terahertz application. In this paper, the terahertz time-domain spectroscopy technique was used to study the optical properties of flame soot within 0.2–1.6 THz. The complex refractive indices of the soot were deduced by the fixed-point iteration method. In order to validate the results, the complex refractive indices of the soot from the four different fuel flames were deduced. It was found that the complex refractive indices in the terahertz domain of the soot from the different fuel flames are very close to each other. The comparisons of complex refractive indices between the visible–IR domain and the terahertz domain indicate that the value of absorption index in terahertz domain is smaller than in IR domain, which implies that the terahertz wave will penetrate the sooty flame with smaller absorption than the IR rays. The results can provide the basic optical data of flame soot for the application of terahertz time-domain spectroscopy technique in the optical combustion diagnostics and extend the optical combustion diagnostics application area.

Spectral characteristic of single layer graphene via terahertz time domain spectroscopy

Optik ◽  
2015 ◽  
Vol 126 (14) ◽  
pp. 1362-1365 ◽  
Author(s):  
Hong Cui ◽  
XianBin Zhang ◽  
Peng Yang ◽  
JunFei Su ◽  
XuYan Wei ◽  
...  
Keyword(s):  
Spectral Characteristic ◽  
Time Domain ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Layer Graphene

Investigation on Optical Properties of Transparent ITO Thin Films

2011 ◽  
Vol 347-353 ◽  
pp. 3481-3484
Author(s):  
Xue Hua Li ◽  
Dong Sheng Wang ◽  
Jian Zhou Du
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Refractive Index ◽  
Optical Properties ◽  
Glass Substrate ◽  
Film Theory ◽  
Single Layer ◽  
Minimum Value ◽  
Ito Thin Films ◽  
Layer Thin Film

Based on the single-layer thin film theory, we calculated transmittance of ITO thin film. The reflectivity arrive a maximum or a minimum according to whether the refractive index of film is greater or smaller than the refractive index of the glass substrate. we obtain the same maximum of transparence which is above 95% and the minimum value which decrease to 76.5% with the increase of refractive index.

scholarly journals Fiber Coupled Transceiver with 6.5 THz Bandwidth for Terahertz Time-Domain Spectroscopy in Reflection Geometry

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2616 ◽  
Author(s):  
Robert B. Kohlhaas ◽  
Lars Liebermeister ◽  
Steffen Breuer ◽  
Marcel Amberg ◽  
David de Felipe ◽  
...  
Keyword(s):  
Time Domain ◽  
Molecular Beam ◽  
Dynamic Range ◽  
High Mobility ◽  
Thz Imaging ◽  
Terahertz Time Domain Spectroscopy ◽  
Monolithically Integrated ◽  
Sensing Applications ◽  
Reflection Geometry ◽  
Thz Sensing

We present a fiber coupled transceiver head for terahertz (THz) time-domain reflection measurements. The monolithically integrated transceiver chip is based on iron (Fe) doped In0.53Ga0.47As (InGaAs:Fe) grown by molecular beam epitaxy. Due to its ultrashort electron lifetime and high mobility, InGaAs:Fe is very well suited as both THz emitter and receiver. A record THz bandwidth of 6.5 THz and a peak dynamic range of up to 75 dB are achieved. In addition, we present THz imaging in reflection geometry with a spatial resolution as good as 130 µm. Hence, this THz transceiver is a promising device for industrial THz sensing applications.

Application of Terahertz Spectroscopy and Imaging

2010 ◽  
Vol 5 (4) ◽  
pp. 123-129
Author(s):  
Mu Kaijun ◽  
Zhang Cunlin
Keyword(s):  
Time Domain ◽  
Quartz Crystal ◽  
Terahertz Spectroscopy ◽  
Thz Radiation ◽  
Radiation Polarization ◽  
Air Plasma ◽  
Thz Imaging ◽  
Terahertz Time Domain Spectroscopy ◽  
Security Applications ◽  
Angle Of Rotation

We examined the feasibility of Terahertz time-domain spectroscopy (THz-TDS) using a 4-mm-thick quartz crystal to extract the angle of rotation of THz radiation polarization induced by a two-color laser in air plasma. We also used the THz-TDS technique to identify explosives and melamine in mixtures. In addition, we presented a new opto-mechanical scanner for security applications using the method of passive THz imaging

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