0191-9067/81 /040367-15$02.00/0 Copyright ® 1981 SUNSAT Energy Council SOLAR-PUMPED ELECTRONIC-TO-VIBRATIONAL ENERGY TRANSFER LASERS W. L. HARRIES Old Dominion University Norfolk, Virginia 23508, USA J. W. WILSON NASA Langley Research Center Hampton, Virginia 23665, USA Abstract — The possibility of using solar-pumped lasers as solar energy converters is examined. The absorbing media considered are halogens or halogen compounds, which are dissociated to yield excited atoms, which then hand over energy to a molecular lasing medium. Estimates of the temperature effects for a Brj-COj-He system with He as the cooling gas are given. High temperatures can cause the lower energy levels of the CO2 laser transition to be filled. The inverted populations are calculated and lasing should be possible. However, the efficiency is less than 10 3. Examination of other halogen-molecular lasant combinations (where the rate coefficients are known) indicate efficiencies in all cases of less than 5 x 10~3. I. INTRODUCTION One concept for collecting solar energy is to use large solar collectors on orbiting space stations, which then transmit the energy as laser beams. If the solar energy could be converted directly into laser radiation, the inefficiencies in converting the energy through different transducers could be avoided. Gas lasers would be advantageous because they provide a uniform medium, structural problems are reduced, and the volume could be large. Here the concept of solar-pumped gas lasers used as energy converters is examined. The difficulties lie in the fact that the major fraction of the solar radiation lies in the longwave (visible) region of the spectrum with a peak at about 2 eV. An efficient absorber [1] must be broadband, [2] must absorb near the peak of the solar spectrum, and [3] the excited state must be at an energy level sufficiently great to yield reasonable quantum efficiency. The halogens can be dissociated at these energies, resulting in one atom being in an electronically excited state due to an electron spin flip. The excited levels are at a few tenths of an eV, comparable with the levels of molecular lasants. Only the halogens and halogen compounds are considered here as absorbers, although of course other materials may be feasible. Two possibilities are open once the energy has been absorbed: either the absorbing medium lases or it hands over the energy to a different medium. The case where the absorber and lasing medium are the same will be treated elsewhere. In view of the high efficiencies of CO2 lasers, a BR2-CO2-He laser is considered as a first example with the helium acting as a cooling medium. Recently Gordiets, Gudzenko and Panchenko (1) published a theoretical analysis
RkJQdWJsaXNoZXIy MTU5NjU0Mg==