Optical Resonance Transfer Laser (ORTL) Development

Abstract : This report describes an experimental program aimed at assessing the feasibility of using an intracavity ORTL system for HF laser mode control. The initial experiments utilized existing extracavity ORTL hardware to continue the investigation of ORTL kinetics. The most significant result of these initial experiments was the identification of SF6 as an alternative diluent to helium. The major part of the program was devoted to the fabrication and use of new intracavity ORTL hardware. Temporally stable spectrally controlled intracavity ORTL operation was demonstrated for the first time. The combined use of spectral control coatings in the chemical laser resonator and inlet temperature control of the ORTL medium resulted in ORTL outputs up to 152 watts and overall efficiencies of HF chemical laser radiation to HF ORTL output up to 38%. Detailed measurements of energy deposition in mirrors and in the ORTL medium, of temperature profiles, and of small signal gain utilizing helium and SF6 as ORTL diluents were made over a wide range of operational ORTL parameters. The simultaneous development of an intracavity ORTL model, including an HF chemical laser simulation, allowed comparison of theory and experiment. This resulted in the achievement of a good understanding of the physical processes which are important for efficient intracavity ORTL operation. The model code can now be used for the design of larger systems. Efficiencies of 85 to 90% should be attainable in large systems.