The influence of the gain - Carrier density characteristic on Q-switching in quantum-dot lasers

Huw D. Summers, Paul Rees, Daniel R. Matthews, Gareth T. Edwards, Martyn R. Brown, Marta Cundin, Javier Dominguez, G. M. Lewis

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


A comparison is made between the Q-switched performance of both quantum dot and quantum well lasers operating in the 1-μm emission range. In contrast to the 2-D system, the quantum dot devices readily produce high-power pulses, but this is associated with significant pulse broadening such that the minimum pulsewidth is in excess of 1 ns. Comparison of the experimental results with a simple rate equation model shows that the Q-switching characteristics of the dot lasers are due to their operation close to the point of total inversion of the charge carrier populations. The resulting severe gain saturation, which drives the differential gain close to zero, significantly modifies the ratio of differential absorption to differential gain, which is known to govern the Q-switching characteristics of a laser diode. Measurements on the absorption properties of the dots show that there is no change in their absorption coefficient under a reverse bias, and correspondingly, there is minimal alteration of the Q-switch pulse parameters.

Original languageEnglish (US)
Pages (from-to)1222-1226
Number of pages5
JournalIEEE Journal on Selected Topics in Quantum Electronics
Issue number5
StatePublished - Sep 2007


  • Q-switched lasers
  • Quantum dots
  • Semiconductor lasers

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Atomic and Molecular Physics, and Optics


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