1,720,982 research outputs found
Ultra-short wavelength operation of a two-micron thulium fiber laser
No full textThe short wavelength limit of a thulium fiber laser is investigated. Wavelength tuning from 1720nm to 1660nm was demonstrated and fixed wavelength operation up to 12.6W at 1726nm with slope efficiency of 67% was achieved
Ultra-short wavelength operation of a thulium fibre laser in the 1660-1750nm wavelength band
No full textUltra-short wavelength operation of a thulium fibre laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable fibre laser source operating from 1660nm to 1720nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium fibre lasers in this band, fixed wavelength operation at 1726nm with output power up 12.6W and with slope efficiency >60% is also shown
Metal coated active fibres for high power and lightweight laser designs
No full textWe introduce a novel metal coated active fibre design for use in high power fibre laser systems. Comparisons with polymer coated fibres as well as the prospects of kW level power scaling will be discussed
Thermally-guided fiber-rod laser
No full textFiber and bulk lasers form two distinct classes of solid-state laser, both of which have achieved tremendous success in various arenas, but they are not without their limitations. The long, thin geometry of a fiber allows excellent heat dissipation, which combined with a waveguiding structure provides stronger resilience to thermally-induced mode distortions than in bulk lasers, allowing diffraction-limited single-mode operation at multi-kW power levels in continuous-wave mode. However, the threshold for deleterious non-linear effects and laser-induced damage in fibers is generally much lower than bulk systems, owing to very tight beam confinement over a long interaction length, placing stringent limitations on pulsed performance in fibers
Effect of seed linewidth on few-moded fiber amplifiers
No full textSuppression of detrimental modal interference effects within a cladding-pumped multimode thulium fiber amplifier is achieved using variable bandwidth seed source. The amplifier produced pulse energies of 1.1mJ and peak powers over 20kW at 1956nm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Enhanced pump absorption in double-clad fibres using localised laser-machined mode scramblers
No full textA novel method for improving pump absorption efficiency in circular double-clad fibres by laser machining localised pump scramblers at strategic positions along the fibre is reported. Preliminary results for a thulium-doped double-clad fibre indicate that the pump absorption coefficient attainable via this approach is comparable to an equivalent octagonal fibre
Novel technique for the CO<sub>2</sub> laser fabrication of optical devices with sub-micrometer ablation depth precision
No full textWe present novel techniques for the processing of fibre end face and cladding surfaces using a 9.6 µm CO2 laser. We investigate the effects of pulse duration on process parameters
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