1,721,046 research outputs found
Direct writing of waveguides is a versatile approach to sensor technology
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Efficient single-axial-mode operation of a Ho:YAG ring laser pumped by a Tm-doped silica fiber laser
No full textEfficient single-frequency operation of a Ho:YAG ring laser at room temperature with a traveling-wave TeO2 acousto-optic modulator to enforce unidirectional operation is reported. By use of a 2-at.% Ho3+-doped 10-mm-long Ho:YAG rod, end pumped by a cladding-pumped tunable Tm-doped silica fiber operating at 1.9 µm, the Ho:YAG ring laser yielded 3.7 W of single-frequency output at 2.1 µm in a diffraction-limited TEM_00 beam with M2 < 1.1 for an incident pump power of 8.8 W. The rf power required for unidirectional operation was 0.3 W and corresponded to an increase in cavity loss for the lasing direction (due to diffraction) of only 0.5%. The prospects for further improvement in efficiency are discussed
Helical-core ytterbium-doped fibre laser
No full textAn Yb-doped fibre laser with a helical core trajectory in the cladding material has been demonstrated for the first time. The laser yields 350mW of linearly-polarised, single-spatial-mode output at 1047nm from a multimode core of diameter 26 micron, and numerical aperture 0.14, when core-pumped by an Yb:YAG laser at 1030nm
Direct UV writing of channel waveguides and Bragg grating structures
No full textDirect UV writing is a dynamic planar lightwave circuit fabrication technique offering great potential as a means of rapid prototyping and small/medium batch fabrication. The technique is based on the refractive index increase of photosensitive glasses through exposure to ultraviolet light. In this case, a beam is tightly focused to create a writing spot in the order of microns and is translated relative to the sample. It is this translation over a 2-d plane that defines the channel waveguide structures; there is no need for a photolithographic mask or subsequent processing. This process has previously been shown to be a versatile system producing good quality, low loss waveguides compatible with existing silica based telecom fibres
Single step writing of equalised bandwidth Bragg gratings within planar light-wave circuits
No full textWe demonstrate single-step writing of waveguide circuits with Bragg gratings between 1227nm and 1687nm and for the first time show that the grating bandwidth can be normalised over this large wavelength range
Efficient Tm:silica fiber laser pumped Ho:YAG lasers
No full textHo:YAG lasers employing standing-wave and ring cavity configurations have yielded 6.4W of multi-axial-mode output and 3.7W of single-axial-mode output at 2.1 µm respectively for <9.6W of incident pump power at ~1.9 µm from a cladding-pumped Tm:silica fiber laser
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
3.7-Watt single-frequency cw Ho:YAG ring laser end-pumped by cladding-pumped Tm-doped silica fibre laser
No full textAcousto-optically induced unidirectional operation of a Ho:YAG ring laser pumped by a Tm-doped silica fibre laser has been demonstrated. 3.7W of single-frequency output at 2114nm for 8.8W of incident pump power at 1905nm was obtained
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