scholarly journals Attenuated Total Reflection at THz Wavelengths: Prospective Use of Total Internal Reflection and Polariscopy

2021 ◽  
Vol 11 (16) ◽  
pp. 7632
Author(s):  
Meguya Ryu ◽  
Soon Hock Ng ◽  
Vijayakumar Anand ◽  
Stefan Lundgaard ◽  
Jingwen Hu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Biological Samples ◽  
Total Internal Reflection ◽  
Refractive Index Change ◽  
High Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
Experimental Conditions ◽  
Frustrated Total Internal Reflection

Capabilities of the attenuated total reflection (ATR) at THz wavelengths for increased sub-surface depth characterisation of (bio-)materials are presented. The penetration depth of a THz evanescent wave in biological samples is dependent on the wavelength and temperature and can reach 0.1–0.5 mm depth, due to the strong refractive index change ∼0.4 of the ice-water transition; this is quite significant and important when studying biological samples. Technical challenges are discussed when using ATR for uneven, heterogeneous, high refractive index samples with the possibility of frustrated total internal reflection (a breakdown of the ATR reflection mode into transmission mode). Local field enhancements at the interface are discussed with numerical/analytical examples. Maxwell’s scaling is used to model the behaviour of absorber–scatterer inside the materials at the interface with the ATR prism for realistic complex refractive indices of bio-materials. The modality of ATR with a polarisation analysis is proposed, and its principle is illustrated, opening an invitation for its experimental validation. The sensitivity of the polarised ATR mode to the refractive index between the sample and ATR prism is numerically modelled and experimentally verified for background (air) spectra. The design principles of polarisation active optical elements and spectral filters are outlined. The results and proposed concepts are based on experimental conditions at the THz beamline of the Australian Synchrotron.

scholarly journals Attenuated Total Reflection at THz Wavelengths: Peculiarities of Total Internal Reflection and Polariscopy

2021 ◽  
Author(s):  
Meguya Ryu ◽  
Soon Hock Ng ◽  
Vijayakumar Anand ◽  
Stefan Lundgaard ◽  
Jingwen Hu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Biological Samples ◽  
Total Internal Reflection ◽  
Refractive Index Change ◽  
High Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
Optical Elements ◽  
Frustrated Total Internal Reflection

Capabilities of the Attenuated Total Reflection (ATR) at THz wavelengths for increased sub-surface depth characterisation of (bio-)materials is presented. The penetration depth of a THz evanescent wave in biological samples is dependent on the wavelength and temperature and can reach 0.1-0.5 mm depth due to strong refractive index change ∼0.4 of the ice-water transition; this is quite significant and important when studying biological samples. Technical challenges are discussed when using ATR for uneven, heterogeneous, high refractive index samples with possibility of frustrated total internal reflection (a breakdown of the ATR reflection-mode into transmission-mode). Local field enhancements at the interface are discussed with numerical/analytical examples. Maxwell’s scaling was used to model behaviour of absorber-scatterer inside materials at the interface with ATR prism for realistic complex refractive indices of bio-materials. Modality of ATR with polarisation analysis is proposed and its principle illustrated, opening an invitation for its experimental validation. The sensitivity of the polarised ATR mode to the refractive index between the sample and ATR prism is revealed. Design principles of polarisation active optical elements and spectral filters are outlined. The results and concepts are based on experiments carried out at the THz beamline of the Australian Synchrotron.

Comparison of sensitivity of the refractometric methods of frustrated total internal reflection and surface plasmon resonance

2020 ◽  
pp. 44-49
Author(s):  
I. N. Pavlov
Keyword(s):  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Total Internal Reflection ◽  
Resonance Method ◽  
Internal Reflection ◽  
Optical Methods ◽  
Thin Boundary Layer ◽  
Experimental Conditions ◽  
Frustrated Total Internal Reflection

Two optical methods, namely surface plasmon resonance imaging and frustrated total internal reflection, are described in the paper in terms of comparing their sensitivity to change of refractive index of a thin boundary layer of an investigated medium. It is shown that, despite the fact that the theoretically calculated sensitivity is higher for the frustrated total internal reflection method, and the fact that usually in practice the surface plasmon resonance method, on the contrary, is considered more sensitive, under the same experimental conditions both methods show a similar result.

scholarly journals Characterisation of Biological Materials at THz Frequencies by Attenuated Total Reflection: Lard

2020 ◽  
Vol 10 (23) ◽  
pp. 8692
Author(s):  
Zoltan Vilagosh ◽  
Alireza Lajevardipour ◽  
Dominique Appadoo ◽  
Soon Hock Ng ◽  
Saulius Juodkazis ◽  
...  
Keyword(s):  
Penetration Depth ◽  
Evanescent Wave ◽  
Total Internal Reflection ◽  
Complex Refractive Index ◽  
Biological Tissues ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Frustrated Total Internal Reflection ◽  
Model Sample ◽  
Difference Time

The penetration depth of an evanescent wave in Attenuated Total Reflection (ATR) is dependent on the wavelength of the radiation utilised. At THz frequencies, the penetration depth into biological tissues is in the order of 0.1 to 0.5 mm; rendered pig lard was used as a model sample in this study. A method for the direct measurement of the evanescent wave penetration depth is presented which allows for the estimation of the dispersion of the complex refractive index by using the reflection of the evanescent wave from varying sample depths. The method employs frustrated total internal reflection, and has been demonstrated by using the THz/Far-IR beamline at the Australian synchrotron, and modelled using finite difference time domain (FDTD) simulations.

scholarly journals Extraction of light trapped due to total internal reflection using porous high refractive index nanoparticle films

Nanoscale ◽  
2014 ◽  
Vol 6 (14) ◽  
pp. 8177-8184 ◽  
Author(s):  
Peng Mao ◽  
Fangfang Sun ◽  
Hanchao Yao ◽  
Jing Chen ◽  
Bo Zhao ◽  
...  
Keyword(s):  
Refractive Index ◽  
Gas Phase ◽  
Total Internal Reflection ◽  
High Refractive Index ◽  
Internal Reflection ◽  
Cluster Beam ◽  
Nanoparticle Films ◽  
Phase Cluster ◽  
Cluster Beam Deposition ◽  
Beam Deposition

Porous TiO2nanoparticle layers are fabricated by gas phase cluster beam deposition at glancing incidence.

Novel Attenuated Total Reflection Fourier Transform Infrared Microscopy Using a Gem Quality Diamond as an Internal Reflection Element

2005 ◽  
Vol 59 (10) ◽  
pp. 1236-1241 ◽  
Author(s):  
Sanong Ekgasit ◽  
Pimthong Thongnopkun
Keyword(s):  
Fourier Transform ◽  
Total Internal Reflection ◽  
Fourier Transform Infrared ◽  
Normal Incidence ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
The Novel ◽  
Infrared Microscope ◽  
Ft Ir

A novel technique for attenuated total reflection Fourier transform infrared (ATR FT-IR) spectral acquisition by an infrared microscope with a gem-quality faceted diamond as an internal reflection element (IRE) is introduced. Unlike conventional IREs, the novel diamond IRE has a sharp tip configuration instead of a flat tip configuration. Light at normal incidence was coupled into the diamond while the transflected radiation from the diamond was collected through the table facet by the built-in 15× Cassegrainian objective. The number of reflections in the novel diamond IRE equals two. The evanescent field generated under total internal reflection at the pavilion facet was exploited for ATR spectral acquisition of materials attached to the IRE. The observed ATR spectra were compared to those obtained via a traditional zinc selenide IRE.

TYPE-II SUPERLATTICES AND VARIABLE OVERLAP SUPERLATTICES IN TOTAL INTERNAL REFLECTION SWITCHES FOR THE LONGWAVE INFRARED

1993 ◽  
Vol 02 (03) ◽  
pp. 415-436 ◽  
Author(s):  
E.R. YOUNGDALE ◽  
J.R. MEYER ◽  
C.A. HOFFMAN ◽  
F.J. BARTOLI ◽  
W.I. WANG
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Total Internal Reflection ◽  
Optical Switching ◽  
Refractive Index Change ◽  
Realistic Model ◽  
Internal Reflection ◽  
Type Ii ◽  
Index Change ◽  
Type Ii Superlattices

We derive explicit criteria for the properties required of a semiconductor nonlinear medium suitable for use in all-optical switching devices employing total internal reflection. Transmission as a function of laser intensity and film thickness has been calculated using a realistic model for penetration of the evanescent beam under TIR conditions. Requirements based on these results include a large nonlinear refractive index, large index change at saturation and small absorption coefficient. We show that unlike previously-studied semimetals and narrow-gap semiconductors, Type-II superlattices such as InAs-GaSb and variable-overlap superlattices (variants of Type-II which include a spacer between the layer containing the conduction-band minimum and that containing the valence band maximum) such as InAs-AlSb-GaSb hold prospects for satisfying all of these requirements simultaneously. As the free carrier lifetime will have a crucial influence on device performance, we have initiated a systematic experimental study of electron-hole recombination in InAs-based superlattices. From degenerate and nondegenerate four-wave mixing experiments, we have also determined nonlinear optical coefficients as a function of difference frequency and intensity. An InAs-GaSb superlattice has been found to display a refractive index change of ≈ 0.1, as well as device figures of merit which slightly surpasses any previously reported for weakly-saturating nonlinearities at CO 2 wavelengths. It is anticipated that future experiments on Type-II superlattices with longer lifetimes may yield nearly two orders of magnitude additional improvement in the nonlinear refractive index.

Attenuated (but Not Total) Internal Reflection FT-IR Spectroscopy of Thin Films

2002 ◽  
Vol 56 (5) ◽  
pp. 665-669 ◽  
Author(s):  
Will Cantrell ◽  
George E. Ewing
Keyword(s):  
Theoretical Basis ◽  
Total Internal Reflection ◽  
Spectroscopic Technique ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
Geometric Constraints ◽  
Ft Ir ◽  
Atr Spectroscopy ◽  
Ft Ir Spectroscopy

We present a spectroscopic technique that is a hybrid between reflection-absorption and attenuated total reflection (ATR) spectroscopy. The method, which we call attenuated internal reflection (AIR), is suitable for the investigation of thin film liquids on non-or weakly absorbing substrates. In AIR the interrogating infrared beam is not exposed to vapor that may be associated with the film, but unlike ATR there are few geometric constraints on the substrate. We show the theoretical basis for the method and results from experiments demonstrating its use.

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