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DF: Fachverband Dielektrische Festkörper

DF 11: Poster

DF 11.3: Poster

Mittwoch, 9. März 2016, 18:00–20:00, Poster E

Effect of different excitation and collection geometries on the lasing threshold of PM597-doped WGM micro disk cavities — •Tobias Siegle, Marielle Bonenberger, Sarah Krämmer, Carolin Klusmann, and Heinz Kalt — Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany

The rotational symmetry and also the high quality factor of whispering gallery mode (WGM) micro resonators impedes free-space coupling of light to WGM cavities. Lasing modes in dye (pyrromethene 597)-doped WGM micro disks are excited through the free-space excitation of the active material within the cavity (fluorescence coupling). A more efficient excitation method is coupling to the evanescent field of a tapered fiber. Free-space and tapered fiber excitation geometries are compared regarding their effect on the lasing threshold: The localization of the pump energy by fiber excitation leads to a reduction of the lasing threshold by a factor of approximately one hundred as here only the WGM rim region of the cavity is excited.
In the free-space geometry light extraction from the cavity typically relies on impurities scattering the light towards the detector. Using the same tapered fiber for excitation and collection of light leads to a significant increase of the collection efficiency compared to the free-space geometry and does not depend on impurities.