Two-photon-pumped cavity lasing in a dye-solution-filled hollow-fiber system

Two-photon-pumped cavity lasing has been achieved in a dye-solution-filled hollow-fiber configuration that provides both a longer gain length and a higher local pump intensity. The gain medium is a solution of the new dye 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl]-4¢-(6-hydroxyhexyl sulfonyl)stilbene in dimethyl sulfoxide, which shows a strong two-photon-absorption-induced f luorescence when excited with near-infrared radiation. When the system is pumped with 800-nm 5-ns laser pulses, frequency-upconverted cavity lasing can be observed with a peak lasing wavelength near 565 nm and a 2 3.5-ns pulse duration. One of the major advantages of using a hollow-fiber geometry is the low two-photon pump threshold, which was measured to be as low as 20 30 mJ for a 15-cm-long hollow-fiber sample of 100-mm internal diameter. The conversion efficiency from the absorbed pump energy to the upconverted lasing output was 2.3%.