Simultaneous ESR and laser action in ruby

The work to be described is aimed at the achievement of simultaneous microwave and optical maser action in ruby, as an extension of earlier work on a laser-pumped microwave maser. Such optical cascade pumping has some fundamental advantages compared to the case for which the optical and microwave maser action occur in separate crystals. A ruby laser rod (cooled to 90°K) has been incorporated into an open-sided X-band cavity, and observations have been made of the zero field ground state ESR during laser action. The laser output was monitored by a Fabry-Perot interferometer and consisted of one or two lines (depending on the optical pump power and the level of ESR saturation) corresponding to the²E(oE) → ± 1/2 and ± 3/2⁴A2transitions. For pump energies up to about twice threshold the changes which occurred in the ESR absorption during the sequence of flashlamp pumping, laser action, and fluorescent decay from the²E levels were consistent with the known laser and fluorescent characteristics. At higher pump energies, however, anomalous effects were observed in that sudden large changes in the ESR absorption occurred prior to the onset of laser oscillation. A description of the apparatus and possible interpretations of the results will be given.