title: Saturation behaviour of colloidal PbSe quantum dot exciton emission                     coupled into silicon photonic circuits.
abstract: We report coupling of the excitonic photon emission from photoexcited PbSe colloidal quantum dots (QDs) into an optical circuit that was fabricated in a silicon-on-insulator wafer using a CMOS-compatible process. The coupling between excitons and sub-μm sized silicon channel waveguides was mediated by a photonic crystal microcavity. The intensity of the coupled light saturates rapidly with the optical excitation power. The saturation behaviour was quantitatively studied using an isolated photonic crystal cavity with PbSe QDs site-selectively located at the cavity mode antinode position. Saturation occurs when a few μW of continuous wave HeNe pump power excites the QDs with a Gaussian spot size of 2 μm. By comparing the results with a master equation analysis that rigorously accounts for the complex dielectric environment of the QD excitons, the saturation is attributed to ground state depletion due to a non-radiative exciton decay channel with a trap state lifetime ~ 3 μs.
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Foell
authors.forename: Ellen
authors.initials: E
authors.lastname: Schelew
authors.forename: Haijun
authors.initials: H
authors.lastname: Qiao
authors.forename: Keith A
authors.initials: KA
authors.lastname: Abel
authors.forename: Stephen
authors.initials: S
authors.lastname: Hughes
authors.forename: Frank C J M
authors.initials: FC
authors.lastname: van Veggel
authors.forename: Jeff F
authors.initials: JF
authors.lastname: Young
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods; D060733:Electromagnetic Radiation; D004867:Equipment Design; D006371:Helium / Q000737:chemistry; D007854:Lead / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning / Q000379:methods; D015233:Models, Statistical; D009356:Neon / Q000737:chemistry; D016011:Normal Distribution; D017785:Photons; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D012997:Solvents
chemical_list: D003102:Colloids; D018036:Selenium Compounds; D012997:Solvents; C088065:lead selenide; D006371:Helium; D007854:Lead; D009356:Neon; D012825:Silicon