High Power Chemical Oxygen Iodine Research Articles

Unstable resonators of high-power chemical oxygen—iodine lasers

Configurations of unstable resonators are considered depending on the basic parameters of a high-power chemical oxygen—iodine laser and the design of an unstable resonator is proposed which provides the compensation of the inhomogeneity of the small-signal gain downstream of the active medium, a high energy efficiency, and stability to intracavity aberrations. The optical scheme of this resonator is presented and its properties are analysed by simulating numerically the kinetics of the active medium and resonator itself in the diffraction approximation.

Synchronization of dual-line lasing and subsequent gigahertz modulation of iodine lasers through mode locking

Dual hyperfine line lasing of a Zeeman-tuned photolytic iodine laser resulting in 14-GHz modulated laser radiation was studied experimentally and theoretically as a function of the applied magnetic field. Synchronization of the phases of the two hyperfine lines necessary for optimum gigahertz modulation was achieved by mode locking. The resulting pulse durations of 740 ps were shorter than those previously observed without a magnetic field. Short pulses, together with the possibility of scaling the results to high-power chemical-oxygen iodine lasers, make this concept attractive for a laser-driven ultrawideband microwave source.

Scaling laws for thick-section cutting with a chemical oxygen–iodine laser

Almost all laser-assisted materials processing involves melting, vaporization and plasma formation which affect the utilization of laser energy for materials processing. To account for the effect of these phases, an effective absorptivity is defined, and a simple mathematical model is developed for the cutting of thick-section stainless steel using a high power chemical oxygen—iodine laser (COIL). The model is based on an overall energy balance, and it relates the cutting depth with various process parameters that can be used to predictively scale the laser materials processing performance to very thick sections. The effects of various process parameters such as laser power, spot size, cutting speed and cutting gas velocity on the cutting depth are discussed. The results of the mathematical model are compared with experimental data. Such a comparison provides a means of determining the effective absorptivity during laser materials processing.

Heuristic method for evaluating COIL performance

A heuristic methodology is described that was developed to evaluate the chemical efficiency of high-power chemical oxygen iodine laser (COIL) devices and its application to the specific evaluation of the U.S. Air Force Phillips Laboratory's RotoCOIL laser. A heuristic equation that forms the basis of this methodology and describes the COIL energy flow, energy losses, and power extraction using measured data, code results, and empirical relations is presented. Using this equation and bounding values for some of its terms, it is shown that for the RotoCOIL performance data the experimentally measured average O 2 ( 1 Δ) yield of 0.40 is nearly 38% below that which would be consistent with the measured extraction power. By relating terms of the heuristic equation to performance of individual components of the COIL system, it is concluded that nearly 50% of the efficiency loss for the RotoCOIL laser derives from oxygen generator and delivery losses, whereas 15% is from nozzle inefficiencies and 11% from resonator losses.

Theoretical and experimental studies of thick-section cutting with a chemical oxygen–iodine laser (COIL)

A simple mathematical model of thick-section stainless steel cutting with a high power chemical oxygen–iodine laser (COIL) is presented and compared with experimental results obtained with a 10-kilowatt COIL at the U.S. Air Force's Phillips Laboratory. This model uses a lumped-parameter technique to relate the cutting kerf depth with various process parameters and can be used to predict scaled laser materials processing performance to very thick sections. The model is similar to an empirical model developed by researchers in Japan, but includes predictive capabilities for thick metal cutting at very low velocities. The effects of various process parameters such as laser power, spot size and dimensions, and processing speed in the cutting depth are discussed and demonstrated. Finally, the ramifications of this model on thick-section processing of metals are presented, with emphasis on potential applications of COIL to high-speed, thick stainless steel cutting.

Effect of the Gas Temperature of a High-Power Chemical Oxygen-Iodine Laser on Calculated Small Signal Gain and Output Power

Rate equations describing the lasing kinetics of a high-power chemical oxygen-iodine laser were solved, taking into account the effect of gas temperature. The temperature rise resulting from deactivations was calculated at each computation step along the flow, with the temperature dependence of rate constants and of the heat capacitance of the total gas taken into account. It has been shown that the inclusion of the temperature effect has a significant influence on the calculated laser gain and laser output. The results of the present calculation verify the observation of surprisingly high gas temperature in the optical resonator in a previous experiment and indicate that the gas temperature of a subsonic, 1 kW-class chemical oxygen-iodine laser can easily be over 1000° C in the optical resonator unless a buffer gas is used to increase the heat capacitance.