A high gain, low loss, and low-threshold spherical organic laser based on highly miscible excited-state intramolecular proton transfer dyes

Here, we report two types of excited-state intramolecular proton transfer dyes featuring exceptionally high miscibility with a polymer matrix (>50 wt%). Using these dyes, we assemble spherical laser oscillators and observe a significant reduction in the laser emission threshold at higher dye concentrations due to the enhanced optical gain as well as suppressed self-absorption and light scattering.