Keith A. Truesdell

A simplified analytic model for gain saturation and power extraction in the flowing chemical oxygen-iodine laser

This paper describes the development of a simplified saturation model (SSM) for predicting power extraction from a chemical oxygen-iodine laser (COIL). Using the Fabry-Perot gain saturation assumption, analytic expressions for COIL extraction efficiency are presented for both constant-density and variable-density cavity conditions. The model treats mirror scattering, nonsaturable distributed losses, and diffractive losses from the mode-limiting aperture and is shown to be in excellent agreement with experimental COIL power extraction data. A comparison of the model with the Rigrod power extraction model is presented showing that the Rigrod model accurately predicts COIL extraction efficiency only in the limit that the COIL device no longer behaves as a transfer laser.

Phillips Laboratory COIL technology overview

The basic technology and performance of the chemically pumped oxygen-iodine laser is reviewed. The performance is discussed in terms of the operation of the chemical oxygen generator, the kinetics of energy transfer from oxygen to iodine, and the extraction of power by the optical resonator. Techniques for generation of excited oxygen and iodine are reviewed. In addition advanced concepts for switching the laser on and off, switching the polarization, and frequency shifting are discussed.

High-efficiency operation of a 5-cm gain length supersonic chemical oxygen-iodine laser

The Air Force Phillips Laboratory has developed a small-scale supersonic Chemical Oxygen- Iodine Laser (COIL) test stand (VertiCOIL) in order to acquire COIL performance data quickly and inexpensively. The VertiCOIL device has demonstrated a chemical efficiency of 26.7%, the highest efficiency ever reported for a supersonic COIL. VertiCOIL uses a continuously-cooled basic hydrogen peroxide flowing loop which allows run times of greater than one hour.

Iodine dissociation in chemical oxygen-iodine lasers (COILs)

Iodine dissociation has been measured in the supersonic cavity of a chemical oxygen-iodine laser during lasing under a wide variety of flow conditions. By varying flow conditions, measured dissociations from 0 to 100 percent were observed. A simple model of the initial step in the dissociation process was developed that adequately rationalizes the measurements.

Chemical oxygen-iodine laser (COIL)

This is a review of tl Chemical Oxygen - Iodine Laser (COIL) technology, paying particular attention to historical perspectives in terms of highlighting the unique characteristics of COIL that have allowed it to develop into a high efficiency and a very forgiving system. Chemical pumping of lasing transitions has been around for a long time (HCI Lasers in 1965 and HF/DF Lasers in 1972), but most of the reaction energy ends up as heat in the lasing medium, generating the associated system engineering difficulties. COIL, on the other hand, has a very high efficiency in converting reaction energy to electronic excitation, and that fraction of the reaction energy which is released as heat does not end up in the laser cavity, but remains in the oxygen generator. This has tremendous engineering advantages for high efficiency systems.

Compact cw supersonic chemical oxygen-iodine laser (COIL)

A closed-loop flowing basic hydrogen peroxide (BHP) system with real-time cooling was constructed and coupled to a supersonic COIL, resulting in a 20-min. continuous run at an average power of 500 W. An overall BHP heat transfer coefficient of 150 BTU/(hr(DOT)ft2(DOT) degree(s)F) was measured.

History of chemical oxygen-iodine laser (COIL) development in the USA

This is an overview of the development of Chemical Oxygen-Iodine Laser (COIL) technology in the United States. Key technical developments will be reviewed, beginning in 1960 and culminating in 1977 with the first COIL lasing demonstration at the Air Force Weapons Laboratory (now the Phillips Laboratory). The discussion will then turn to subsonic laser development, supersonic lasing demonstration and efficiency improvements, and finishing with a brief discussion of some spin off COIL technologies. Particular emphasis will be placed on how the O2 (1(Delta) ) generator and O2-I2 mixing nozzle technologies evolved.

COIL performance modeling and recent advances in diagnostic measurements

This paper describes the analysis of power extraction from a chemical oxygen iodine laser (COIL) using a simplified saturation model (SSM). Previously our COIL modeling efforts have been limited by an inability to accurately measure O2(1(Delta) ) concentrations which in turn is a measure of the power available in the laser. Earlier application of the SSM to RotoCOIL data implied that our measured O2(1(Delta) ) could not be correct. In this paper we show how a new method for experimentally inferring O2(1(Delta) ) by measuring O2(3(Sigma) ) leads to better agreement between experiment and theory. These results strongly imply that if a COIL model is anchored to literature O2(1(Delta) ) measurements, caution needs to be applied when using the model for predicting performance.

Extraction efficiency of a 5-cm gain length supersonic chemical oxygen-iodine laser

Gain saturation and diffractive loss data have been collected on the Phillips Laboratorys VertiCOIL laser. These data have been applied to the COIL simplified saturation model to estimate the optical extraction efficiency of VertiCOIL.

Two-dimensional gain measurements in a chemical oxygen-iodine laser (COIL) device

The spatial distribution of gain has been investigated on the Research Assessment and Device Improvement Chemical Laser, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F equals 3 yields F equals 4 hyperfine levels of the (2P1/2) to (2P3/2) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle is about two times greater than measurements made on ReCOIL and compares favorably with measurements made on the Rotating Disk Generator (RotoCOIL) device. Gain distribution was investigated under three I2 flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena.