title: High laser efficiency and photostability of pyrromethene dyes mediated by nonpolar solvent.
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 Q-switched Nd:YAG laser. Interestingly, both nonpolar solvents showed a significantly higher laser photostability (∼100 times) as well as peak efficiency (∼5%) 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 (O21) 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.
authors.forename: Monika
authors.initials: M
authors.lastname: Gupta
authors.forename: Priyadarshini
authors.initials: P
authors.lastname: Kamble
authors.forename: M C
authors.initials: MC
authors.lastname: Rath
authors.forename: D B
authors.initials: DB
authors.lastname: Naik
authors.forename: Alok K
authors.initials: AK
authors.lastname: Ray