New Journal of Physics (Jan 2018)

Controlling the gain contribution of background emitters in few-quantum-dot microlasers

  • F Gericke,
  • M Segnon,
  • M von Helversen,
  • C Hopfmann,
  • T Heindel,
  • C Schneider,
  • S Höfling,
  • M Kamp,
  • A Musiał,
  • X Porte,
  • C Gies,
  • S Reitzenstein

DOI
https://doi.org/10.1088/1367-2630/aaa477
Journal volume & issue
Vol. 20, no. 2
p. 023036

Abstract

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We provide experimental and theoretical insight into single-emitter lasing effects in a quantum dot (QD)-microlaser under controlled variation of background gain provided by off-resonant discrete gain centers. For that purpose, we apply an advanced two-color excitation concept where the background gain contribution of off-resonant QDs can be continuously tuned by precisely balancing the relative excitation power of two lasers emitting at different wavelengths. In this way, by selectively exciting a single resonant QD and off-resonant QDs, we identify distinct single-QD signatures in the lasing characteristics and distinguish between gain contributions of a single resonant emitter and a countable number of off-resonant background emitters to the optical output of the microlaser. Our work addresses the important question whether single-QD lasing is feasible in experimentally accessible systems and shows that, for the investigated microlaser, the single-QD gain needs to be supported by the background gain contribution of off-resonant QDs to reach the transition to lasing. Interestingly, while a single QD cannot drive the investigated micropillar into lasing, its relative contribution to the emission can be as high as 70% and it dominates the statistics of emitted photons in the intermediate excitation regime below threshold.

Keywords