Abstact-Terahertz emission from multiple-microcavity exciton-polariton lasers

S. Huppert, O. Lafont, E. Baudin, J. Tignon, and R. Ferreira

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.241302

Terahertz emission between exciton-polariton branches in semiconductor microcavities is expected to be strongly stimulated in the polariton laser regime due to the high density of particles in the lower state (final-state stimulation effect). However, nonradiative scattering processes depopulate the upper state and greatly hinder the efficiency of such terahertz sources. In this work, we suggest a scheme using multiple microcavities and exploiting the transition between two interband polariton branches located below the exciton level. We compare the nonradiative processes loss rates in single and double cavity devices and we show that a dramatic reduction can be achieved in the latter, enhancing the efficiency of the terahertz emission.

DOI: http://dx.doi.org/10.1103/PhysRevB.90.241302

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• Published 8 December 2014
• Received 9 September 2014
• Revised 6 November 2014

©2014 American Physical Society

Abstract-Room temperature broadband coherent terahertz emission induced by dynamical photon drag in graphene

J. Maysonnave, S. Huppert, F. Wang, S. Maero, C. Berger, W. de Heer, T.B. Norris, L.A. De Vaulchier, S. Dhillon, J. Tignon, R. Ferreira, J. Mangene

http://arxiv.org/abs/1405.6361

Nonlinear couplings between photons and electrons in new materials give rise to a wealth of interesting nonlinear phenomena. This includes frequency mixing, optical rectification or nonlinear current generation, which are of particular interest for generating radiation in spectral regions that are difficult to access, such as the terahertz gap. Owing to its specific linear dispersion and high electron mobility at room temperature, graphene is particularly attractive for realizing strong nonlinear effects. However, since graphene is a centrosymmetric material, second-order nonlinearities a priori cancel, which imposes to rely on less attractive third-order nonlinearities. It was nevertheless recently demonstrated that dc-second-order nonlinear currents as well as ultrafast ac-currents can be generated in graphene under optical excitation. The asymmetry is introduced by the excitation at oblique incidence, resulting in the transfer of photon momentum to the electron system, known as the photon drag effect. Here, we show broadband coherent terahertz emission, ranging from about 0.1-4 THz, in epitaxial graphene under femtosecond optical excitation, induced by a dynamical photon drag current. We demonstrate that, in contrast to most optical processes in graphene, the next-nearest-neighbor couplings as well as the distinct electron-hole dynamics are of paramount importance in this effect. Our results indicate that dynamical photon drag effect can provide emission up to 60 THz opening new routes for the generation of ultra-broadband terahertz pulses at room temperature.