CAP - Indexed Articles in Journals

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Browsing CAP - Indexed Articles in Journals by Author "7222"
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    Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Micromachining through Thermal Annealing
    ( 2019) Carlos Duarte Viveiros ; José Almeida ; Luís Carlos Coelho ; Helena Soares Vasconcelos ; Vítor Oliveira Amorim ; João Miguel Maia ; Pedro Jorge ; 3565 ; 5256 ; 5799 ; 5872 ; 6407 ; 6596 ; 7222
    A femtosecond laser direct writing system was developed to explore the fabrication of long-period fiber gratings (LPFGs) in SMF28 fibers. The LPFGs, showing the mode LP1,6 at 1500 nm, were exposed to high-temperature annealing up to 950 °C. Modifications in the refractive index (RI) modulation are observed through a blue-shift in the LPFG attenuation bands and above 850 °C, the mode LP1,7 appear at 1600 nm. The wavelength sensitivity to external RI from 1.300 to 1.452 was estimated for both modes before and after annealing. Greater sensitivity was found for the higher order mode in the entire range reaching 2400 nm/RIU around 1.440.
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    Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing
    ( 2020) Carlos Duarte Viveiros ; José Almeida ; Luís Carlos Coelho ; Helena Soares Vasconcelos ; João Miguel Maia ; Vítor Oliveira Amorim ; Pedro Jorge ; Paulo Vicente Marques ; 3565 ; 4287 ; 5256 ; 5799 ; 5872 ; 6407 ; 6596 ; 7222
    Long period fiber gratings (LPFGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond (fs) laser direct writing. LPFGs with longer and shorter periods were fabricated, which allows coupling from the fundamental core mode to lower and higher order asymmetric cladding modes (LP1,6 and LP1,12, respectively). For the grating periods of 182.7 and 192.5 µm, it was verified that the LP1,12 mode exhibits a TAP at approximately 1380 and 1448 nm in air and water, respectively. Characterization of the LPFGs subjected to high-temperature thermal treatment was accomplished. Fine-tuning of the resonance band’s position and thermal stability up to 600 °C was shown. The temperature sensitivity was characterized for the gratings with different periods and for different temperature ranges. A maximum sensitivity of -180.73, and 179.29 pm/°C was obtained for the two resonances of the 182.7 µm TAP LPFG, in the range between 250 and 600 °C.