Singular laser behavior of hemicyanine dyes: Unsurpassed efficiency and finely structured spectrum in the near-IR region

Abstract

In this paper we identify the origin of a novel and singular laser behavior of the hemicyanine dye LDS 722 transversally pumped at 532 nm. With lasing efficiencies as high as 43%, in spite of the fluorescence quantum yields being as low as 0.075, the laser spectra exhibit a finely structured spectral profile, with a periodic modulation with peak separation 0.4 nm, not related to mode selection due to spatial or spectral hole burning. The correlation of the LDS 722 lasing behavior as a function of both environmental properties (polarity, viscosity, protic character of the solvent) and pumping conditions (cavity configuration, pump geometry and energy) with its photophysical properties provides inklings to understand the physics responsible for the peculiar laser behavior in these rather complex dyes.