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Laser Interactions for the Synthesis and In Situ Diagnostics of Nanomaterials

Description: Laser interactions have traditionall been at thec center of nanomaterials science, providing highly nonequilibrium growth conditions to enable the syn- thesis of novel new nanoparticles, nanotubes, and nanowires with metastable phases. Simultaneously, lasers provide unique opportunities for the remote char- acterization of nanomaterial size, structure, and composition through tunable laser spectroscopy, scattering, and imaging. Pulsed lasers offer the opportunity, there- fore, to supply the required energy and excitation to both control and understand the growth processes of nanomaterials, providing valuable views of the typically nonequilibrium growth kinetics and intermediates involved. Here we illustrate the key challenges and progress in laser interactions for the synthesis and in situ diagnostics of nanomaterials through recent examples involving primarily carbon nanomaterials, including the pulsed growth of carbon nanotubes and graphene.
Date: January 1, 2014
Creator: Geohegan, David B.; Puretzky, Alexander A.; Yoon, Mina; Eres, Gyula; Rouleau, Christopher; Xiao, Kai et al.
Partner: UNT Libraries Government Documents Department

Field Evaluation of the U.S. Army Engineer Topographic Laboratories' Laser Dam Alignment Instrument

Description: Summary: Several series of laser instrument alignment surveys were made at the exterior roadway deck level and within the interior inspection gallery of Keystone Dam, Oklahoma, and compared with theodolite surveys over the same lines and under similar conditions.
Date: April 1973
Creator: Davis, Carl D.
Partner: UNT Libraries Government Documents Department

Free-Electron Lasers: Present Status and Future Prospects

Description: Free-electron lasers as scientific instruments are reviewed. The present status and future prospects are delineated with attention drawn to the size, complexity, availability, and performance capability of this new tool. The Free-Electron Laser (FEL) was proposed by John Madey in 1970 (1), although earlier work, relevant to the concept, had been performed by Motz (2) and by Phillips (3). Experimental demonstration was achieved by Madey, et. al. in 1975 and 1976 (4). Since that time, FELs of diverse configurations have been operated at several laboratories around the world. At present, FEL development is focused in two directions: in constructing reliable FELs for scientific research and in extending FEL capability to vacuum ultra-violet (VUV) and even shorter wavelengths. In this article we shall only very briefly review the principles of an FEL, putting emphasis on those aspects that limit performance, after which we shall discuss the applications, present status and future prospects of FELs. Much material that we wish to present is in the form of Tables, and they are an essential part of this article.
Date: May 1, 1990
Creator: Kim, K.-J. & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department


Description: Two independently-driven laser accelerators were operated together in series for the first time in a proof-of-principle experiment to demonstrate staging. The ability to stage together these devices is important for eventually building practical laser-driven accelerators. The laser accelerators consisted of two identical inverse free electron lasers (IFEL), where the first IFEL served as a prebuncher, which created {approx}3-fs long microbunches that were accelerated by the second IFEL. Precise and stable control of the phasing between the microbunches and laser wave inside the second IFEL was demonstrated. The effects of over-modulation of the prebuncher were also investigated. In all cases there was good agreement with the model. Additional details of the microbunch characteristics could be inferred by using the model. Plans for demonstrating monoenergetic laser acceleration are also presented.
Date: June 18, 2001
Creator: Kimura, W. D.; Campbell, L. P.; DILLEY,C.E.; Gottschalk, S. C.; Quimby, D. C.; BABZIEN,M. BEN-ZVI,I. et al.
Partner: UNT Libraries Government Documents Department

Limits to Electron Beam Emittance from Stochastic Coulomb Interactions

Description: Dense electron beams can now be generated on an ultrafast timescale using laser driven photo-cathodes and these are used for a range of applications from ultrafast electron defraction to free electron lasers. Here we determine a lower bound to the emittance of an electron beam limited by fundamental stochastic Coulomb interactions.
Date: August 22, 2008
Creator: Coleman-Smith, Christopher; Padmore, Howard A. & Wan, Weishi
Partner: UNT Libraries Government Documents Department

Time Resolved Shadowgraph Images of Silicon during Laser Ablation:Shockwaves and Particle Generation

Description: Time resolved shadowgraph images were recorded of shockwaves and particle ejection from silicon during laser ablation. Particle ejection and expansion were correlated to an internal shockwave resonating between the shockwave front and the target surface. The number of particles ablated increased with laser energy and was related to the crater volume.
Date: May 6, 2006
Creator: Liu, C.Y.; Mao, X.L.; Greif, R. & Russo, R.E.
Partner: UNT Libraries Government Documents Department

Short-pulse Laser Capability on the Mercury Laser System

Description: Applications using high energy ''petawatt-class'' laser drivers operating at repetition rates beyond 0.01 Hz are only now being envisioned. The Mercury laser system is designed to operate at 100 J/pulse at 10 Hz. We investigate the potential of configuring the Mercury laser to produce a rep-rated, ''petawatt-class'' source. The Mercury laser is a prototype of a high energy, high repetition rate source (100 J, 10 Hz). The design of the Mercury laser is based on the ability to scale in energy through scaling in aperture. Mercury is one of several 100 J, high repetition rate (10 Hz) lasers sources currently under development (HALNA, LUCIA, POLARIS). We examine the possibility of using Mercury as a pump source for a high irradiance ''petawatt-class'' source: either as a pump laser for an average power Ti:Sapphire laser, or as a pump laser for OPCPA based on YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), ideally producing a source approaching 30 J /30 fs /10 Hz--a high repetition rate petawatt. A comparison of the two systems with nominal configurations and efficiencies is shown in Table 1.
Date: June 22, 2006
Creator: Ebbers, C; Armstrong, P; Bayramian, A; Barty, C J; Bibeau, C; Britten, J et al.
Partner: UNT Libraries Government Documents Department

The effect of temporal pulse shape on optical damage

Description: The conditions under which optical materials are susceptible to laser-induced damage is a topic which has been the subject of considerable study. Laser parameters such as wavelength and temporal pulse duration have been studied extensively. Until this work the effect of temporal pulse shape has not been considered. We present here data from a simple single-parameter model and a supporting experiment which predicts that a Flat-In-Time-pulse will produce damage at approximately 80% of the fluence of a Gaussian pulse of the same FWHM duration.
Date: August 15, 2006
Creator: Carr, C W; Trenholme, J B & Spaeth, M L
Partner: UNT Libraries Government Documents Department

Multimode-diode-pumped gas (alkali-vapor) laser

Description: We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of {approx}1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.
Date: August 22, 2005
Creator: Page, R H; Beach, R J & Kanz, V K
Partner: UNT Libraries Government Documents Department

The effect of multiple wavelengths on Laser-induced damage in DKDP crystals

Description: Laser-induced damage is a key factor that constrains how optical materials are used in high-power laser systems. In this work the size and density of bulk laser-induced damage sites formed during frequency tripling in a DKDP crystal are studied. The characteristics of the damage sites formed during tripling, where 1053-nm, 526-nm, and 351-nm light is simultaneously present, are compared to damage sites formed by 351-nm light alone. The fluence of each wavelength is calculated as a function of depth with a full 4D(x,y,z,t) frequency conversion code and compared to measured damage density and size distributions. The density of damage is found be predominantly governed by 351-nm light with some lesser, though non-negligible contribution from 526-nm light. The morphology of the damage sites, however, is seen to be relatively insensitive to wavelength and depend only on total fluence of all wavelengths present.
Date: July 11, 2005
Creator: Carr, C W & Auerbach, J M
Partner: UNT Libraries Government Documents Department

Survey of Laser Markets Relevant to Inertial Fusion Energy Drivers, information for National Research Council

Description: Development of a new technology for commercial application can be significantly accelerated by leveraging related technologies used in other markets. Synergies across multiple application domains attract research and development (R and D) talent - widening the innovation pipeline - and increases the market demand in common components and subsystems to provide performance improvements and cost reductions. For these reasons, driver development plans for inertial fusion energy (IFE) should consider the non-fusion technology base that can be lveraged for application to IFE. At this time, two laser driver technologies are being proposed for IFE: solid-state lasers (SSLs) and KrF gas (excimer) lasers. This document provides a brief survey of organizations actively engaged in these technologies. This is intended to facilitate comparison of the opportunities for leveraging the larger technical community for IFE laser driver development. They have included tables that summarize the commercial organizations selling solid-state and KrF lasers, and a brief summary of organizations actively engaged in R and D on these technologies.
Date: February 24, 2011
Creator: Bayramian, A. J.; Deri, R. J. & Erlandson, A. C.
Partner: UNT Libraries Government Documents Department

Feasibility and advantages of off-resonance lasers in chemically reacting systems

Description: The problem of understanding the semiclassical description of the time evolution of an ensemble of two state systems under the influence of a coherent radiation field is of considerable importance. Previous attempts to deal with these problems have dealt with either broad pulses or ultrashort pulses which allow the use of the rate equations or finite phase memory to be incorporated into the description. In neither case, however, has the effect of incoherent feeding and off-resonance effects in a coherently driven two-level system been analyzed. A closed form solution that includes the effects of relaxation and spontaneous emission between the two levels has been obtained for the general case when the ensemble is being incoherently fed from a population reservoir, as would be the case, for example, in a chemical laser. In addition to providing a basis for understanding the modifications which occur for such a system, the mathematical formulation predicts that an important effect may be observed. This effect, which is termed ''kinetic coherence,'' is the production of a long-term coherent component that results directly from the kinetic feeding. The magnitude of the component is related to the rate of creating excited states, relaxation pathways and the off-resonance frequency. It is shown how, in principle, it is possible to utilize these off-resonance effects in any inhomogeneously broadened system to significantly overcome the losses from T$sub 2$ relaxation processes and to provide an experimental system capable of controlling the relative ratio of spontaneous and stimulated emission. Finally, the relationships between chemical kinetics, the off-resonance feature and sustained self-regulation in a system exhibiting gain are discussed. (auth)
Date: June 1, 1975
Creator: Harris, C.B.
Partner: UNT Libraries Government Documents Department

Techniques for synchronization of X-Ray pulses to the pump laser in an ultrafast X-Ray facility

Description: Accurate timing of ultrafast x-ray probe pulses emitted from a synchrotron radiation source with respect to the signal initiating a process in the sample under study is critical for the investigation of structural dynamics in the femtosecond regime. We describe schemes for achieving accurate timing of femtosecond x-ray synchrotron radiation pulses relative to a pump laser, where x-rays pulses of <100 fs duration are generated from the proposed LUX source based on a recirculating superconducting linac. We present a description of the timing signal generation and distribution systems to minimize timing jitter of the x-rays relative to the experimental lasers.
Date: May 6, 2003
Creator: Corlett, J.N.; Doolittle, L.; Schoenlein, R.; Staples, J.; Wilcox, R. & Zholents, A.
Partner: UNT Libraries Government Documents Department