Whispering gallery modes in silicon nanocrystal coated microcavities

We present photoluminescence studies of silicon-nanocrystal (Si-NC) coated microcavities. The particular geometries studied are hollow fibers where there is a Si-NC coating in the inner surface and regular optical fibers and glass microspheres where the coating is on the outside Surface. The coatings were prepared using an inexpensive and straightforward solution-based process that yields a high-quality film. The measured photoluminescence spectra from the resonators show high Q-factor (between 1200 and 2800) resonant modes that correspond with the whispering gallery modes expected from the confinement geometries. The presence of these modes is also an indication that the emission of the Si-NCs is coupled to the cavity. The combination of Si-NCs and optical microcavities with strong confinement has promising potential for applications like sensing, optical communications and may be a possible route toward a Si-NC laser. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim