Spectroscopic study on ultrafast carrier dynamics and terahertz amplified stimulated emission in optically pumped graphene

Taiichi Otsuji, Stephane Boubanga-Tombet, Akira Satou, Maki Suemitsu, Victor Ryzhii

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz (THz) stimulated emission in optically pumped graphene. The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range, which may lead to the development of new types of THz lasers. First, the non-equilibrium carrier relaxation/ recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carrier-carrier and carrier-phonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature, pumping photon energy/intensity, and carrier relaxation rates. Second, we conduct time-domain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field. Two different types of samples are prepared for the measurement; one is an exfoliated monolayer graphene on SiO2/Si substrate and the other is a heteroepitaxially grown non-Bernal stacked multilayer graphene on a 3C-SiC/Si epi-wafer.

Original languageEnglish
Pages (from-to)825-838
Number of pages14
JournalJournal of Infrared, Millimeter, and Terahertz Waves
Issue number8
Publication statusPublished - 2012 Aug


  • Graphene
  • Population inversion
  • Stimulated emission
  • Terahertz
  • Ultrafast carrier dynamics

ASJC Scopus subject areas

  • Radiation
  • Instrumentation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Spectroscopic study on ultrafast carrier dynamics and terahertz amplified stimulated emission in optically pumped graphene'. Together they form a unique fingerprint.

Cite this