Spectroscopy of 1.55 μm PbS quantum dots on Si photonic crystal cavities with a fiber taper waveguide

We use an optical fiber taper waveguide to probe PbS quantum dots (QDs) dried on Si photonic crystal cavities near 1.55 mu m. We demonstrate that a low density (<= 100 mu m(-2)) of QDs does not significantly degrade cavity quality factors as high as approximate to 3 x 10(4). We also show that the tapered fiber can be used to excite the QDs and collect the subsequent cavity-filtered photoluminescence, and present measurements of reversible photodarkening and QD saturation. This method represents an important step toward spectroscopy of single colloidal QDs in the telecommunications band. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3396988]