An optically pumped molecular bromine laser

Molecular bromine has been observed to lase when optically pumped on individual vibration–rotation lines. With no dispersive elements in the laser cavity the output consists of several doublets, corresponding to P‐ and R‐branch transitions from the excited (B) state populated by the pump pulse to various vibrational levels of the ground state. The insertion of an intracavity prism causes a single doublet to lase, with a corresponding reduction in output power. In the current experiments the output wavelength was tunable from 550 nm in the green to 750 nm in the red for each transition pumped near 532 nm. The broadband efficiency was a few tenths of a percent, with the single‐line output efficiency one‐tenth of that. The theoretical gain at 10 torr and 300 K was estimated to be 0.05–0.40 per cm. This system offers a quasicontinuous tunable source of radiation ranging from the visible to 3.5 μm in the infrared.