Small Signal Gain and Vibrational Relaxation for 13CO2*

Abstract

Because of the interest in CO2 isotopes for laser applications involving atmospheric propagation, we have determined the small signal gain for 13CO2 and compared the results with measurements for 12CO2 under identical pumping conditions. Previous work with low pressure cw lasers found that the small signal gain for 13CO2 was ≈60% of that for 12CO2.(1) Small signal gain measurements have not been reported for high pressures, but similar energies have been obtained from a TEA laser using both 13CO2 and 12CO2 gas mixes.(2) Absorption measurements indicate that the 00°1 - (10°0 + 02°0)I transition probability is higher for 13CO2,(3) which would result in higher small signal gain, if the inversion density is the same. Because of this conflicting information, it is difficult to design an amplifier operating with 13CO2. Therefore, we have measured the small signal gain for both 13CO2 and 12CO2 for the same pumping conditions.