Influence of OH-group concentration on optical properties of silica glass in terahertz frequency region

Tsuzuki, Seiji; Kuzuu, Nobu; Horikoshi, Hideharu; Saito, Katsuya; Yamamoto, Kohji; Tani, Masahiko

doi:10.7567/apex.8.072402

Cited by 16 publications

(8 citation statements)

References 18 publications

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“…A monotonic increase of the absorption is typically observed in amorphous solids [23] and biological macromolecular complexes formed by H -bond networks [19]. These absorption spectra can be generally approximated by a function C· ω β where C is a numerical coefficient which is expected to be proportional to the density of H -bonds, and β is an exponent which is approximately 2 in glassy materials [23,26]. A similar behavior to that described for biosystems rich in H -bonds is then expected also for cellulose where disordered H -bond networks are present.…”

Section: Resultsmentioning

confidence: 99%

Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

et al. 2017

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Artifacts made of cellulose, such as ancient documents, pose a significant experimental challenge in the THz transmission spectra interpretation due to their small optical thickness. In this Letter we describe a method to recover the complex refractive index of cellulose fibers from the THz transmission data obtained on single freely standing paper sheets in the 0.2-3.5 THz range. By using our technique, we were able to eliminate Fabry-Perot effects and recover the absorption coefficient of the cellulose fibers. The obtained THz absorption spectra are explained in terms of absorption peaks of the cellulose crystalline phase superimposed to a background contribution due to a disordered hydrogen bonds network. The comparison between the experimental spectra with THz vibrational properties simulated by density functional theory calculations confirms this interpretation. In addition, evident changes in the THz absorption spectra are produced by natural and artificial aging on paper samples, whose final stage is characterized by a spectral profile with only two peaks at about 2.1 THz and 3.1 THz. These results could be used to provide a quantitative assessment of the state of preservation of cellulose artifacts.

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Section: Resultsmentioning

confidence: 99%

Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

et al. 2017

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“…where C is a numerical coefficient which is expected to be proportional to the density of H bonds, β is an exponent which is approximately 2 in glassy materials and A is a constant [42]. In a previous work, the non-vanishing values of the constant A were interpreted as due to the existence of residual water in the paper structure [20].…”

Section: Resultsmentioning

confidence: 99%

Quantitative diagnostics of ancient paper using THz time-domain spectroscopy

Missori

Pawcenis

Bagniuk

et al. 2018

Microchemical Journal

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In this work we have studied the terahertz spectra of modern artificially aged and ancient paper samples using terahertz time-domain spectroscopy. Hydrothermal artificial ageing was performed in closed and open reactors. Ancient paper samples were produced during the 15 th century in European countries. The main aim of the work is the quantitative assessment of spectral feature observed by terahertz spectroscopy as a function of degradation. To this goal, the state of degradation of paper samples was characterized by crystallinity measurements obtained by using X-ray diffraction and by the degree of polymerization of cellulose polymers obtained by size exclusion chromatography. The behavior of the terahertz spectra was formerly investigated as a function of the hydration of paper samples. This allowed discriminating between the spectral features induced by the presence of water and those induced by degradation of paper. Results indicate clear dependences of spectral parameters from the evolution of crystallinity and the degree of polymerization. They can be used as a nondestructive analytical method to assess the state of degradation of ancient paper by terahertz spectroscopy.

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“…The waveguide was obtained by removing the cladding of a commercially available multi-mode optical fiber. The low OH content silica glass has a relative low material absorption (≈ 0.2 cm −1 ), and a nearly constant refractive index of 1.96 in the frequency range from 0.3 THz to 1 THz [26]. Due to the sub-wavelength cross-section of the waveguide higher order modes are not supported (the calculated V parameter at 635 GHz is 2.2 [27]), and the fundamental mode has a substantial evanescent field.…”

Section: Methodsmentioning

confidence: 99%

Ultra-high Q terahertz whispering-gallery modes in a silicon resonator

Vogt

Leonhardt

2018

APL Photonics

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We report on the first experimental demonstration of terahertz (THz) whispering-gallery modes (WGMs) with an ultra high quality (Q) factor of 1.5 × 10 4 at 0.62 THz. The WGMs are observed in a high resistivity float zone silicon (HRFZ-Si) spherical resonator coupled to a sub-wavelength silica waveguide. A detailed analysis of the coherent continuous wave (CW) THz spectroscopy measurements combined with a numerical model based on Mie-Debye-Aden-Kerker (MDAK) theory allows to unambiguously identify the observed higher order radial THz WGMs.

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Influence of OH-group concentration on optical properties of silica glass in terahertz frequency region

Cited by 16 publications

References 18 publications

Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

Quantitative diagnostics of ancient paper using THz time-domain spectroscopy

Ultra-high Q terahertz whispering-gallery modes in a silicon resonator

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