1,721,136 research outputs found
Analisi mediante spettroscopia micro-Raman di pigmenti ritrovati in frammenti di ceramiche comuni dai contesti protostorici e romani del santuario
No full textInfluence of composition on the electro-optic coefficients of Mg-doped lithium niobate
No full textthe EO coefficients r33, r13 and rc of Magnesium doped Lithium Niobate crystals are measured in the wavelength range 532-1550 nm and compared to the ones of pure congruent and stoichiometric Lithium Niobate. Magnesium is among the most effective doping ions for improving the photorefractive damage resistance of Lithium Niobate. The exploitation of the outstanding EO properties of Magnesium doped Lithium Niobate at high power levels are foreseen
Structural investigation of high-Tc superconductor EuBa2Cu3Oy by microRaman spectroscopy
No full textPolycrystalline EuBa2Cu3Oy (EuBCO) samples with various oxygen contents (y 6.25, 6.38 and 6.8) have been analysed by
means of microRaman spectroscopy. The usual Raman features of REBa2Cu3Oy high temperature superconductors (RE Y,
Eu, Sm, Er1⁄4) have been con®rmed also for EuBCO. A correlation between the crystal structure and the conductivity properties
as a function of the oxygen content has been established by studying in detail the features of the different Raman spectra. In
particular, the analysis of the peak pro®les of lattice vibrations involving oxygen atoms provides important information to
understand the anomalous superconducting properties found in the sample with y 6.38. In addition, the appearance in the
superconducting samples of a new mode centred at 223 cm21 may be correlated to ordering phenomena which have been called to justify the conductivity results
Nuove metodologie per le Scienze Forensi: la spettroscopia Raman nella rilevazione di tracce ematiche
No full textLe attività nell’ambito delle Scienze forensi dell’Università di Pavia sono state oggetto di un Workshop internazionale dal titolo “Improving the death scene investigation: advanced multidisciplinary approaches and their use in court” con la partecipazione del Direttore del Servizio di Polizia Scientifica e dei Direttori dei Reparti Speciali della Polizia di Stato e del Comandante del Racis che è stata espressione dell’importanza dell’approccio interdisciplinare alle tematiche forensi e della consolidata collaborazione tra i differenti attori. In tal senso va sottolineata la nascita di una piattaforma universitaria interdipartimentale che si occupa di Scienze Forensi (FIND – Forensic Interdisciplinary Networking Domain) aperta al contributo di molti attori esterni.
Alla base di questo progetto vi è la condivisa convinzione che l’unico modo di rendere le investigazioni scientifiche davvero probanti ai fini giudiziali sia la continua collaborazione tra enti differenti e tra professionalità differenti, ciascuna al servizio di un fine comune, non raggiungibile se perseguito individualmente come peraltro evidenziato a proposito della spettroscopia micro-Raman.
In aggiunta ai risultati mostrati nell’articolo si riporta nel seguito un interessante risultato che indica come la tecnica possa diventare valido strumento complementare alla classica prova del Luminol. L’analisi micro-Raman è stata condotta su di un’ascia arrugginita che presentava alcune macchie apparentemente attribuibili a materiale ematico. In tal caso l’analisi al Luminol porterebbe a risultati non affidabili poiché notoriamente la presenza di ruggine, ossido di Ferro α-Fe2O3, produce un cosidetto falso positivo al Luminol, cioè la reazione luminescente viene attivata non dalla presenza di materiale ematico ma dalla ruggine stessa. In questo la spettroscopia micro-Raman consente di discriminare molto rapidamente la differente natura di tracce a composizione differente come è facile notare dagli spettri riportati nella figura sottostante e prevelati da due zone differenti come mostrato dalle frecc
ROLE OF INTRINSIC AND EXTRINSIC DEFECTS IN THE ELECTRO-OPTIC RESPONSE OF MAGNESIUM DOPED LITHIUM NIOBATE
No full textThe electro-optic coefficients r33, r13 and rc of congruent and stoichiometric magnesium doped lithium niobate are measured via interferometry and polarimetry in a wide wavelength range. An investigation via Raman spectroscopy is performed for a deeper understanding of the observed features
GRATING DIRECT INSCRIPTION IN LITHIUM NIOBATE THROUGH NEAR-INFRARED FEMTOSECOND LASER PULSES
No full textMicrometer-pitch surface and embedded gratings were inscripted in lithium niobate through multiphoton absorption excited via focussed femtosecond laser pulses. The drawbacks and the points of strength of the investigated line-by-line grating writing technique are discussed and compared to two beam interference. To the best of our knowledge, it is the first report of embedded gratings in Lithium Niobate
Microstructural modification of LiNbO3 crystals induced by femtosecond laser irradiation
No full textMicrostructural modifications were induced by femtosecond laser irradiation on lithium mobate (LN) crystals and investigated by means of optical microscopy and micro-Raman spectroscopy. Commercial z-cut congruent LN substrates were irradiated with focused ultra-short laser pulses at 810 nm, generated by a Ti:Sapphire oscillator or an amplified Ti:Sapphire laser system.
At the focus region, either refractive index changes or material removal were observed by varying the irradiation conditions. The Raman spectrum shows in the illuminated regions the insurgence of Raman modes, which are forbidden in the used-scattering geometry. This phenomenon increases gradually by approaching the ablation region, where nobium oxides and Li-deficient surfaces are formed for the low energy and high repetition rate pulses from the Ti:Sapphire oscillator. Amorphous surfaces are obtained for high energy and low repetition rate pulses from the amplified Ti:Sapphire laser system. (c) 2005 Elsevier B.V. All rights reserved
Optical and structural modification induced in LiNbO3 by femtosecond laser irradiation
No full textMicrometer-size structural modifications are induced in Lithium Niobate through femtoseconod laser irradiation and analysed by mean of confocal Raman spectroscop
Femtosecond Laser Writing of Surface Microstructures in Lithium Niobate
No full textFemtosecond pulses from an amplified Ti:Sapphire laser were found to be a surgically precise manufacturing tool for the formation of microstructures in Lithium Niobate crystals. Surface gratings were formed with 10% first order diffraction efficiency
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