Enhanced photoluminescence from germanium-based ring resonators

We report the enhancement of direct bandgap emission from germanium ring resonators based on silicon-on-insulator (SOI). As a consequence of their strong confinement, a record quality factor (Q) of 620 is obtained that is an order of magnitude higher than that previously characterized for crystalline germanium microcavities. We also describe a pump power dependency of Q due to bandedge shifts not previously reported for silicon-or germanium-based emitters. A decline in the relative peak to baseline intensities with lower Qs is attributed to the Purcell effect on account of the wavelength-scale dimensions and high index contrast of our samples. (C) 2008 American Institute of Physics.