Spectroscopy and laser characteristics of copper-vapor-laser pumped Pyrromethene-556 and Pyrromethene-567 dye solutions

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Abstract
We measured the basic optical properties of Pyrromethene-567 (P567) and Pyrromethene-556 (P556) dye solutions that are relevant to their application as dye lasers. The fluorescence spectra of methanol solutions show mirror images in relation to the absorption spectra, with Stokes shifts of 29.5 and 37.5 nm, respectively, for the two dyes. The central fluorescence peaks were at 546 and 535 nm, with widths of ∼40 and ∼50 nm (FWHM). The quantum yields were 97% ± 5% and 78% ± 5% for P567 and P556, respectively. Fluorescence lifetimes of 6.0 ± 0.2 ns were obtained for both dyes in methanol. Laser action, obtained by pumping with the green emission line (510.6 nm) from a copper-vapor laser, was measured in a Hänsch-type cavity. Tunability ranged from 531 to 590 nm for P567 and from 522 to 590 nm for P556. Lasing thresholds were ∼0.27 and ∼0.16 mJ/pulse, with 25% and 27% slope efficiencies for P567 and P556, respectively. Spectroscopy and lasing were studied in other solvents as well.