The remote bonding configuration allows the application of FBG sensors in extreme environments. But as the length of the fiber increases the attenuation in the fiber becomes significant and the signal-to-noise ratio (SNR) is reduced. The amplitude of wave energy coupled in the fiber depends on the type and quality of the bond, the materials in contact as well as the attenuation of the wave in the fiber. In this paper, FBG sensors with different coatings are used and the amplitude of the wave coupled is studied in each of the cases. Four different material coatings including acrylate, polyimide, aluminium coated and PEEK-coated FBGs are used for the purpose.
In this work results on laser assisted formation of silver nanoparticles in glass are presented. The sample material used in the experiments is Ag doped borosilicate glass fabricated by conventional melt quenching method. The glass samples are irradiated by nanosecond laser pulses at wavelength of 266 nm with a wide range of fluences and number of applied pulses. It is found that the laser radiation can lead to specific yellow coloration of the irradiated areas. The performed analyses show formation of silver nanoparticles in these zones. The optical properties of the irradiated areas are found to depend on the laser processing parameters and the silver concentration. The mechanism of nanoparticle formation is also discussed. The presented method can be used for formation of nanoparticles inside transparent materials and can be used for fabrication of novel materials with application in photonics.
In this work laser-assisted methods for metal nanostructures formation and their application as active substrates in Surface Enhanced Raman Spectroscopy are presented. The nanostructures are fabricated by laser processing of gold thin films deposited on low cost substrates as glass, ceramic, polymer and paper. The films are deposited by classical PLD technology. The produced films are then processed by nanosecond pulses delivered by nanosecond Nd:YAG laser system. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. Femtosecond Pulsed Laser Deposition in air is also applied for direct deposition of gold nanostructure. In another set of experiments gold nanoparticle colloids are fabricated by laser ablation of gold target in chloroform. The fabricated structures are then tested as active systems in SERS, as detection of pesticides (DDT), nitrates (NH4NO3), and drugs (Methylene blue) is demonstrated. The obtained results show that these nanostructures can be efficiently used in the detection and monitoring of materials with a high social impact.
Pulsed Laser Deposition (PLD) technique is applied to produce organic semiconductor (OS) rubrene thin film for spintronics applications. The use of organic material for spintronics is motivated by the advantages such as long spin diffusion length due to low spin-orbit and hyperfine coupling1,2, chemical tuning of electronic functionality, easy structural modifications, ability of self-assembly and mechanical flexibility3 etc. However, a major drawback of OS is its low mobility compared to inorganic semiconductors. The PLD growth of rubrene aims on fabricating OS films under more controlled environment to achieve higher crystalline order to improve its mobility and spin coherence length. Among organic materials, rubrene reveals the highest hole mobility - up to 40 cm2/(V∙s) and can be exploited in organic light-emitting diodes (OLEDs) or field-effect transistors (OFETs) 4. In this work the rubrene thin films are produced from hardened pellets in vacuum using Nd:YAG pulsed laser operated at 1064 nm, 2 Hz and energy fluence around 0.2 J/cm2. For the reference rubrene samples on SiO2 glass the AFM data reveal continuous 5-7 nm thick films. The amorphous structures are confirmed by XRD measurements and also Raman spectra which show signatures of both tetracene and phenyl bands and a broadband at 1373 cm-1. The obtained results indicate that continuous, defect-free rubrene films can be prepared by means of PLD for investigation of the spin polarization properties of organic-inorganic hybrids. Further studies are on the way to improve crystalline qualities of the rubrene films for less grain boundary related defects and improved mobility and spin diffusion length.
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