Seminar: “Organic VECSELs: Towards Low-Cost UV-Visible Lasers”, Sébastien Chénais
Thursday, February 2, 2012 / 3-4pm
Laser Physics Laboratory, University of Paris 13, 93430 Villetaneuse, France
Vertical External Cavity Surface Emitting Organic Lasers (VECSOLs) are the counterparts of VECSELs with organic solid-state gain materials, i.e. dye-doped polymer thin films or organic semiconductors. They combine the well-known properties of VECSELs (high conversion efficiency, excellent beam quality, power scaling capability, high versatility offered by the open cavity) with the key properties offered by organic thin films : low cost, ease of fabrication (by high-throughput processes such as spin coating, potentially ink-jet printing on large areas), broad emission spectra (typ. 100-nm wide) offering a high potential for wavelength tunability, easy chemical tuning (from near-UV to near-IR), and high gain. With a simple structure consisting of a plane highly-reflective mirror onto which a thin film of Rhodamine-640-doped PMMA layer was spin-cast and a concave output coupler closing the cavity, pumped by the second harmonic of a Nd:YAG laser (532 nm, 7 ns, 10 Hz), we achieved a record conversion efficiency of 60% with a diffraction-limited output at 620 nm. The open cavity allowed us to perform intracavity frequency doubling and obtaining a deep-UV laser continuously tunable from 309 to 322 nm, with 2% efficiency, in a very compact setup (1-cm long). Dynamical numerical simulations based on Statz-DeMars equations revealed that the very high gain cross sections (~10-16 cm²) combined to the short lifetime (~ns) of organics make the device performance highly dependent on cavity length and pump pulse duration. Photobleaching issues which are common to all organic solid-state lasers will be discussed.
For More Information:
Dr. Romain Gaume
gaume @ ucf. edu