Efficient, two-photon pumped green upconverted cavity lasing in a new dye

Two-photon pumped green cavity lasing has been observed in a solution of a new dye in N,N-dimethyl formamide (DMF). The dye, 4-[N-(2-hydroxyethyl)-N-(methyl) amino phenyl]-4′-(6-hydroxyhexyl sulfonyl)stilbene, abbreviated as APSS, shows a strong two-photon absorption induced fluorescence when excited at 800 nm. The molecular two-photon absorption cross section was measured to be σ₂=1.5 × 10^-19 cm⁴/GW or σ′2=3.8 × 10^-47 cm⁴/photon/s, and is 1 to 2 orders of magnitude higher than Rhodamine 6G. The peak of the lasing spectrum was around 555 nm, and is to the best of our knowledge, the shortest wavelength obtained from a two-photon pumped dye laser. The conversion efficiency from the absorbed pump energy to the lasing output energy was as high as 2.8%. The absorption and the fluorescence spectra of the new dye, along with the spectral and temporal behavior of the two-photon pumped lasing output is presented.