1,720,963 research outputs found
Simple scheme for single-ended operation of a cladding-pumped fiber laser
No full textA novel, all-fiber geometry for achieving predominantly single-ended laser operation without the use of high reflectivity dielectric coatings or in-fiber Bragg gratings is described. Preliminary results for a cladding-pumped Yb-doped fiber laser are reported
Novel approach for single-ended operation of a cladding-pumped fibre laser
No full textA novel, all-fibre geometry for achieving predominantly single-ended laser operation of a fibre laser without the use of high reflectivity dielectric coatings or in-fibre Bragg gratings is described. This approach has been applied to a simple cladding-pumped Yb-doped silica fibre laser pumped by a high-power diode source at ~976 nm. In preliminary experiments the fibre laser yielded 29 W of output at 1080 nm for 48 W of launched pump power. At pump powers over 25 W the slope efficiency with respect to absorbed pump power was 78%. The prospects for further improvement in performance and higher output power are considered
Ultra-low feedback fibre end termination geometry for high power fibre source applications
No full textOptical fibre end termination techniques are very important in the development of fibre-based optical communication systems and high-power fibre sources in laser, amplifier and superfluorescent configurations. There are many situations where unwanted optical feedback from a fibre end-facet can be very detrimental to the performance of the fibre source. For example, in laser configurations in which an external cavity is employed to extend the functionality (e.g. for Q-switching, mode-locking or wavelength tuning), then feedback from the fibre end-facet adjacent to the external cavity will compete with the feedback provided by the external cavity itself and hence may impact adversely on the laser output characteristics
Single mode operation of a large mode area thulium fibre laser using a novel wavelength selective mode filter
No full textImpact of modal interference on the output beam properties of large-core cladding-pumped fiber amplifiers
No full textModal interference in few-moded large-core fiber amplifiers can yield output beams with good beam quality (M ~ 1.2 - 1.4) giving the impression of single-mode operation despite significant higher-order mode content. The implications for high-power devices are discussed
Novel technique for mode selection in a large-mode-area fiber laser
No full textA novel method for selectively exciting a single-spatial-mode (fundamental or higher-order) in a high-power multi-mode fiber laser resonator is presented. Preliminary results for a cladding-pumped Tm-doped silica fiber laser are discussed
Novel technique for mode selection in a multimode fiber laser
No full textA simple technique for transverse mode selection in a large-mode-area (multimode) fiber laser is described. The technique exploits the different spectral responses of feedback elements based on a fiber Bragg grating and a volume Bragg grating to achieve wavelength-dependent mode filtering. This approach has been applied to a cladding-pumped thulium-doped fiber laser with a multimode core to achieve a single-spatial-mode output beam with a beam propagation factor (M2) of 1.05 at 1923 nm. Without mode selection the free-running fiber laser has a multimode output beam with an M2 parameter of 3.3. Selective excitation of higher order modes is also possible via the technique and preliminary results for laser oscillation on the LP11 mode are also discussed along with the prospects for scaling to higher power level
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
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