Proceedings Article | 9 May 2012
Proc. SPIE. 8433, Laser Sources and Applications
KEYWORDS: Thin films, Energy efficiency, Solid state lasers, Photodiodes, Laser resonators, Optical simulations, Laser damage threshold, Laser optics, Pulsed laser operation, Rhodamine
Organic lasers offer the promise to build compact, inexpensive, broadly tunable solid-state lasers in the visible range,
with potential applications in spectroscopy, bio/chemo sensing or short-haul data telecommunications. Among existing
laser architectures of optically-pumped organic lasers, external-cavity resonators enable the highest conversion
efficiencies, excellent beam quality, power scalability and versatility due to the open cavity. Recently, we reported on an
open-cavity laser architecture using a thin film of dye-doped polymer as the gain medium, named Vertical External
Cavity Surface-emitting Organic Laser (VECSOL). The very high gain of organics make these lasers highly efficient
even for macroscopic cavities, even though the pulse buildup time must be short enough to fit within the gain time
window defined by the pump pulse duration and the fluorescence lifetime.
In this paper we analyze the laser turn-on dynamics of organic VECSELs. A simple theoretical framework is presented,
based on the Statz-DeMars coupled rate equations. Simulations are compared to the experimental pulse shapes of the
pump and laser beams, recorded with the same fast photodiode. We observe that the laser pulse is both shifted and
broadened with respect to the 0.5-ns-long pump pulse when the cavity length is increased, together with a drop of
efficiency. Efficiency curves are presented, showing a higher threshold and lower slope efficiency when the cavity length
increases, which is well accounted by the model. Finally, an optimized VECSOL is presented, with a 25 ns-pulsewidth
pump source, enabling reaching conversion efficiencies up to 61%.
