Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene
| Title | Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene |
| Publication Type | Journal Article |
| Year of Publication | 2012 |
| Authors | Li T, Luo L, Hupalo M, Zhang J, Tringides MC, Schmalian J, Wang J |
| Journal Title | Physical Review Letters |
| Volume | 108 |
| Pages | 167401 |
| Date Published | 04 |
| Type of Article | Article |
| ISBN Number | 0031-9007 |
| Accession Number | WOS:000302854500007 |
| Keywords | epitaxial graphene, ultrafast |
| Abstract | We show that strongly photoexcited graphene monolayers with 35 fs pulses quasi-instantaneously build up a broadband, inverted Dirac fermion population. Optical gain emerges and directly manifests itself via a negative conductivity at the near-infrared region for the first 200 fs, 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 40 fs, revealing, particularly, the evolution of the transient state from a hot classical gas to a dense quantum fluid with increasing the photoexcitation. |
| URL | <Go to ISI>://WOS:000302854500007 |
| DOI | 10.1103/PhysRevLett.108.167401 |
| Alternate Journal | Phys. Rev. Lett. |
