Diffusion of excited state molecules in FIR- and CO2-lasers |
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Authors: | Reinhard Janker |
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Institution: | (1) Laboratories for High Frequency Technology, University Erlangen-Nürnberg, Cauerstr. 9, D-8520 Erlangen |
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Abstract: | Both standing waves in laser oscillators and spatially inhomogenous cross sections of laser beam and pumprate cause a non-uniform distribution of excited state molecules in longitudinal and transversal direction, respectively. This spatial hole burning however is smoothed by diffusion of the excited molecules. The effect of diffusion is investigated theoretically for an optically pumped far infrared laser as well as the corresponding CO2 pump laser. It is found, that the remaining spatial hole burning in the direction of wave propagation is negligible within CO2 lasers but not within FIR lasers. Concerning the transversal direction it can be shown that in the FIR laser diffusion takes no effect, whereas the transversal distribution of the excited molecules in the CO2 laser is significantly influenced by diffusion.FIR ring lasers avoid longitudinal spatial hole burning, which leads to the common assumption that they use the active medium more efficient than conventional standing wave lasers, hence delivering higher output powers. This expected advantage is levelled out to a great extent by diffusion. |
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Keywords: | FIR lasers ring lasers CO2 lasers diffusion |
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