Effect of Mixing on HF Overtone Laser Efficiency
L. H. Sentman,* A. Eyre, J. Cassibry, B. Wootton
Shafer Corp.

To investigate the role of mixing on HF overtone laser efficiency, a new nozzle, which injects the helium and hydrogen through orifices in the side wall of the supersonic portion of the nozzle, was designed and constructed. The fundamental performance of this nozzle is twice that of the parallel slit nozzle. For identical saturation levels, the overtone efficiency is the same as that of the parallel slit nozzle. Mixing does not affect HF overtone laser efficiency.

Line Selected Oscillator Performance
L. H. Sentman,* J. Cassibry, A. J. Eyre, B. Wootton
Shafer Corp.

A diffraction grating was used in the Littrow and off-Littrow configurations to select the lines in a cw HF stable resonator. The beam is outcoupled through a partially reflective mirror. Single-line Littrow, single-line off-Littrow, and off-Littrow line pair performance were measured. For the first time, as far as we know, in the operation of chemical lasers, Littrow and off-Littrow lines lased simultaneously. Two-line (one Littrow line, one off-Littrow line) and three-line (one Littrow line, two off-Littrow lines) Littrow/off-Littrow line combinations were demonstrated. The grating reflectivity was a strong function of the polarization of the laser beam. Data indicated that the grating generated a beam whose polarization was perpendicular to the grating grooves.

HF Nozzle Technology
L. H. Sentman,* B. Wootton, A. Eyre, J. Cassibry
Schafer Corp.

Several concepts for improving the performance of HF laser nozzles are under investigation.

Large-Scale CFD for Supersonic Systems
L. H. Sentman,* W. C. Solomon,* D. L. Carroll,* M. Sotano, T. Madden
Defense Advanced Research Projects Agency; Logican; Aerosoft

DARPA and the U.S. Air Force are sponsoring large-scale computational research for parallel computation. Large-scale 3-D reacting flow models are developed to support advanced laser research at Phillips Lab and air-breathing propulsion research underway at the Air Force Propulsion Lab.

High-Energy Laser Systems Technology
L. H. Sentman,* W. C. Solomon, D. Carroll, D. King
U.S. Air Force Phillips Laboratory; STI Optronics; TRW, Inc.

This work involves research into the establishment and operation of a large-scale COIL laser for commercial applications. A new laboratory is being constructed for establishing a commercial technology for high-energy lasers. The initial project is the development of a prototype system to be used in laser processing of metals. This problem involves the development of a new laser technology, demonstration at a scaleable power level, and materials processing of lasers operating near 1 micrometer wavelength. Initial operation of the system demonstrated a kilowatt at 25% chemical efficiency.

Large-Scale Simulations of Chemical Lasers
W. C. Solomon,* D. Stromberg, L. Fockler
Aerosoft Corp.; Defense Advanced Research Projects Agency

Large 3-D simulations of chemical laser flowfields are being conducted to determine the most efficient configurations of hardware and software for the next generation of computing. Verification of experimental data and earlier, less complex computations is complete, and the system performance is being assessed. The work is being conducted using the reacting flow model provided by the GASP CFD simulation on a variety of parallel and high-speed processors.

An Experimental Investigation of the COIL Laser
W. C. Solomon,* L. H. Sentman,* D. L. Carroll,* D. King
STI Optronics; U.S. Air Force Research Laboratory, AF 95111

A subscale model of an advanced chemical laser is operating to provide information on the proper design of a full-scale device. Designs taken from the DARPA effort are being incorporated into the experiment. A series of experiments focusing on potential DOD applications as well as on a database for the commercial development of the technology are underway. This is providing basic understanding of the technology, a useful database for the CFD modeler, and a highly flexible testbed to pursue new approaches to find more efficiency as well as better quality beams and delivery systems.