6,441 research outputs found
Pulse-pumping of cascaded Raman fibre amplifiers
No full textIn this thesis, I investigate cascaded Raman fibre amplifiers (RFAs) pumped with shaped optical pulses delivered from a Yb doped fibre MOPA source. RFAs offer the potential to generate gain at any arbitrary wavelength with an appropriate pump source, limited only by the fibre’s transparency range. The use of a counter-propagating signal and pump creates a continuous gain, despite the instantaneous nature of stimulated Raman scattering (SRS). A high power Yb doped fibre source emitting around the 1050 to 1100 nm region offers a flexible pump source that can in principle be used to generate gain for any signal from ~1100 to 2000 nm in a silica-based fibre via cascaded SRS. This opens up opportunities for an ultrabroadband amplifier with unmatched spectral width. Furthermore, by using a pump source that is in a MOPA configuration there is a high degree of control over the output characteristics which offers the potential of near-instantaneous electronic control of ultra-broadband Raman gain spectra. In the simplest configuration, cascaded Raman wavelength shifting across a wide range of wavelengths using single-level pump pulses (i.e., approximate super-Gaussian pulses) is investigated. Using a silica-based highly nonlinear fibre (HNLF), cascaded Raman wavelength shifting up to seven Stokes orders is demonstrated and counter-propagating gain measurements are made across all seven Stokes orders. From a pump wavelength of 1064 nm, the peak gain of the 7th Stokes order was ~1575 nm which demonstrated the potential for gain covering more than 500 nm. I believe this is the first time such a measurement has been undertaken. Other fibre types were also studied for comparison. Furthermore, the noise performance and gain saturation properties of cascaded RFAs were investigated, as well. In a more advanced configuration, the Raman gain spectra produced from pumping the HNLF with step-shaped pump pulses are investigated. Such pulses consist of multiple levels with different, controllable, instantaneous powers. By adjusting the power of each step appropriately I show that different parts of the pulse transfer their energy to different Stokes orders, leading to a controllable gain spectrum covering multiple Stokes orders at the same time. I further study how the gain spectrum can be controlled by manipulating the individual duty cycle of each section of the step-shaped pump pulses as well as using multiple pump wavelengths in a time-division multiplexed pumping scheme. Single and dual wavelength pumping of various fibres with step-shaped pulses was experimentally demonstrated. Raman gain spectra spanning two and three Stokes orders and covering over 100 nm were realised. Computer simulations are also carried out for pumping with more than two pump wavelengths and for gain spectra targeting gain simultaneously up to seven Stokes orders and covering up to ~500 nm. This shows that the use of step-shaped pulses and multiple pump wavelengths allow for further increase and control of the useable bandwidth
William Farrell photograph
No full textThis photograph of William Farrell is from the Northwest Territory Celebration trek and shows him standing on the bank of a river.
The 1937-1938 Northwest Territory Sesquicentennial Celebration was a federally funded yearlong celebration which commemorated the journey of the Ohio Company of Associates of 48 men who traveled westward from Ipswich, Massachusetts to Marietta, Ohio in 1787. A main feature of the celebration was to recruit a caravan of 38 men to re-create the journey. At each stop along the 52 day trek, the pioneers presented a pageant called “Freedom on the March.” In West Newton, Pennsylvania, the participants were given tools of the 1700s to build a flat boat and canoes to travel to Marietta, Ohio. The men stayed in touch with reunions over the years, and Carl Givler and four other men had a final reunion reenactment of the 1937 trek in 1987
Upward Pricing Pressure and Critical Loss Analysis: Response
No full textWe propose that this measure ("UPP") be used as an indicator of the merger’s likely unilateral effects. Joseph Farrell (FTC) & Carl Shapiro (DOJ).
Legislate or Delegate? Bargaining over Implementation and Legislative Authority in the European Union
No full textIn this article we explain how actors' ability to bargain successfully in order to advance their institutional preferences has changed over time as a function of the particular institutional context. We show how actors use their bargaining power under given institutional rules in order to shift the existing balance between legislation and delegation, and shift the rules governing delegation in their favor, between formal treaty changes. We argue that a collective actor's preferences over delegation is a function of whether the actor has more ability to influence policy through delegation or through legislation. We go on to argue that the degree to which a specific actor's preferences can prevail (in a setting in which different actors have different preferences) will depend upon its bargaining power under existing institutional rules, i.e. its ability to impede or veto policy in order to change the division between legislation and delegation and the rules of delegation. Our primary focus in this article is on choice over procedure; i.e. the battles over whether or not delegation or legislation should be employed. We maintain a secondary focus on change in procedure, examining how different procedures of comitology have come into being and been removed from the table. We examine the evolution of the debate over comitology and implementation, over five key periods. We scrutinize how actors within these periods seek to shift the balance of legislation and delegation and the rules of delegation according to their preferences. Our conclusions assess our empirical findings on the basis of our model.accountability; European Commission; Council of Ministers; European Parliament; European Parliament
Genesis Breyer P-Orridge : Sacred Intent : Conversations with Carl Abrahamsson 1986–2019
No full text"Three decades of conversations with Genesis Breyer P-Orridge, provocateur, artist, gender revolutionary and leader of the bands Throbbing Gristle, Psychic TV and more
Published for legendary artist and musician Genesis Breyer P-Orridge’s 70th birthday in 2020, Sacred Intent gathers conversations between Breyer P-Orridge and his friend and collaborator, the Swedish author Carl Abrahamsson. From the first 1986 fanzine-based interview about current projects, philosophical insights, magical workings, international travels, art theory and gender revolutions, to 2019’s thoughts on life and death in the the shadow of battling leukaemia, Sacred Intent is a unique journey in which the art of conversation blooms to the highest degree." -- Distributor's website
Spectral gain control using shaped pump pulses in a counter-pumped cascaded fiber Raman amplifier
No full textWe investigate the Raman gain spectra produced from pulse-pumping a highly nonlinear fiber with shaped optical pulses delivered from a Yb-doped fiber MOPA pump source. Cascaded Raman wavelength shifting up to seven Stokes orders is demonstrated and the counter-propagating gain is measured across all seven Stokes orders. Step-shaped optical pulses with varying instantaneous powers are then used to pump the highly nonlinear fiber, generating a controllable gain spectrum across multiple Stokes orders. Furthermore, we extend this work by using multiple pump wavelengths along with step-shaped pulses to increase the bandwidth of the Raman gain spectrum
Letter from Herbert Babbitt to Carl Hayden
No full textLetter from Herbert Babbitt to Carl T. Hayden about grazing cattle in the park boundaries
Letter from Bernie Zachau to Carl Hayden
No full textLetter from Bernie Zachau to Carl Hayden regarding water power in the Grand Canyon
Letter from Carl Hayden to Harold Greene
No full textLetter from Carl Hayden to Harold Greene regarding the progress of the national park bill
Scholarly Communication: Solving a Global Crisis - Farrell
No full textThis is part of a presentation from the 2008 12th Biennial CARL Conference. It offers an overview of the history of Scholarly Communication and the Open Access movement, with examples from around the world. Other presentations from this CARL panel are available at: http://carl-acrl.org/Archives/ConferencesArchive/Conference08/during/breakout.htm
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