Browsing by Author "Wahaia, Faustino"

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    Effect of bone age and anatomy on the variability of the bovine bone by-product by Terahertz time-domain spectroscopy and energy-dispersive X-ray microanalysis
    (2024) Wahaia, Faustino; Kasalynas, Irmantas; Karaliunas, Mindaugas; Urbanowicz, Andrzej; Seifert, Birger; Valusis, Gintaras; Ferraro, Vincenza
    Bone is among the main by-products of the meat and dairy livestock. Currently, in many countries, it is valorised in pet food, disposed through incineration or exported. However, thanks to its biological and mechanical properties, it could be used in several bio-based products such as coatings, packaging, phosphorous, calcium and magnesium supply, flame retardants, etc. Successful valorisations routes of discarded bones need a comprehensive characterization of the bone tissue variability with major biological factors such as age of the animal and the anatomy of the bone itself. In this study, this variability was assessed through Terahertz time-domain spectroscopy and energy dispersive X-ray microanalysis. Bones optical properties (refractive index and absorption coefficient) and main minerals (calcium and phosphorous), were determined for adult cows' femurs and tibias, from the same breed and breeding system and in the age range 93-120 months. Clustering analysis was then carried out, by unsupervised statistical tools (Principal Component Analysis and Agglomerative Hierarchical Clustering). Results showed that the bones considered can be grouped in two classes, represented by each anatomy; besides, the anatomy was most significant than age. The refractive index increased with age and was higher for femur; the cluster of tibias was more homogeneous than femurs. The THz radiation showed to be a useful and non-destructive tool to assess bovine bones variability and also their optical properties. This radiation could be applied to the predict animal bone components (collagen and minerals) extractability so as to valorise each cluster according to its potential.
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    Multiple-reflections single-shot dispersion scan for fast ultrashort-pulse measurements
    (2024) Capdeville, Francisco; Villanueva, Fernando; Hidalgo Rojas, Diego Mauricio; Wahaia, Faustino; Wheatley, Robert; Wallentowitz, Sascha; Volkmann, Ulrich; Seifert, Birger
    A single-shot non-interferometric ultrashort-pulse measurement method based on the dispersion scan (d-scan) technique with a substantially extended time span for the pulses to be measured is presented. While single-shot d-scan is typically used for rather short femtosecond pulses, the presented multiple-reflections d-scan (MR d-scan) technique allows measurement of both short and long femtosecond pulses. Single-shot d-scan is currently limited to pulses with a maximum duration of 60 fs using a chromatic dispersion, i.e., a group delay dispersion (GDD) of 4400 fs2 at 840 nm provided by customized random nonlinear crystals. MR d-scan achieves a GDD of 31100 fs2 at 820 nm in this work, but can generally achieve an increase in GDD of up to two orders of magnitude. MR d-scan works with commonly available output couplers, does not rely on a homogeneous, precisely imaged beam profile and has an in-line configuration. As an example, long femtosecond double pulses are measured and reconstructed.
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    Optical properties of millimeter-size metal-organic framework single crystals using THz techniques
    (2025) Wahaia, Faustino; Kasalynas, Irmantas; Pashnev, Daniil; Valusis, Gintaras; Urbanowicz, Andrzej; Karaliunas, Mindaugas; Singh, Dinesh Pratap; Wallentowitz, Sascha; Seifert, Birger
    Metal-organic frameworks (MOFs) crystals are promising emerging materials for terahertz (THz) photonics i.e., for THz wave generation through difference frequency or optical rectification and electrooptic detection, including optical components for THz beam steering. The present work reports optical properties of three different non-centrosymmetric single MOF crystals, grown by an innovative solvo-thermal technique with tunable morphology, termed MOF [Zn(3-ptz)2]n (MIRO-101). THz time-domain spectroscopy (TTDS) in the range of 0.25 - 1.5 THz has been used for the measurement of the transfer function, H(w) of these MOF crystals. Through this experimental function Hexp(w), optical parameters such as refractive index, nMOF(w) and absorption coefficient, aMOF(w) have been calculated for the analysis of the optical properties of this crystal. The results indicate that this MOF crystal offers opportunities for long-term exploration of properties toward the creation of novel nonlinear THz photonics materials, as a THz radiation emitter via Different Frequency Generation (DFG) or Optical Rectification (OR) and Electro-optic (EO) detection via optical sampling, including for its use in optoelectronics, and materials science.