1,721,019 research outputs found
Dataset for Amplification of a radially polarised beam in an Yb:YAG thin-slab
No full textRaw Data
Funded by Fianium and the Engineering Physical Sciences Research Council (EPSRC) for an Industrial CASE studentship.</span
Power Scaling Architectures for Solid-State and Fiber Lasers
No full textThis thesis focuses on developing power scaling architectures for solid-state and fiber lasers. The thermally-guided fiber-rod (TGFR) laser is suggested as a novel power scalable concept. This device lies in a domain between bulk rod lasers and traditional fiber lasers. The motivation is to benefit from the excellent thermal management properties of fibers, whilst negating deleterious nonlinear effects owing to the tight beam confinement and long interaction lengths that plague high power fiber lasers. An elegant thermal guiding technique is proposed to provide mode control with the TGFR. We derive the refractive index profile that ensues as a result of end-pumping the TGFR with a fiber-coupled diode laser. Furthermore, we construct a model that predicts the resulting impact on Gaussian beam propagation through the TGFR for various pump configurations. A model describing the gain within the device is derived from the laser rate equations. These two models allow us to predict amplifier and laser performance of the TGFR device.We initially suggest soft glass as a host material for the TGFR, owing to the ability to dope this material with rare-earth ions in significantly higher concentrations than silica which is the traditional material of choice for fiber lasers, thus allowing the realisation of shorter devices. The requirements of a soft glass host are discussed in terms of both device fabrication and laser operation. Three potential sources are identified, including an in-house manufactured neodymium-doped and undoped phosphate glass, a commercial neodymium-doped and undoped silicate glass, and a neodymium-doped and undoped phosphate glass obtained through collaboration. The fabrication of potential TGFR devices with these three sources is described. This is followed by a laser investigation of these devices, where the issues of glass homogeneity and transmission loss become apparent, which are largely attributed to poor glass quality and unsuitable compatibility between the doped and undoped glasses. The neodymium-doped phosphate obtained through collaboration performed best, with a maximum output power around 1054nm of 2.5W, with a slope efficiency with respect to launched pump power of 28.5%. However, the poor glass quality prevented the thermal guiding investigation, and thus the beam quality was dictated by the highly multimode guide, resulting in a beam propagation factor of M2 = 60. Additionally, although this device had the lowest loss of the three sources, a significant loss of 5.7dB/m was measured using the Findlay-Clay analysis.In light of these glass quality issues, the TGFR concept was fully tested using an extra-large mode area silica fiber. A mode guiding investigation revealed that an in-built non-uniform refractive index profile was responsible for providing a degree of guiding, even in the absence of pumping. This guiding was well predicted by assuming a parabolic refractive index profile and utilising the mode guiding model. Furthermore, the thermal guiding model gave excellent agreement with measured data across a range of launched pump powers up to 30W. The device was operated as an amplifier for seed beams at 976nm and 1030nm, and good agreement with the gain model was observed. At 976nm a maximum gain of 4.1dB was achieved for a 60mW seed resulting in an output power of 155mW, and 2.2dB for a 450mW seed resulting in an output power of 750mW. For 1030nm a maximum gain of 5.0dB was achieved for a 50mW seed resulting in an output power of 160mW, and 3.9dB for a 1.1W seed resulting in an output power of 2.7W. Excellent beam quality was maintained throughout amplification with M2 < 1.1 at the maximum gain levels for both 976nm and 1030nm. The concept was extended to a laser configuration at for both the 975nm and 1030nm transition. A device operating at 1032.5nm achieving a maximum output power of 13.1W with a slope efficiency of 44% with respect to launched power and 53% with respect to absorbed power. Excellent beam quality was achieved at maximum output power with M2 < 1.1. Additionally, a device operating at 978.5nm achieved a maximum output power of 1W with a slope efficiency of 8% with respect to launched power. Again, excellent beam quality was achieved at maximum output power with M2 < 1.1. The slope efficiencies of both of these devices, particularly the latter, are expected to increase with higher pump powers.An Yb:YAG thin-slab architecture is suggested as a power scalable architecture for cylindrical vector (CV) beams, which have promising applications within materials processing. A seed source is constructed for operation at 1030nm, which exploits thermally-induced bi-focusing to produce a radially polarised output beam with a maximum output power of 6.9W, with a conversion efficiency of 41% with respect to absorbed pump power. The beam quality was measured as M2 = 2.3, whilst the radial polarisation extinction ratio (RPER) was > 15dB. It was demonstrated that the seed source could be amplified in a highly asymmetric thin-slab gain medium whilst maintaining radial polarisation purity. The implications of the Gouy phase shift owing to astigmatic focusing within the slab are discussed. Amplifier experiments yielded a gain of 7.5dB for a 25mW seed input power, and 4.4dB for a 1.45W seed input power, resulting in a maximum output power of 4W.The beam propagation factor at the maximum gain level was maintained at the lowest seed input power at M2 = 2.3, and was only slightly degraded to M2 = 2.4 at the highest seed input powers. Crucially, the RPER was maintained at >15dB for both cases
Dataset for Method for generating high purity Laguerre-Gaussian vortex modes paper
No full textDataset for:
Clarkson, W. et al (2019). Method for Generating High Purity Laguerre-Gaussian Modes. IEEE Journal of Quantum Electronics 55(5).</span
Amplification of a radially-polarised beam in an Yb:YAG thin slab
No full textAmplification of an axially-symmetric, doughnut-shaped radially-polarised beam at 1030nm in a diode-bar-pumped double-pass thin Yb:YAG slab amplifier architecture without degradation in polarisation purity is demonstrated. Preliminary experiments yielded a small-signal gain of 9dB for 50W of incident pump power while maintaining the polarisation purity of the seed beam
Data set for Thermally-guided Yb-doped fiber-rod amplifier and laser
No full textData set for the paper Smith, C. R., Simakov, N., Hemming, A., & Clarkson, W. A. (2019). Thermally-guided Yb-doped fiber-rod amplifier and laser. Applied Physics B: Lasers and Optics, 125(32), 1-10. DOI: 10.1007/s00340-018-7126-3</span
Method for generating high purity Laguerre-Gaussian modes
No full textGeneration of a donut-shaped first-order Laguerre-Gaussian (LG01) vortex mode via a method designed to yield high mode purity is reported. Our approach utilises a novel twin-spot end-pumping scheme to directly excite the first order Hermite-Gaussian (HG01) mode in a solid-state laser, followed by a novel astigmatic mode converter based on spherical (concave) mirrors aligned at oblique incidence. A simple theoretical model for the mode converter is derived and from this the design approach is explained along with the potential benefits compared to conventional schemes based cylindrical-lens astigmatic mode converters, particularly for power scaling. As a proof-of-principle and to confirm the benefits of this scheme in terms of high mode purity we have applied it to an end-pumped Nd:YVO4 laser to generate a (LG01) beam with a controllable sense of azimuthal phase and hence orbital angular momentum. A method for characterising the resulting beam based on analysis of the spiral interference pattern derived with the aid of a Mach-Zehnder interferometer is described and yields a value for the LG01 mode purity of 94%. Common sources of mode impurity are identified and the prospects for scaling to higher power whilst maintaining high mode purity are considered
Thermally-guided Yb-doped fiber-rod amplifier and laser
No full textIn this paper we describe a thermally-guided fiber-rod amplifier and laser oscillator, which exploit thermal guiding to achieve mode control. This power scalable approach operates with mode sizes that are typically an order of magnitude larger than traditional single-mode fibers. Operating as an amplifier we achieve a small-signal gain of 5dB at 1030nm, whilst maintaining excellent beam quality (M2 < 1.1). In a laser configuration we obtained 13.1W of diffraction-limited (M2 < 1.1) output power at 1032.5nm, with a slope efficiency 53% with respect to absorbed power. A model predicting beam evolution through the thermally-guided fiber-rod gain medium is presented and validated
Dataset to support the paper '33 W radially polarized emission from a double-pass Ho:YAG thin-slab amplifier'
No full textDataset for '33 W radially polarized emission from a double-pass Ho:YAG thin-slab amplifier' in Journal of the Optical Society of America B.
This dataset contains the data used in the generation of Figures 2 and 4 in the manuscript.
The figures are as follows:
Fig. 2. Output power curve for the radially polarized Ho:YAG seed laser. Inset, top-left: emission spectrum at 13.2 W. Inset, bottom-right: near-field ring-shaped pump beam profile.
Fig. 4. Output power curve for the Ho:YAG thin-slab amplifier with a 13.2 W seed input. Inset, top-left: simulated variation in pump and seed beam areas along the length of the crystal. Inset, bottom-right: amplifier gain versus absorbed pump.</span
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
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