POPOP vapor laser with a 22% efficiency

Ether vapor at a pressure of 35 atm increased the equilibrium density of POPOP molecules in vapors by a factor of 100. When a mixture of POPOP vapor and ether was pumped by the third harmonic of a neodymium laser (355 nm), a lasing efficiency higher than 22% was obtained, this being comparable with the lasing efficiency of POPOP molecules in solutions. The low threshold intensity for excitation of laser action (I_th < 0.3 MW/cm²) when pumped by the fourth harmonic (266 nm) indicated that wide-band incoherent light sources can be used to pump POPOP vapor. For comparison, measurements were made of the lasing efficiency of lasers utilizing solutions of POPOP in dioxane (38%) and ether (50%). The fact that POPOP molecules retain their lasing properties at elevated temperatures also makes these potentially useful for solidstate lasers with porous matrices and for dye-aerosol lasers.