Distributed-feedback laser utilizing POPOP vapor

A distributed-feedback laser with an active medium in the form of a vapor of a complex organic compound was constructed and investigated. Lasing was observed in 1, 4-di[2-(5-phenyloxazolyl)]-benzene (POPOP) vapor when the concentration of a pentane impurity was 10¹⁹ – 4×10²¹ cm^–3 and the vapor was pumped with the second harmonic of a ruby laser or with a nitrogen laser (337 nm). A study was made of the dependence of the lasing wavelength on temperature and on the pentane pressure. The addition of pentane made it possible to achieve lasing at a repetition frequency up to 30 Hz without circulation of the active medium. A change in the density of the liquid active medium with temperature in the subcritical range made it possible to turn the emission wavelength of the POPOP distributed-feedback laser over a range of 42 nm.