Fiber-based cryogenic and time-resolved spectroscopy of PbS quantum dots

TL;DR

This paper introduces fiber-based cryogenic and time-resolved spectroscopy techniques for PbS quantum dots, enabling improved detection and understanding of their optical properties at low densities and various temperatures.

Contribution

It presents novel fiber taper waveguide methods for efficient photoluminescence extraction and temperature-dependent measurements of PbS quantum dots.

Findings

Photon emission increases at lower temperatures.

Excited-state lifetime extends from 58.9 ns to 657 ns as temperature decreases.

Successful measurements on quantum dots coupled to high-Q microdisks.

Abstract

PbS quantum dots are promising active emitters for use with high-quality Si nanophotonic devices in the telecommunications-band. Measurements of low quantum dot densities are limited both because of low fluorescence levels and the challenges of single photon detection at these wavelengths. Here, we report on methods using a fiber taper waveguide to efficiently extract PbS quantum dot photoluminescence. Temperature dependent ensemble measurements reveal an increase in emitted photons concomitant with an increase in excited-state lifetime from 58.9 ns at 293 K to 657 ns at 40 K. Measurements are also performed on quantum dots on high-$Q$ ($>10^5$) microdisks using cavity-resonant, pulsed excitation.