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Intracavity Frequency Doubling of a Diode-Pumped, External Cavity, Surface Emitting Semiconductor Laser

Description: The authors present a compact, robust, solid-state blue light (490 nm) source capable of greater than 5 mW of output in a TEM{sub 00} mode. This device is an optically pumped, vertical external-cavity surface-emitting laser (VECSEL) with an intracavity frequency doubling crystal.
Date: April 22, 1999
Creator: Alford, W.J.; Allerman, A.A.; Crawford, M.H. & Raymond, T.D.
Partner: UNT Libraries Government Documents Department

Rapport Juin-Juillet 1999

Description: This report describes the optical system which allows the delivery, in an efficient and homogeneous way, of the pump light from the diode arrays of the Mercury laser system described in the two previous reports. I will, first, describe the present pumping line ; the description of the Advanced Pumping Design (APD) being given in the second part of this report.
Date: August 18, 1999
Creator: Bibeau, C & Chanteloupe, J C
Partner: UNT Libraries Government Documents Department

A reliable low-maintenance flashlamp-pumped Ti:sapphire laser operating at 120 PPS

Description: Flashlamp-pumped Ti:sapphire lasers have been reported to produce high-energy pulses with broad tunability. However, with the flashlamps operated close to their explosion energy, and thermal loading effects in the laser rod, these lasers were restricted to low repetition rates (typically around 10 PPS). Higher repetition rates at constant laser pulse energy reduce the flashlamp lifetime drastically. The author reports on a reliable flashlamp-pumped Ti:sapphire laser that has been operating at 120 PPS for over 10{sup 9} shots with the only cavity or pump chamber maintenance being flashlamp changes less than every 2{times}10{sup 8} pulses -- the lowest maintenance reported. A specular dual-lamp pump chamber was used to pump a 4 mm {times} 6 inches, 0.1% doped Ti:sapphire rod. This resulted in a very low lasing threshold, which ensured a stable output at low pump levels. The criterion for pump power was to obtain a highly stable output at the edge of the selected tuning range, from 790 to 860 nm. The combination of flashlamp walls, flashlamp flow tubes, and rod solarization.
Date: March 1, 1994
Creator: Witte, K. H.
Partner: UNT Libraries Government Documents Department


Description: >The optical radiation that occurs in a dynamic plasma pinch experiment depends in part on the amount and type of impurity atoms present in the system. By proper choice of these impurities, it should be possible to tailor the optical radiation from the pinch in intensity, spectrum, and duration such that the kinetic energy of motion (1OO to 1OOO joules) appears as radiation enengy in less than 10/sup -6/ sec. This should provide a good method of optical pumping for pulse optical maser operation. The optical radiation from the dynamic pinch is discussed and an experiment that is being set up to use this radiation as the pump source for an optical maser is described. (auth)
Date: March 31, 1961
Creator: Colgate, S. A. & Trivelpiece, A. W.
Partner: UNT Libraries Government Documents Department

Proceedings of the Workshop on Polarized Targets in Storage Rings. May 17-18, 1984 at Argonne National Laboratory

Description: Proceedings of a workshop of a unique group of physicists in the fields of high-energy, nuclear and atomic physics. The meeting was organized in a manner that stimulated discussion among the 58 participants and focused on developments in polarized target technology and the underlying atomic physics. An impressive array of future possibilities for polarized targets as well as current developments in polarized target technology were discussed at the workshop.
Date: August 1984
Creator: Holt, R. J.
Partner: UNT Libraries Government Documents Department

Vertical Cavity Surface Emitting Lasers

Description: The goal of this project was to increase the power of vertical cavity surface emitting lasers and to convert their wavelength into the blue/ultraviolet and the infrared for sensing applications. We have increased the power to the multi-watt level and have generated several milliwatts of blue light using optical pumping. Electrical pump has been less successful, but we have identified the problems and begun work to overcome them using a bottom emitting design.
Date: November 1, 2002
Partner: UNT Libraries Government Documents Department

Laser-induced reactions in a deep UV resist system: Studied with picosecond infrared spectroscopy

Description: One of the most technologically important uses of organic photochemistry is in the imaging industry where radiation-sensitive organic monomers and polymers are used in photoresists. A widely-used class of compounds for imaging applications are diazoketones; these compounds undergo a photoinduced Wolff rearrangement to form a ketene intermediate which subsequently hydrolyses to a base-soluble, carboxylic acid. Another use of organic molecules in polymer matrices is for dopant induced ablation of polymers. As part of a program to develop diagnostics for laser driven reactions in polymer matrices, we have investigated the photoinduced decomposition of 5-diazo-2,2-dimethyl-1,3-dioxane-4,6-dione (5-diazo Meldrum`s acid, DM) in a PMMA matrix using picosecond infrared spectroscopy. In particular, irradiation of DM with a 60 ps 266 nm laser pulse results in immediate bleaching of the diazo infrared band ({nu} = 2172 cm{sup -1}). Similarly, a new band appears within our instrument response at 2161 cm{sup -1} (FWHM = 29 cm{sup -1}) and is stable to greater than 6 ns.; we assign this band to the ketene photoproduct of the Wolff rearrangement. Using deconvolution techniques we estimate a limit for its rate of formation of {tau} < 20 ps. The linear dependence of the absorbance change with the pump power (266 nm) even above the threshold of ablation suggest that material ejection take place after 6ns.
Date: December 31, 1995
Creator: Lippert, T.; Koskelo, A. & Stoutland, P.O.
Partner: UNT Libraries Government Documents Department

Prospects for fluorescence based imaging/visualization of hydrodynamic systems on the National Ignition Facility

Description: The next generation of large, high power lasers, such as the National Ignition Facility (NIF) [1] in the United States, Laser Mega Joule [2] in France or Helen Successor [3] in the United Kingdom offer the prospect of x-ray fluorescence based diagnosis of hydrodynamic experiments The x-ray fluorescence could be pumped by at least two techniques One technique is to use a sizable fraction of these facilities` high power to efficiently make multi-kilovolt x-rays which, in turn, causes dopants placed in experimental packages to fluoresce We call this ``externally pumped x-ray fluorescence`` The second technique is to use the sizable multi-kilovolt photon background that we expect to be present in many hohlraum based experiments, while the driving laser is on, to pump x-ray fluorescence The fluorescing medium could be a dopant in an experimental package or, possibly, a relatively thick slab of material in the hohlraum wall which could serve as a backlighter We call this ``hohlraum hot-corona pumped fluorescence``.
Date: June 4, 1998
Creator: Suter, L. J., LLNL
Partner: UNT Libraries Government Documents Department

Traveling wave pumping of ultra-short pulse x-ray lasers

Description: Pumping of proposed inner-shell photo-ionized (ISPI) x-ray lasers places stringent requirements on the optical pump source. We investigate these requirements for an example x-ray laser (XRL) in Carbon lasing on the 2p-1s transition at 45 A. Competing with this lasing transition is the very fast Auger decay rate out of the upper lasing state, such that the x-ray laser would self-terminate on a femto- second time scale. XRL gain may be demonstrated if pump energy is delivered in a time short when compared to the Auger rate. The fast self-termination also demands that we sequentially pump the length of the x-ray laser at the group velocity of the x-ray laser. This is the classical traveling wave requirement. It imposes a condition on the pumping source that the phase angle of the pump laser be precisely de- coupled from the pulse front angle. At high light intensities, this must be performed with a vacuum grating delay line. We will also include a discussion of issues related to pump energy delivery, i.e. pulse-front curvature, temporal blurring and puke fidelity. An all- reflective optical system with low aberration is investigated to see if it fulfills the requirements. It is expected that these designs together with new high energy (>1J) ultra-short pulse (< 40 fs) pump lasers now under construction may fulfill our pump energy conditions and produce a tabletop x-ray laser.
Date: November 10, 1997
Creator: Snavely, R.A.; Da Silva, L.B.; Eder, D.C.; Matthews, D.L. & Moon, S.J.
Partner: UNT Libraries Government Documents Department

Performance of a diode-end-pumped Yb:YAG laser

Description: Using an end-pumped technology developed at LLNL we have demonstrated a Yb:YAG laser capable of delivering up to 434 W of CW power and 280 W of Q-switched power. In addition, we have frequency doubled the output to 515 nm using a dual crystal scheme to produce 76 W at 10 kHz in a 30 ns pulse length.
Date: May 5, 1997
Creator: Bibeau, C.; Beach, R.; Ebbers, C. & Emanuel, M.
Partner: UNT Libraries Government Documents Department

A 3-dimensional ray-trace model for predicting the performance of flashlamp-pumped laser amplifiers

Description: We have developed a fully three-dimensional model for the performance of flashlamp pumped laser amplifiers. The model uses a reverse ray-trace technique to calculate the pumping of the laser glass by the flashlamp radiation. We have discovered several different methods by which we can speed up the calculation of the gain profile in a amplifier. The model predicts the energy-storage performance of the Beamlet amplifiers to better than 5%. This model will be used in the optimization of the National Ignition Facility (NIF) amplifier design.
Date: February 13, 1997
Creator: Jancaitis, K.S.; Haney, S.W.; Munro, D.H.; Le Touze, G. & Cabourdin, O.
Partner: UNT Libraries Government Documents Department

Nuclear magnetic resonance imaging with hyper-polarized noble gases

Description: This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The nuclei of noble gases can be hyper polarized through a laser-driven spin exchange to a degree many orders of magnitude larger than that attainable by thermal polarization without requiring a strong magnetic field. The increased polarization from the laser pumping enables a good nuclear magnetic resonance (NMR) signal from a gas. The main goal of this project was to demonstrate diffusion-weighted imaging of such hyper-polarized noble gas with magnetic resonance imaging (MRI). Possible applications include characterizing porosity of materials and dynamically imaging pressure distributions in biological or acoustical systems.
Date: October 1, 1997
Creator: Schmidt, D.M.; George, J.S.; Penttila, S.I. & Caprihan, A.
Partner: UNT Libraries Government Documents Department

Modleing of psec laser driven Ne-like and Ni-like x-ray lasers

Description: This paper models recent experiments in which a solid titanium target was illuminated by several joules of combined energy from a nsec laser pulse to create a preplasma followed by a psec laser pulse to drive the gain. Gains greater than 200 cm{sup -1} are predicted for the Ne-like Ti 3p {sup 1}S{sub 0} {yields} 3s {sup 1}P{sub 1} transition at 32.6 nm which is driven by the monopole collisional excitation. High gain is also predicted for the 3d {sup 1}P{sub 1} {yields} 3p {sup 1}P{sub 1} transition at 30.1 nm which is driven by a combination of collisional excitation and self photopumping. We also discuss the possibilities for driving a Ne-like Ge laser using this approach. For the Ni-like ions we model a solid molybdenum target under similar conditions used for Ti and predict gains greater than 300 cm{sup -1} for the Ni-like Mo 4d {sup 1}S{sub 0} {yields} 4p {sup 1}P{sub 1} transition at 18.9 nm which is driven by the monopole collisional excitation. High gain is also predicted for a self photopumped 4f {sup 1}P{sub 1} {yields} 4d {sup 1}P{sub 1} transition at 22.0 nm and several other transitions driven by inner shell collisional ionization.
Date: June 1, 1997
Creator: Nilsen, J.
Partner: UNT Libraries Government Documents Department

Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials and organisms

Description: Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This dissertation is primarily concerned with the principles and practice of optically pumped nuclear magnetic resonance (OPNMR). The enormous sensitivity enhancement afforded by optical pumping noble gases can be exploited to permit a variety of novel NMR experiments across many disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, and zero-field NMR and MRI.
Date: December 1, 1999
Creator: Goodson, Boyd M.
Partner: UNT Libraries Government Documents Department

Broadly Turnable Pump-Resonant Diode-Pumped CW PPLN OPO

Description: We have observed low threshold operation of a broadly tunable (2.18-3.4 µm) pump-resonant cw periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO). When pumped at 806 nm with 410 mW from a custom-built diode laser the OPO generated 20 mW of idler output at 3.3 µm.
Date: April 29, 1999
Creator: Alford, W.J.; Bowers, Mark S.; Raymond, T.D. & Seamans, J.F.
Partner: UNT Libraries Government Documents Department

Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

Description: We discuss the upconversion luminescence efficiencies of phosphors that generate red, green, and blue light. The phosphors studied are single crystals and powders co-doped with Er{sup 3+} and Yb{sup 3+}, and with Tm{sup 3+} and Yb{sup 3+}. The Yb ions are pumped near 980 nm; transfers of two or three quanta to the co-doped rare earth ion generate visible luminescence. The main contribution embodied in this work is the quantitative measurement of this upconversion efficiency, based on the use of a calibrated integrating sphere, determination of the fraction of pump light absorbed, and careful control of the pump laser beam profile. The green phosphors are the most efficient, yielding efficiency values as high as 4 %, with the red and blue materials giving 1 - 2 %. Saturation was observed in all cases, suggesting that populations of upconversion steps of the ions are maximized at higher power. Quasi-CW modeling of the intensity- dependent upconversion efficiency was attempted; input data included level lifetimes, transition cross sections, and cross-relaxation rate coefficients. The saturation of the Yb,Er:fluoride media is explained as the pumping of Er{sup 3+} ions into a bottleneck (long-lived state)- the {sup 4}I{sub 13/2} metastable level, making them unavailable for further excitation transfer. 32 refs., 5 figs., 3 tabs.
Date: July 26, 1997
Creator: Page, R.H.; Schaffers, K.I.; Waide, P.A.; Tassano, J.B.; Payne, S.A.; Kruplce, W.F. et al.
Partner: UNT Libraries Government Documents Department

Recent advances and challenges for diode-pumped solid-state lasers as an inertial fusion energy driver candidate

Description: We discuss how solid-state laser technology can serve in the interests of fusion energy beyond the goals of the National Ignition Facility (NIF), which is now being constructed to ignite a deuterium-tritium target to fusion conditions in the laboratory for the first time. We think that advanced solid-state laser technology can offer the repetition-rate and efficiency needed to drive a fusion power plant, in contrast to the single-shot character of NIF. As discuss below, we propose that a gas-cooled, diode-pumped Yb:S-FAP laser can provide a new paradigm for fusion laser technology leading into the next century.
Date: December 23, 1997
Creator: Payne, S.A.; Beach, R.J. & Bibeau, C.
Partner: UNT Libraries Government Documents Department

Development of a prototype optical refrigerator

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have carried out a range of tasks directed toward the construction and testing of a proof-of-principle optical refrigerator prototype. They procured and tested new cooling elements that are at the heart of an optical refrigerator. The cooling element absorbs pump radiation and then fluoresces with nearly unity quantum efficiency. They constructed and tested a cooling chamber with low thermal emissivity walls that reduces the parasitic heating.
Date: January 1, 1998
Creator: Epstein, R.I.; Edwards, B.C. & Sigel, G.H.
Partner: UNT Libraries Government Documents Department

Informal Workshop on Intense Polarized Ion Sources : a Summary

Description: An Informal Workshop on Intense Polarized Ion Sources was held on March 6, 1980, at the O'Hare Hilton Hotel, Chicago, Illinois. The purpose of the Workshop was to discuss problems in developing higher-intensity polarized proton sources, particularly the optically-pumped source recently proposed by L.W. Anderson of the University of Wisconsin. A summary of the discussions is reported. The main topic was the concept of utilizing an optically-pumped alkali vapor described by L. W. Anderson of the University of Wisconsin (Nucl. Instrum. Methods. v.167, pp. 369, 1979) and the questions he raised in that paper. The workshop started with a talk by Professor Anderson in which he further described the concepts of his paper and suggested some topics he felt needed further investigation. Later in the day, the discussion switched to other possible high-intensity polarized sources, in particular with the H/Cs charge exchange source similar to the system operating at the University of Wisconsin.
Date: March 1980
Creator: Schultz, Peter F.
Partner: UNT Libraries Government Documents Department

Continuous-wave diode-pumped Cr:YAG laser

Description: We describe a diode-pumped Cr{sup 4+}:YAG laser operating at 1.45 {mu}m. The laser outputs xxx mW when pumped by a 2 W single-transverse-mode 980 nm InGaAs diode.
Date: July 1, 1995
Creator: Carrig, T.J.; Cockroft, N.J.; Pollock, C.R. & Walpole, J.N.
Partner: UNT Libraries Government Documents Department

Coupled Resonator Vertical Cavity Laser Diodes

Description: For many applications, the device performance of edge emitting semiconductor lasers can be significantly improved through the use of multiple section devices. For example, cleaved coupled cavity (C3) lasers have been shown to provide single mode operation, wavelength tuning, high speed switching, as well as the generation of short pulses via mode-locking and Q-switching [1]. Using composite resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the coupling between the monolithic cavities, incorporate passive or active resonators which are spectrally degenerate or detuned, and to fabricate these devices in 2-dimensional arrays. Composite resonator vertical cavity lasers (CRVCL) have been examined using optical pumping and electrical injection [2-5]. We report on CRVCL diodes and show that efficient modulation of the laser emission can be achieved by either forward or reverse biasing the passive cavity within a CRVCL.
Date: July 22, 1999
Creator: Choquette, K.D.; Chow, W.W.; Fischer, A.J.; Allerman, A.A.; Hou, H.Q. & Geib, K.M.
Partner: UNT Libraries Government Documents Department

Applications of microlens-conditioned laser diode arrays

Description: The ability to condition the radiance of laser diodes using shaped-fiber cylindrical-microlens technology has dramatically increased the number of applications that can be practically engaged by diode laser arrays. Lawrence Livermore National Laboratory (LLNL) has actively pursued optical efficiency and engineering improvements in this technology in an effort to supply large radiance-conditioned laser diode array sources for its own internal programs. This effort has centered on the development of a modular integrated laser diode packaging technology with the goal of enabling the simple and flexible construction of high average power, high density, two-dimensional arrays with integrated cylindrical microlenses. Within LLNL, the principal applications of microlens-conditioned laser diode arrays are as high intensity pump sources for diode pumped solid state lasers (DPSSLs). A simple end-pumping architecture has been developed and demonstrated that allows the radiation from microlens-conditioned, two-dimensional diode array apertures to be efficiently delivered to the end of rod lasers. To date, pump powers as high as 2.5 kW have been delivered to 3 mm diameter laser rods. Such high power levels are critical for pumping solid state lasers in which the terminal laser level is a Stark level lying in the ground state manifold. Previously, such systems have often required operation of the solid state gain medium at low temperature to freeze out the terminal laser Stark level population. The authors recently developed high intensity pump sources overcome this difficulty by effectively pumping to much higher inversion levels, allowing efficient operation at or near room temperature. Because the end-pumping technology is scalable in absolute power, the number of rare-earth ions and transitions that can be effectively accessed for use in practical DPSSL systems has grown tremendously.
Date: January 1, 1995
Creator: Beach, R.J.; Emanuel, M.A. & Freitas, B.L.
Partner: UNT Libraries Government Documents Department