Spectroscopy of 1.55 $\mu$m PbS Quantum Dots on Si Photonic Crystal Cavities with a Fiber Taper Waveguide

TL;DR

This study demonstrates a fiber taper waveguide technique to perform spectroscopy on PbS quantum dots on silicon photonic crystal cavities at 1.55 μm, enabling efficient excitation and collection of photoluminescence with minimal cavity degradation.

Contribution

The paper introduces a fiber taper waveguide method for probing PbS quantum dots on silicon photonic cavities, facilitating spectroscopy in the telecommunications band with high cavity quality factors.

Findings

Quantum dots do not significantly degrade cavity quality factors.

The fiber taper can excite QDs and collect cavity-filtered photoluminescence.

Reversible photodarkening and QD saturation observed.

Abstract

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 ($\lesssim 100 \mu$m$^{-2}$) of QDs does not significantly degrade cavity quality factors as high as $\approx3\times10^4$. 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 towards spectroscopy of single colloidal QDs in the telecommunications band.