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High-average-power diode-pumped Yb: YAG lasers

Description: A scaleable diode end-pumping technology for high-average-power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M{sup 2} = 2.4) q-switched operation has also been demonstrated at over 180 W of average output power. More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M{sup 2} value of 13.5 at an optical-to-optical conversion efficiency of 27.5%. With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M{sup 2} < 2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes. (2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods.
Date: October 1, 1999
Creator: Avizonis, P V; Beach, R; Bibeau, C M; Emanuel, M A; Harris, D G; Honea, E C et al.
Partner: UNT Libraries Government Documents Department

Next-generation laser for Inertial Confinement Fusion

Description: We report on the progress in developing and building the Mercury laser system as the first in a series of a new generation of diode- pumped solid-state Inertial Confinement Fusion (ICF) lasers at Lawrence Livermore National Laboratory (LLNL). Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1 omega energies of 100 J and with 2 omega/3 omega frequency conversion.
Date: September 29, 1997
Creator: Marshall, C.D.; Deach, R.J. & Bibeau, C.
Partner: UNT Libraries Government Documents Department

Optimized, diode pumped, Nd:glass, prototype regenerative amplifier for the National Ignition Facility (NIF)

Description: The National Ignition Facility (NIF) will house a 2 MJ Nd:glass laser system to be used for a broad range of inertial confinement fusion experiments. This record high energy laser output will be initiated by a single low energy, fiber -based master oscillator which will be appropriately shaped in time and frequency prior to being split into 48 beams for intermediate amplification. These 48 intermediate energy beams will feed the 192 main amplifier chains. We report on the baseline design and test results for an amplifier subsystem in the intermediate amplifiers. The subsystem is based on a diode pumped, Nd:glass regenerative amplifier. The amplifier is comprised fo a linear, folded, TEM{sub 00}, 4.5m long cavity and represents the highest gain (approximately 10{sup 7}) component in the NIF laser system. Two fundamentally important requirements for this amplifier include output energy of 20 mJ and square pulse distortion of less than 1.45. With a single 48 bar 4.5kW peak power diode array and lens duct assembly we pump a 5 mm diameter X 50 mm long Nd-doped, phosphate glass rod, and amplify the mode matched, temporally shaped (approximately 20ns in duration)oscillator seed pulse to 25 mJof output energy with a very acceptable square pulse distortion of 1.44. This most recent design of the regenerative amplifier has increased the performance and reduced the cost, enabling it to become a solid baseline for the NIF laser system.
Date: December 1, 1997
Creator: Martinez, M.; Crane, J.; Penko, F. & Browning, D.
Partner: UNT Libraries Government Documents Department

CW and Q-switched performance of a diode end-pumped Yb:YAG laser. Revision 1

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 226 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: February 19, 1997
Creator: Bibeau, C.; Beach, R.; Ebbers, C.; Emanuel, M. & Skidmore, J.
Partner: UNT Libraries Government Documents Department

Simple numerical models for antiproton-hydrogen scattering

Description: A diode-side-pumped discrete-optic E{sup 3+}:YAG laser employs pump-light coupling through a sapphire plate diffusion-bonded to the laser slab, giving reduced thermal lensing and exceptional beam quality (M{sup 2} {approx} 1.3.) The novel architecture is also applicable to other side-pumped lasers.
Date: August 23, 1996
Creator: Morgan Jr., D. L., LLNL
Partner: UNT Libraries Government Documents Department

A diode-pumped channel waveguide laser fabricated in Nd: phosphate glass

Description: We report on the laser performance of a Nd:phosphate glass (Nd:IOG-1) channel waveguide laser fabricated by electric field assisted Ag{sup +} diffusion. Lasing was achieved in two different size channels, 29 x 9 {micro}m{sup 2} and 50 x 9 {micro}m{sup 2}, on a sample of length 8 mm. Slope efficiencies of {approximately} 15% with respect to incident pump power were measured. Losses in the 29 um wide channel were measured to be in the range 0.2--1.1 dB/cm and in the 50 mm channel, 0.2--0.4 dB/cm. The laser spectrum, centered about the emission peak of 1053 nm, was multimode and randomly polarized.
Date: January 29, 1999
Creator: Patel, F D; Honea, E C; Krol, D; Payne, S A & Hayden, J
Partner: UNT Libraries Government Documents Department

Diode-Pumped Mode-Locked LiSAF Laser

Description: Under this contract we have developed Cr{sup 3+}:LiSrAlF{sub 6} (Cr:LiSAF, LiSAF) mode-locked lasers suitable for generation of polarized electrons for CEBAF. As 670 nm is an excellent wavelength for optical pumping of Cr:LiSAF, we have used a LIGHTWAVE developed 670 nm diode pump module that combines the output of ten diode lasers and yields approximately 2 Watts of optical power. By the use of a diffraction limited pump beam however, it is possible to maintain a small mode size through the length of the crystal and hence extract more power from Cr:LiSAF laser. For this purpose we have developed a 1 Watt, red 660nm laser (LIGHTWAVE model 240R) which serves as an ideal pump for Cr:LiSAF and is a potential replacement of costly and less robust krypton laser. This new system is to compliment LIGHTWAVE Series 240, and is currently being considered for commercialization. Partially developed under this contract is LIGHTWAVEs product model 240 which has already been in our production lines for a few months and is commercially available. This laser produces 2 Watts of output at 532 nm using some of the same technology developed for production of the 660nm red system. It is a potential replacement for argon ion lasers and has better current and cooling requirements and is an excellent pump source for Ti:Al{sub 2}O{sub 3}. Also, as a direct result of this contract we now have the capability of commercially developing a mode-locked 100MHz Cr:LiSAF system. Such a laser could be added to our 100 MHz LIGHTWAVE Series 131. The Series 131 lasers provide pico second pulses and were originally developed under another DOE SBIR. Both models of LIGHTWAVE Series 240 lasers, the fiber coupled pump module and the 100MHz LiSAF laser of Series 131 have been partially developed under this contract, and are commercially ...
Date: February 1, 1996
Partner: UNT Libraries Government Documents Department

Performance results of the high gain, Nd: glass, engineering prototype preamplifier module (PAM) for the National Ignition Facility (NIF)

Description: We describe recent, energetics performance results on the engineering preamplifier module (PAM) prototype located in the front end of the 1.8MJ National Ignition Facility (NIF) laser system. Three vertically mounted subsystem located in the PAM provide laser gain as well as spatial beam shaping. The first subsystem in the PAM prototype is a diode pumped, Nd:glass, linear, TEM{sub 00}, 4.5m long regenerative amplifier cavity. With a single diode pumped head, we amplify a 1nJ, mode matched, temporally shaped ({approx} 20ns) seed pulse by a factor of approximately 10{sup 7} to 20mJ. The second subsystem in the PAM is the beam shaping module, which magnifies the gaussian output beam of the regenerative amplifier to provide a 30mm x 30mm square beam that is spatially shaped in two dimensions to pre-compensate for radial gain profiles in the main amplifiers. The final subsystem in the PAM is the 4-pass amplifier which relay images the 1mJ output of the beam shaper through four gain passes in a {phi}5cm x 48cm flashlamp pumped rod amplifier, amplifying the energy to 175. The system gain of the PAM is 10{sup 10}. Each PAM provides 35 of injected energy to four separate main amplifier chains which in turn delivers 1.8MJ in 192 frequency converted laser beams to the target for a broad range of laser fusion experiments.
Date: February 9, 1999
Creator: Braucht, J.; Browning, D.; Crane, J. K.; Crawford, J.; Deadrick, F. J.; Hawkins, S. et al.
Partner: UNT Libraries Government Documents Department

FY2005 Progress Summary and FY2006 Program Plan Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers, and Complementary Technologies, for Applications in Energy and Defense

Description: The primary focus this year was to operate the system with two amplifiers populated with and pumped by eight high power diode arrays. The system was operated for extended run periods which enabled average power testing of components, diagnostics, and controls. These tests were highly successful, with a demonstrated energy level of over 55 joules for 4 cumulative hours at a repetition rate of 10 Hz (average power 0.55 kW). In addition, high average power second harmonic generation was demonstrated, achieving 227 W of 523.5 nm light (22.7 J, 10 Hz, 15 ns, 30 minutes) Plans to achieve higher energy levels and average powers are in progress. The dual amplifier system utilizes a 4-pass optical arrangement. The Yb:S-FAP slabs were mounted in aerodynamic aluminum vane structures to allow turbulent helium gas flow across the faces. Diagnostic packages that monitored beam performance were deployed during operation. The laser experiments involved injecting a seed beam from the front end into the system and making four passes through both amplifiers. Beam performance diagnostics monitored the beam on each pass to assess system parameters such as gain and nearfield intensity profiles. This year, an active mirror and wavefront sensor were procured and demonstrated in an off-line facility. The active mirror technology can correct for low order phase distortions at user specified operating conditions (such as repetition rates different than 10 Hz) and is a complementary technology to the static phase plates used in the system for higher order distortions. A picture of the laser system with amplifier No.2 (foreground) and amplifier No.1 (background) is shown in Fig. 1.0.1.1. The control system and diagnostics were recently enhanced for faster processing and allow remote operation of the system. The growth and fabrication of the Yb:S-FAP slabs constituted another major element of our program objectives. Our goal ...
Date: March 24, 2006
Creator: Ebbers, C
Partner: UNT Libraries Government Documents Department

Test results for 320 nm and 390 nm remote sensing sources using a 150 mJ, 100 Hz repetition rate, injection-seeded diode-pumped Nd:YAG slab-laser developed by Coherent Technologies, Inc.

Description: This report describes results of tests using a laser system designed by Coherent Technologies, Inc., in conjunction with Sandia developed nonlinear optics technology. Test results are described for three different optical parametric oscillators built at Sandia. The report concludes with recommendations for future work.
Date: July 1, 2005
Creator: Armstrong, Darrell Jewell
Partner: UNT Libraries Government Documents Department

Development of All-Solid-State Sensors for Measurement of Nitric Oxide and Ammonia Concentrations by Optical Absorption in Particle-Laden Combustion Exhaust Streams

Description: An all-solid-state continuous-wave (cw) laser system for ultraviolet absorption measurements of the nitric oxide (NO) molecule has been developed and demonstrated. For the NO sensor, 250 nW of tunable cw ultraviolet radiation is produced by sum-frequency-mixing of 532-nm radiation from a diode-pumped Nd:YAG laser and tunable 395-nm radiation from an external cavity diode laser (ECDL). The sum-frequency-mixing process occurs in a beta-barium borate crystal. The nitric oxide absorption measurements are performed by tuning the ECDL and scanning the sum-frequency-mixed radiation over strong nitric oxide absorption lines near 226 nm. In Year 1 of the research, the nitric oxide sensor was used for measurements in the exhaust of a coal-fired laboratory combustion facility. The Texas A&M University boiler burner facility is a 30 kW (100,000 Btu/hr) downward-fired furnace with a steel shell encasing ceramic insulation. Measurements of nitric oxide concentration in the exhaust stream were performed after modification of the facility for laser based NOx diagnostics. The diode-laser-based ultraviolet absorption measurements were successful even when the beam was severely attenuated by particulate in the exhaust stream and window fouling. Single-laser-sweep measurements were demonstrated with an effective time resolution of 100 msec, limited at this time by the scan rate of our mechanically tuned ECDL system. In Year 2, the Toptica ECDL in the original system was replaced with a Sacher Lasers ECDL. The mode-hop-free tuning range and tuning rate of the Toptica ECDL were 25 GHz and a few Hz, respectively. The mode-hop-free tuning range and tuning rate of the Sacher Lasers ECDL were 90 GHz and a few hundred Hz, respectively. The Sacher Lasers ECDL thus allows us to scan over the entire NO absorption line and to determine the absorption baseline with increased accuracy and precision. The increased tuning rate is an advantage in that data can be acquired ...
Date: September 30, 2005
Creator: Caton, Jerald A.; Annamalai, Kalyan & Lucht, Robert P.
Partner: UNT Libraries Government Documents Department

Laser diagnostic for high current H{sup {minus}} beams

Description: In the last 5 years, significant technology advances have been made in the performance, size, and cost of solid-state diode-pumped lasers. These developments enable the use of compact Q-switched Nd:YAG lasers as a beam diagnostic for high current H{sup {minus}} beams. Because the threshold for photodetachment is only 0.75 eV, and the maximum detachment cross section is 4 {times} 10{sup {minus}17} cm{sup 2} at 1.5 eV, a 50 mJ/pulse Q-switched Nd:YAG laser can neutralize a significant fraction of the beam in a single 10-ns wide pulse. The neutral beam maintains nearly identical parameters as the parent H{sup {minus}} beam, including size, divergence, energy, energy spread, and phase spread. A dipole magnet can separate the neutral beam from the H{sup {minus}} beam to allow diagnostics on the neutral beam without intercepting the high-current H{sup {minus}} beam. Such a laser system can also be used to extract a low current proton beam, or to induce fluorescence in partially stripped heavy ion beams. Possible beamline diagnostic systems will be reviewed, and the neutral beam yields will be calculated.
Date: May 5, 1998
Creator: Shafer, R.E.
Partner: UNT Libraries Government Documents Department

Analysis of Sr{sub 5{minus}x}Ba{sub x}(PO{sub 4}){sub 3}F:Yb{sup 3+} crystals for improved laser performance with diode-pumping

Description: Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 < x < 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb{sup 3+}:S-FAP [Yb{sup 3+}: Sr{sub 5}(PO{sub 4}){sub 3}F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-arrays have a FWHM pump band of >5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increases the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping.
Date: February 19, 1997
Creator: Schaffers, K.I.; Bayramian, A.J.; Marshall, C.D.; Tassano, J.B. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

Radiation damage and waste management options for the SOMBRERO final focus system and neutron dumps

Description: Previous studies of the safety and environmental aspects of the SOMBRERO inertial fusion energy (IFE) power plant design did not completely address the issues associated with the final focus system. While past work calculated neutron fluences for a grazing incidence metal mirror (GIMM) and a final focus mirror, scattering off of the final optical component was not included, and thus, fluences in the final focus mirror were significantly underestimated. In addition, past work did not consider neutron-induced gamma-rays. Finally, power plant lifetime waste volumes may have been underestimated as neutron activation of the neutron dumps and building structure were not addressed. In the present work, a modified version of the SOMBRERO target building is presented where a significantly larger open solid-angle fraction (5%) is used to enhance beam smoothing of a diode-pumped solid-state laser (DPSSL). The GIMMs are replaced with transmissive fused silica wedges and have been included in three -dimensional neutron and photon transport calculations. This work shows that a power plant with a large open solid-angle fraction, needed for beam smoothing with a DPSSL, is acceptable from tritium breeding, and neutron activation points-of-view.
Date: August 9, 1999
Creator: Latkowski, J F; Meier, W R & Reyes, S
Partner: UNT Libraries Government Documents Department

Progress and critical issues for IFE blanket and chamber research

Description: Advances in high gain target designs for Inertial Fusion Energy (IFE), and the initiation of construction of large megajoule-class laser facilities in the U.S. (National Ignition Facility) and France (Laser-Megajoule) capable of testing the requirements for inertial fusion ignition and propagating burn, have improved the prospects for IFE. Accordingly, there have recently been modest increases in the US fusion research program related to the feasibility of IFE. These research areas include heavy-ion accelerators, Krypton-Fluoride (KrF) gas lasers, diode-pumped, solid-state (DPSSL) lasers, IFE target designs for higher gains, feasibility of low cost IFE target fabrication and accurate injection, and long-lasting IFE fusion chambers and final optics. Since several studies of conceptual IFE power plant and driver designs were completed in 1992-1996 [1-5], U.S. research in the IFE blanket, chamber, and target technology areas has focused on the critical issues relating to the feasibility of IFE concepts towards the goal of achieving economically-competitive and environmentally-attractive fusion energy. This paper discusses the critical issues in these areas, and the approaches taken to address these issues. The U.S. research in these areas, called IFE Chamber and Target Technologies, is coordinated through the Virtual Laboratory for Technology (VLT) formed by the Department of Energy in December 1998.
Date: June 23, 1999
Creator: Abdou, M.; Kulcinski, G.L.; Latkowski, J.F.; Logan, B.G.; Meier, W.R.; Moir, R.W. et al.
Partner: UNT Libraries Government Documents Department

Aluminum-Free Semiconductors and Packaging

Description: The use of laser diodes instead of flashlamps to pump solid state lasers generally results in lighter weight, more compact systems with improved efficiency and reliability. These traits are important to a wide variety of applications in military, industrial and other areas. Common solid state laser systems such as yttrium aluminum garnet doped with neodymium or ytterbium (Nd:YAG and Yb:YAG, respectively) require pump light in the 800 to 1000 nm range, and such laser diodes have typically been fabricated in the AlGaAs material system on a GaAs substrate. Unfortunately, the presence of aluminum in or near the light-generating regions of these devices appears to limit their high-power performance, so for improved performance attention has turned to the aluminum-free (''Al-free'') material system of InGaAsP on a GaAs substrate. Laser diodes in this system offer the wavelength coverage similar to the AlGaAs/GaAs material system, and early results suggest that they may offer improved high-power performance. However, such Al-free diodes are more challenging to manufacture than AlGaAs-based devices. The goal of this LDRD project has been to evaluate Al-free diode technology in comparison with conventional AlGaAs-based structures for use in diode-pumped solid state lasers. This has been done by testing commercially available devices, surveying the literature, developing in-house capability in order to explore new device designs, and by engaging a leading university research group in the field.
Date: February 3, 2000
Creator: Emanuel, M.A.
Partner: UNT Libraries Government Documents Department