Lethality Effects of a High-Power Solid-State Laser

We study the material interactions of a 25-kW solid-state laser, in experiments characterized by relatively large spot size sizes ({approx}3 cm) and the presence of airflow. The targets are 1-cm slabs of iron or aluminum. In the experiments with iron, we show that combustion plays an important role in heating the material. In the experiments with aluminum, there is a narrow range of intensities within which the material interactions vary from no melting at all to complete melt-through. A paint layer serves to increase the absorption. We explain these effects and incorporate them into a comprehensive computational model

Laser-Material Interaction Studies Utilizing the Solid-State Heat Capacity Laser

A variety of laser-material interaction experiments have been conducted at Lawrence Livermore National Laboratory (LLNL) utilizing the solid-state heat capacity laser (SSHCL). For these series of experiments, laser output power is 25kW, on-target laser spot sizes of up to 16 cm by 16 cm square, with air speeds of approximately 100 meters per second flowing across the laser-target interaction surface as shown in Figure 1. The empirical results obtained are used to validate our simulation models

The Use of Large Transparent Ceramics in a High Powered, Diode Pumped Solid State Laser

The advent of large transparent ceramics is one of the key enabling technological advances that have shown that the development of very high average power compact solid state lasers is achievable. Large ceramic neodymium doped yttrium aluminum garnet (Nd:YAG) amplifier slabs are used in Lawrence Livermore National Laboratory's (LLNL) Solid State Heat Capacity Laser (SSHCL), which has achieved world record average output powers in excess of 67 kilowatts. We will describe the attributes of using large transparent ceramics, our present system architecture and corresponding performance; as well as describe our near term future plans

DEVELOPMENT OF ADAPTIVE RESONATOR TECHNIQUES FOR HIGH-POWER LASERS

The design of an adaptive wavefront control system for a high-power Nd:Glass laser will be presented. Features of this system include: an unstable resonator in confocal configuration, a multi-module slab amplifier, and real-time intracavity adaptive phase control using deformable mirrors and high-speed wavefront sensors. Experimental results demonstrate the adaptive correction of an aberrated passive resonator (no gain)

Technical challenges for the future of high energy lasers

The Solid-State, Heat-Capacity Laser (SSHCL) program at Lawrence Livermore National Laboratory is a multi-generation laser development effort scalable to the megawatt power levels with current performance approaching 100 kilowatts. This program is one of many designed to harness the power of lasers for use as directed energy weapons. There are many hurdles common to all of these programs that must be overcome to make the technology viable. There will be a in-depth discussion of the general issues facing state-of-the-art high energy lasers and paths to their resolution. Despite the relative simplicity of the SSHCL design, many challenges have been uncovered in the implementation of this particular system. An overview of these and their resolution are discussed. The overall system design of the SSHCL, technological strengths and weaknesses, and most recent experimental results will be presented

Plasma Electrode Pockels Cell for the National Ignition Facility

The National Ignition Facility (NIF), now under construction at Lawrence Livermore National Laboratory, will be the largest laser fusion facility ever built. The NIF laser architecture is based on a multi-pass power amplifier to reduce cost and maximize performance. A key component in this laser design is an optical switch that closes to trap the optical pulse in the cavity for four gain passes and then opens to divert the optical pulse out of the amplifier cavity. The switch is comprised of a Pockels cell and a polarizer and is unique because it handles a beam that is 40 cm x 40 cm square and allows close horizontal and vertical beam spacing. Conventional Pockels cells do not scale to such large apertures or the square shape required for close packing. Our switch is based on a Plasma-Electrode Pockels Cell (PEPC). In a PEPC, low-pressure helium discharges (l-2 kA) are formed on both sides of a thin slab of electro-optic material. Typically, we use KH2P04 crystals (KDP). The discharges form highly conductive, transparent sheets that allow uniform application of a high-voltage pulse (17 kV) across the crystal. A 37 cm x 37 cm PEPC has been in routine operation for two years on the 6 W Beamlet laser at LLNL. For the NIF, a module four apertures high by one wide (4x1) is required. However, this 4x1 mechanical module will be comprised electrically of a pair of 2x1 sub-modules. Last year (FY 97), we demonstrated full operation of a prototype 2x I PEPC. In this PEPC, the plasma spans two KDP crystals. A major advance in the 2x1 PEPC ovel the Beamlet PEPC is the use of anodized aluminum construction that still provides sufficient insulation to allow formation of the planar plasmas. In this paper, we discuss full 4x1 NIF prototypes

Plasma electrode pockels cell for the National Ignition Facility

The National Ignition Facility (NIF), now under construction at Lawrence Livermore National Laboratory, will be the largest laser fusion facility ever built. The NIF laser architecture is based on a multi-pass power amplifier to reduce cost and maximize performance. A key component in this laser design is an optical switch that closes to trap the optical pulse in the cavity for four gain passes and then opens to divert the optical pulse out of the amplifier cavity. The switch is comprised of a Pockels cell and a polarizer and is unique because it handles a beam that is 40 cm x 40 cm square and allows close horizontal and vertical beam spacing. Conventional Pockels cells do not scale to such large apertures or the square shape required for close packing. Our switch is based on a Plasma-Electrode Pockels Cell (PEPC). In a PEPC, low-pressure helium discharges (l-2 kA) are formed on both sides of a thin slab of electro-optic material. Typically, we use KH2P04 crystals (KDP). The discharges form highly conductive, transparent sheets that allow uniform application of a high-voltage pulse (17 kV) across the crystal. A 37 cm x 37 cm PEPC has been in routine operation for two years on the 6 W Beamlet laser at LLNL. For the NIF, a module four apertures high by one wide (4x1) is required. However, this 4x1 mechanical module will be comprised electrically of a pair of 2x1 sub-modules. Last year (FY 97), we demonstrated full operation of a prototype 2x I PEPC. In this PEPC, the plasma spans two KDP crystals. A major advance in the 2x1 PEPC ovel the Beamlet PEPC is the use of anodized aluminum construction that still provides sufficient insulation to allow formation of the planar plasmas. In this paper, we discuss full 4x1 NIF prototypes

A Directed Energy System for Defeat of Improvised Explosive Devices and Landmines

We describe a laser system, built in our laboratory at LLNL, that has near-term, effective applications in exposing and neutralizing improvised explosive devices and landmines. We discuss experiments with this laser, demonstrating excavation capabilities and relevant material interactions. Model results are also described

Sub-50 femtosecond, multiterwatt Ti:sapphire laser system

We discuss a Ti:sapphire laser system based on chirped pulse amplification which produces over 750 mJ in sub-50 femtosecond pulses. We also describe a novel, all-reflective stretcher with a stretching ratio of 30,000

Plasma electrode pockels cell for the National Ignition Facility

The National Ignition Facility (NIF), now under construction at Lawrence Livermore National Laboratory, will be the largest laser fusion facility ever built. The NIF laser architecture is based on a multi-pass power amplifier to reduce cost and maximize performance. A key component in this laser design is an optical switch that closes to trap the optical pulse in the cavity for four gain passes and then opens to divert the optical pulse out of the amplifier cavity. The switch is comprised of a Pockels cell and a polarizer and is unique because it handles a beam that is 40 cm x 40 cm square and allows close horizontal and vertical beam spacing. Conventional Pockels cells do not scale to such large apertures or the square shape required for close packing. Our switch is based on a Plasma-Electrode Pockels Cell (PEPC). In a PEPC, low-pressure helium discharges (1-2 kA) are formed on both sides of a thin slab of electro-optic material. Typically, we use KH{sub 2}PO{sub 4 } crystals (KDP). The discharges form highly conductive, transparent sheets that allow uniform application of a high-voltage pulse (17 kV) across the crystal. A 37 cm x 37 cm PEPC has been in routine operation for two years on the 6 k.J Beamlet laser at LLNL. For the NIF, a module four apertures high by one wide (4x1) is required. However, this 4x1 mechanical module will be comprised electrically of a pair of 2x1 sub-modules. Last year (FY 97), we demonstrated full operation of a prototype 2x1 PEPC. In this PEPC, the plasma spans two KDP crystals. A major advance in the 2x1 PEPC over the Beamlet PEPC is the use of anodized aluminum construction that still provides sufficient insulation to allow formation of the planar plasmas