Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 18: Laser Development: Solid State Lasers II

Q 18.3: Vortrag

Dienstag, 9. März 2010, 14:30–14:45, F 128

Laser emission saturation in a small mode volume organic microcavity — •Robert Brückner, Martin Teich, Markas Sudzius, Hartmut Fröb, Vadim Lyssenko, and Karl Leo — Institut für Angewandte Photophysik, George-Bähr-Str. 1, 01069 Dresden, Germany

We investigate a high finesse organic microcavity (MC) (21 layer DBR of TiO₂ and SiO₂, λ/2-layer of Alq₃ doped with 2wt% DCM) under different pumping conditions using femtosecond pulses. We show that lasing saturation occurs in a small mode volume organic microcavity due to the limited number of excitable molecules per mode. On the one hand, a pumping wavelength of 400 nm is used to excite Alq₃ molecules with a subsequent transfer of the energy to DCM molecules via Förster-transfer. On the other hand, we pump the laser dye DCM directly to its absorption band (around 500 nm). In this case, a saturation of the output power is observed due to the finite number of DCM molecules in the mode volume. In contrast, the saturation of the output power occurs at much higher excitation levels if Alq₃ is pumped since the number of molecules is 50 times larger. A modified set of rate equations is applied to obtain a theoretical description of the lasing dynamics. These equations provide a basis to describe the occurence of saturation at high excitation levels in dependence of the excitation pulse width, the number of excited molecules in the mode volume, and the spontaneous emission factor β.