1,721,094 research outputs found
Reducing loss in practical single ring antiresonant hollow core fibres
No full textFibres that guide light in a large hollow core and in a single spatial mode are becoming increasingly important in the delivery of multi-MW peak power beams and to exploit nonlinear dynamics in gases. For high peak power beam delivery a large air core can prevent fibre damage and catastrophic self-focusing effects. Current hollow core fibre (HCF) types include photonic band gap (PBG) and Kagome fibres which rely on a periodically structured and therefore complex and extended cladding [1,2]. A simplified HCF fibre with a single antiresonant glass ring around the core and low loss at yellow wavelengths was recently reported [3]. Here we present an improved fibre design with a lower minimum loss (below 1dB/m) in the near infrared. Stable drawing conditions allow the repeatable fabrication of long lengths of fibre
Low loss antiresonant hollow core fibres
No full textWe study the loss mechanisms in novel antiresonant hollow-core fibres and demonstrate the importance of optimising the air-cladding thickness and reducing the node size. Based on these rules we fabricate fibres with wide-bandwidth and low-loss
High-power Er:YAG laser with quasi-top-hat output beam
No full textA simple method for simultaneously exciting the fundamental (TEM00) transverse mode and first order Laguerre-Gaussian (LG01) donut mode in an end-pumped solid-state laser to yield a quasi-top-hat output beam is reported. This approach has been applied to an Er:YAG laser, in-band pumped by an Er,Yb fiber laser, yielding 9.6 W of continuous-wave output at 1645 nm in a top-hat-like beam with beam propagation factor (M2) < 2.1 for 24 W of incident pump power at 1532 nm. The corresponding slope efficiency with respect to incident pump power was 49%. The prospects of further scaling of output power and improved overall efficiency are considered
Microstructured cladding elements to enhance performance and flexibility of large mode area leakage channel fibers
No full textLarge mode area fibers are imperative for scaling up the average power of fiber lasers. Single-mode behavior and low FM loss are the crucial functionalities for these fibers. However, for key applications such as picosecond pulsed lasers, the device length needs to at least a few meters. This makes a certain degree of bend tolerance a prerequisite in the fiber design. While rod-type PCFs have been very successful in offering large mode areas, their rigid configuration limits their application domain. Alternatively, leakage channel fibers (LCFs) have shown a great potential for offering substantial bend tolerance along with large mode areas. However, the proposed use of Fluorine-doped rods in the all-solid version limits their practical design space. Here, we propose a novel design concept to attain single-material, large mode area fibers (mode area >~ 1000µm2) with effectively single mode operation coupled with bending characteristics comparable to all-solid LCFs and greater design flexibility and easier splicing that is comparable to rod-type PCFs
Optimising the performances of hollow antiresonant fibres
Full text linkWe study the loss of novel antiresonant hollow-core fibres, demonstrate the existence of a wavelength independent optimum distance between core-surround and solid outer cladding, and provide useful guidelines for the fabrication of practical low-loss fibres
High-energy Q-switched Er:YAG laser with Laguerre-Gaussian (LG01) mode output
No full textA simple method to allow direct excitation of the first-order Laguerre-Gaussian mode has been applied to a fibre-laser-pumped Q-switched Er:YAG laser yielding a maximum pulse energy of 18mJ in a 40ns duration pulse at 1617nm
High-power fibre-laser-pumped Er:YAG laser with top-hat output beam
No full textA simple method to generate the first-order Laguerre-Gaussian mode or a top-hat beam from an Er:YAG laser is reported. The efficient laser produced 13.1W in a LG01 mode and 9.6W with a top-hat beam
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
Emerging optical fibre technologies with potential defence applications
No full textRecent years have seen the development of a range of promising optical fibre technologies emerge, enabled by advances in materials and fabrication techniques. We describe 3 emerging areas in optical fibre developments: nanomechanical optical fibres, microstructured hollow core silica fibres for high peak optical power and/or extended infrared transmission, and chalcogenide glasses and fibres for mid-IR applications
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