The question of 'what is a laser' is closely related to that of what is laser threshold. We analyze possible definitions of laser threshold through the L-I curve and conclude that there is no consistent definition of a threshold when the spontaneous emission factor is large, as in the case of micro-and nano-lasers. All these definitions based on L-I curve are not consistent with the evolution of statistical properties of light output with pumping. Thus, we argue that the threshold definition based on L-I curve has to be abandoned for nanolasers, where the fraction of spontaneous emission into a lasing mode becomes quite large.

Original languageEnglish (US)
Article number6516933
JournalIEEE Journal on Selected Topics in Quantum Electronics
Issue number4
StatePublished - 2013


  • Correlation functions
  • laser threshold
  • nanolasers
  • spontaneous emission factor

ASJC Scopus subject areas

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


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