Theory of low power ultra-broadband terahertz sideband generation in bi-layer graphene

Abstract

In a semiconductor illuminated by a strong terahertz field, optically excited electron-hole pairs can recombine to emit light in a broad frequency comb evenly spaced by twice the terahertz frequency. Such high-order terahertz sideband generation is of interest both as an example of extreme nonlinear optics and also as a method for ultrafast electro-optical modulation. So far, this phenomenon has only been observed with large field strengths (~10 kVcm-1), an obstacle for technological applications. Here we predict that bi-layer graphene generates high-order sidebands at much weaker terahertz fields. We find that a terahertz field of strength 1 kVcm-1 can produce a high-sideband spectrum of about 30 THz, 100 times broader than in GaAs. The sidebands are generated despite the absence of classical collisions, with the quantum coherence of the electron-hole pairs enabling recombination. These remarkable features lower the barrier to desktop electro-optical modulation at terahertz frequencies, facilitating ultrafast optical communications.

Updated to journal version with new title and expanded supplementary information. 18 Pages, 3 figures (with supplementary information 17 Pages, 3 figures)

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Cited by in corpus (7)

• Introduction to theory of high-harmonic generation in solids: tutorial
• Expanded view of electron-hole recollisions in solid-state high-order harmonic generation: Full-Brillouin-zone tunneling and imperfect recollisions
• High field response of gated graphene at THz frequencies
• Nonlinear optical conductivity of a generic two band systems, with application to doped and gapped graphene
• An explicit formula for high-order sideband polarization by extreme tailoring of Feynman path integrals
• Mechanism and modulation of terahertz generation from a semimetal - graphite
• Terahertz modulated optical sideband generation in graphene