Alan I. Lampson

Experimental investigation of an optically pumped mid-infrared carbon monoxide laser

Results from a dual experimental/theoretical investigation of an optically pumped room-temperature carbon monoxide (CO) laser are discussed. Ro-vibrational transitions in the (2, 0) overtone of CO at 2.3 /spl mu/m were pumped with an optical parametric oscillator to generate lasing on (2, 1) band transitions near 4.7 /spl mu/m. During the build-up of the laser pulse, only rotational redistribution of the initial optically pumped population was observed in the resolved CO spectra. Calculations describing the CO laser pulse dynamics and collisional relaxation rates support this observation. The addition of helium and argon bath gases enhanced the rotational relaxation process. A pressure dependent loss mechanism that degrades optical efficiency has been identified and possible causes are discussed.

Experimental and theoretical investigation of a coaxial pumped photolytic atomic bromine laser

This paper describes the results from a combined experimental theoretical investigation of a coaxial pumped photolytic bromine laser. A 532-nm pump was used to photodissociate IBr and produce Br*(/sup 2/P/sub 1/2/) with subsequent lasing on the (/sup 2/P/sub 1/2/)/spl rarr/(/sup 2/P/sub 3/2/) transition. Experimental results are presented for output energy, mode buildup time and small-signal gain as a function of pump energy and mirror outcoupling fraction. A simplified rate equation model was developed to predict the laser performance parameters and shows good agreement with the laser output energy and small-signal gain.

Comparison of subsonic and supersonic mixing mechanisms for the chemical oxygen-iodine laser (COIL) using computational fluid dynamic (CFD) simulations

Simulation of chemical lasers such as the chemical oxygen-iodine laser (COIL) laser is of timely interest due to ongoing commercial and military development programs. Accurate models of the gas dynamics and chemistry within a COIL have been developed using Computational Fluid Dynamics (CFD) codes, matching data from experiments designed to probe these physics. This work details the use of these codes to investigate the supersonic injection of molecular I2 and atomic I into the supersonic region of the O2(1?) flow in the COIL, and compare these results with a simulation of sonic injection of I2 into the subsonic region of the O2(1?) flow. The performance of each of these injection mechanisms is characterized by the theoretical power extracted from a Fabry-Perot resonator model, which then serves as the primary basis for comparison. Additional quantities such as power available and chemical efficiency are used to compare and contrast the performance of each concept. Based on these comparisons, the supersonic-supersonic injection methods demonstrate a performance increase over the traditional subsonic methods, with supersonic injection of I atoms providing the greatest performance increase.

3-D Navier-Stokes Simulation of Chemical Laser Devices

Chemical lasers are complex devices that couple twophase chemistry, fluid dynamics, and optics to generate coherent radiation capable of projecting high energy fluxes very large distances at the speed of light. Such a capability is an obvious candidate for precision engagement of targets in multiple theaters of operation, as evidenced by development programs that are intended to advance chemical lasers from the laboratory to the weapon platform. Given the complexity of the interactions between the various physical processes, simulation of chemical lasers presents an obvious opportunity for the application of high performance computing to facilitate the understanding and optimization of these devices. The work presented here illustrates how high performance computing is used to achieve an increased understanding of the physics underlying chemical oxygen iodine lasers (COILs) and their operation. Computational Fluid Dynamics (CFD) for the chemically reacting COIL flowfield coupled to radiation transport models for the optical field are executed commiserate with achieving these goals.

Chemical oxygen-iodine laser (COIL) beam quality predictions using 3D Navier-Stokes (MINT) and wave optics (OCELOT) codes

This paper describes a series of analyses using the 3-d MINT Navier-Stokes and OCELOT wave optics codes to calculate beam quality in a COIL laser cavity. To make this analysis tractable, the problem was broken into two contributions to the medium quality; that associated with microscale disturbances primarily from the transverse iodine injectors, and that associated with the macroscale including boundary layers and shock-like effects. Results for both microscale and macroscale medium quality are presented for the baseline layer operating point in terms of single pass wavefront error. These results show that the microscale optical path difference effects are 1D in nature and of low spatial order. The COIL medium quality is shown to be dominated by macroscale effects; primarily pressure waves generated from flow/boundary layer interactions on the cavity shrouds.

Frequency-tunable optically pumped carbon monoxide laser

Single-line frequency-tunable lasing was observed in an optically pumped, repetitively pulsed, room-temperature CO laser for the first time. The R(0) and R(7) ro-vibrational transitions in the (2,0) overtone of CO at 2.3 /spl mu/m were optically pumped with a high-energy optical parametric oscillator. Single-line lasing was observed on (2,1) P(2)-P(17) transitions and R(0)-R(11) transitions (covering wavelengths within the range 4.6-4.9 /spl mu/m) when using a diffraction grating as the spectrally selective reflector of the laser resonator. The observed CO laser pulse lengths were /spl sim/10/sup -7/ s with peak power up to 10/sup 4/ W. The influence of CO pressure, the addition of buffer gas (He, Ar), Q-factor of the laser resonator, and the pump pulse energy on CO laser pulse temporal characteristics and output energy spectral distribution was studied experimentally.