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arXiv · 1112.2204

Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene

T. Li·L. Luo·M. Hupalo·J. Zhang·M. C. Tringides·J. Schmalian·J. Wang
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Abstract

We show that strongly photoexcited graphene monolayers with 35fs pulses quasi-instantaneously build up a broadband, inverted Dirac fermion population. Optical gain emerges and directly manifests itself via a negative optical conductivity for the first 200fs, where stimulated emission completely compensates absorption loss in the graphene layer. Our experiment-theory comparison with two distinct electron and hole chemical potentials reproduce absorption saturation and gain at 40fs, revealing, particularly, the evolution of the transient state from a hot classical gas to a dense quantum fluid with increasing the photoexcitation.

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T. Li, L. Luo, M. Hupalo, J. Zhang, M. C. Tringides, J. Schmalian, J. Wang. 2011-12-09. Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene. https://doi.org/10.1103/physrevlett.108.167401

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