Abstract
Many pyrromethene (PM) dyes have been shown to outperform established rhodamine dyes in terms of laser efficiency in the green-yellow spectral region, but their rapid photochemical degradation in commonly used ethanol or methanol solvents continues to limit its use in high average power liquid dye lasers. A comparative study on narrowband laser efficiency and photostability of commercially available PM567 and PM597 dyes, using nonpolar n-heptane and 1,4-dioxane and polar ethanol solvents, was carried out by a constructed pulsed dye laser, pumped by the second harmonic (532 nm) radiation of a -switched Nd:YAG laser. Interestingly, both nonpolar solvents showed a significantly higher laser photostability ( times) as well as peak efficiency () of these PM dyes in comparison to ethanol. The different photostability of the PM dyes was rationalized by determining their triplet-state spectra and capability to generate reactive singlet oxygen () by energy transfer to dissolved oxygen in these solvents using pulse radiolysis. Heptane is identified as a promising solvent for these PM dyes for use in high average power dye lasers, pumped by copper vapor lasers or diode-pumped solid-state green lasers.
© 2015 Optical Society of America
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