1,721,343 research outputs found
A 11.5 W Yb:YAG planar waveguide fabricated via pulsed laser deposition
No full textDataset for the figures in Grant-Jacob, James A, Beecher, Stephen J, Parsonage, Tina L, Hua, Ping, Mackenzie, Jacob I, Shepherd, David P and Eason, Robert W (2015) An 11.5 W Yb:YAG planar waveguide laser fabricated via pulsed laser deposition. Optical Materials Express
Data collection method: Optical spectrum analyzer (Ando AQ6317).</span
Development of short pulse sources at 1.5µm for non-linear propagation studies in optical fibres
No full textThe development of sources of short mode-locked pulses at 1.5µm is described. Pulses of sufficient power in this spectral region are of great interest for the study of non-linear pulse propagation in optical fibres, where the interplay of negative group velocity dispersion and self-phase modulation can lead to soliton formation and pulse compression. Initial work concentrated on a Nd:YAG pumped methane Raman laser at 1.54µm. The use of a high pressure cell and a capillary waveguide reduces the stimulated Raman scattering threshold to just ~190kW. The use of synchronous pumping is shown to reduce this even further, to ~50kW, which is an order of magnitude less than the peak power available from a typical cw pumped, mode-locked and Q-switched Nd:YAG laser. These threshold values are shown to be in close agreement with theoretical predictions. Peak output powers of nearly 70kW are available in bandwidth-limited, 100ps full width half maximum duration pulses. We then describe a Nd:YAG pumped Yb:Er phosphate glass laser, showing it to be a versatile source in the 1.5µm spectral region. Pulsed, cw, mode-locked and Q-switched operation have been demonstrated in bulk and fibre forms. A simple rate equation model of this sensitised 3-level laser system. is shown to be in rough agreement with experimental results, with absorbed power thresholds as low as ~500mW and ~12mW being found in the bulk and fibre forms respectively. Typical mode-locked pulse durations of ~70ps are found and subsequent pulse compression via high order soliton propagation has given pulses of ~400fs. Finally the Yb:Er laser is assessed as a candidate for enhanced mode-locking via a non-linear external cavity, as in the soliton laser
Data for a fibre-laser-pumped, high-energy, mid-IR, picosecond optical parametric oscillator with a high harmonic cavity
No full textData for figures 2 to 6 of L. Xu, H.-Y. Chan, S.-U. Alam, D. J. Richardson, and D. P. Shepherd, "Fiber-laser-pumped, high-energy, mid-IR, picosecond optical parametric oscillator with a high-harmonic cavity," Opt. Lett. 40, 3288-3291 (2015) </span
Glial dependent survival of neurons in Drosophila
No full textAccording to the classical model of insect neurogenesis, neuron fate and survival is determined largely by cell autonomous mechanisms with no requirement for cell-cell interactions to control the total number of neurons. In a recent paper by Booth et al.,[(1)] however, the central tenet of this model has been called into question. Using a combination of mutations and targeted glial ablation, this paper shows that, contrary to common thinking, neuron survival in the embryonic nervous system of Drosophila is dependent upon normal glial function. This surprising result suggests that insect neurogenesis may have more in common with vertebrate neurogenesis than previously thought
Hormones, neuroblasts and the adult insect
No full textInsect neurogenesis has been subjected to extensive study and as a result is regarded as being well understood. It is, therefore, all the more surprising when a fundamentally novel aspects of the process is uncovered. Until recently it was thought that the production of central neurons ceased before the emergence of the adult. Recently, however, Cayre et al. have shown that neurogenesis also occurs in the adult brain. Their studies also show that the rate at which adult neuroblasts divide is controlled by hormones, suggesting that hormones may play a more important role in regulating neurogenesis than previously suspected
Persistent larval sensory neurones are required for the normal development of the adult sensory afferent projections in Drosophila
No full textWe have tested the hypothesis that larval neurones guide growth of adult sensory axons in Drosophila. We show that ablation of larval sensory neurones causes defects in the central projections of adult sensory neurones. Spiralling axons and ectopic projections indicate failure in axon growth guidance. We show that larval sensory neurones are required for peripheral pathfinding, entry into the CNS and growth guidance within the CNS. Ablation of subsets of neurones shows that larval sensory neurones serve specific guidance roles. Dorsal neurones are required for axon guidance across the midline, whereas lateral neurones are required for posterior growth. We conclude that larval sensory neurones pioneer the assembly of sensory arrays in adults.</p
The Last Days of the German Imperial High Seas Fleet
No full text"The German people did not understand the sea. In the hour of its destiny it did not use its fleet. To-day all that I can do for the fleet is to write its epitaph." | With these words Grand Admiral Alfred von Tirpitz, the creator of the German High Seas Fleet, concluded his memoirs. At the beginning of World War I, Tirpitz expected the German Navy to break the back of British sea power, but this dream ended rudely at Scapa Flow where the mighty German battlefleet was scuttled by its own crews.ProQuest Traditional Publishing Optio
Thermally diffused waveguides in YVO<sub>4</sub>
No full textLasers based on planar optical waveguides have recently generated interest for use as high-average-power sources, due to a combination of attractive features including high optical gain, good thermal-power handling and compatibility with the geometry of high-power diode pump sources [1,2]. However, high-power diode pumping of monolithic plane-plane waveguide cavities generally leads to multi-mode output. One possible route to controlling the spatial output of such devices is through the use of tapered waveguides [3]. For devices of a few centimetres in length, adiabatic expansion can be achieved up to widths of a few hundred microns. This leads to structures compatible with end-pumping by broad-stripe diodes or, for higher power, side-pumping by diode bars. The latter route requires a very strong absorption of the diode emission, as the absorbing length is only a few hundred microns. Thus we have investigated thermal diffusion in YVO4 as a potential waveguide fabrication technique that is compatible with the patterning required for tapered waveguides
- …
