Optically pumped mid-infrared laser action - in the monohaloacetylenes

Strong optically pumped laser action excited by a TEA carbon dioxide laser has been obtained from monofluoro-acetylene in the 560-610 cm-’ region with outputs of up to 25 mJ and superfluorescent operation readily achieved without optimisation. These result from excitation of a combination of the two bending modes v4+v5. Laser action was also obtained with 9 pm excitation of the v3 C-F stretch, on a difference band terminating in v4, with similar properties. Lasers of this type are rare. As well as being a potentially useful laser source in a region sparsely populated with good lasers, the results are of interest in the context of on going investigations of the spectroscopy of HCCF. Most, but not all lines are assigned. Very weak, erratic laser action was observed from chloroand bromo-acetylene.