Efficiency of coaxial laser pumping systems

The efficiency of a coaxial optical pumping system of finite length is calculated theoretically allowing for multiple reemission of the radiation transmitted by the pump enclosure and absorbed by the lamp plasma. The efficiency of such a system is expressed in terms of the radiant flux emitted by the plasma, total and spectral energy efficiency of the lamp, and other parameters which can be determined experimentally when the active element and lamp plasma are separated by an arbitrary number of media. The expressions for the efficiency are used in calculations of a specific coaxial system which has been investigated experimentally. It is shown that the efficiency of such a system can be found correctly only if the reemission process is allowed for and that the maximum energy of a lamp in a pump enclosure may be considerably lower than the maximum energy outside an enclosure. The results can also be used in the design of pumping systems of different kinds.