• Pieter Geiregat
  • Arjan J. Houtepen
  • Laxmi Kishore Sagar
  • Ivan Infante
  • Felipe Zapata
  • Valeriia Grigel
  • Guy Allan
  • Christophe Delerue
  • Dries Van Thourhout
  • Zeger Hens

Colloidal quantum dots (QDs) raise more and more interest as solution-processable and tunable optical gain materials. However, especially for infrared active QDs, optical gain remains inefficient. Since stimulated emission involves multifold degenerate band-edge states, population inversion can be attained only at high pump power and must compete with efficient multi-exciton recombination. Here, we show that mercury telluride (HgTe) QDs exhibit size-tunable stimulated emission throughout the near-infrared telecom window at thresholds unmatched by any QD studied before. We attribute this unique behaviour to surface-localized states in the bandgap that turn HgTe QDs into 4-level systems. The resulting long-lived population inversion induces amplified spontaneous emission under continuous-wave optical pumping at power levels compatible with solar irradiation and direct current electrical pumping. These results introduce an alternative approach for low-threshold QD-based gain media based on intentional trap states that paves the way for solution-processed infrared QD lasers and amplifiers.

Original languageEnglish
Pages (from-to)35-42
Number of pages8
JournalNature Materials
Issue number1
Publication statusPublished - 1 Jan 2018

ID: 41224561