Spectroscopy of 1.55μm 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 1.55μm. We demonstrate that a low density (≲100 μm−2) of QDs does not significantly degrade cavity quality factors as high as ≈3×104. 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.