Grating-graphene metamaterial as a platform for terahertz nonlinear photonics

Abstract

Nonlinear optics is an increasingly important field for scientific and technological applications, owing to its relevance and potential for optical and optoelectronic technologies. Currently, there is an active search for suitable nonlinear material systems with efficient conversion and small material footprint. Ideally, the material system should allow for chip-integration and room-temperature operation. Two-dimensional materials are highly interesting in this regard. Particularly promising is graphene, which has demonstrated an exceptionally large nonlinearity in the terahertz regime. Yet, the light-matter interaction length in two-dimensional materials is inherently minimal, thus limiting the overall nonlinear-optical conversion efficiency. Here we overcome this challenge using a metamaterial platform that combines graphene with a photonic grating structure providing field enhancement. We measure terahertz third-harmonic generation in this metamaterial and obtain an effective third-order nonlinear susceptibility with a magnitude as large as 3$\cdot$10${}^{-8}$m${}^2$/V${}^2$, or 21 esu, for a fundamental frequency of 0.7 THz. This nonlinearity is 50 times larger than what we obtain for graphene without grating. Such an enhancement corresponds to third-harmonic signal with an intensity that is three orders of magnitude larger due to the grating. Moreover, we demonstrate a field conversion efficiency for the third harmonic of up to $\sim$1% using a moderate field strength of $\sim$30 kV/cm. Finally we show that harmonics beyond the third are enhanced even more strongly, allowing us to observe signatures of up to the 9${}^{\mathrm{th}}$ harmonic. Grating-graphene metamaterials thus constitute an outstanding platform for commercially viable, CMOS compatible, room temperature, chip-integrated, THz nonlinear conversion applications.

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• Milliwatt terahertz harmonic generation from topological insulator metamaterials
• Terahertz signatures of ultrafast Dirac fermion relaxation at the surface of topological insulators at room temperature
• Recent advances in terahertz photonic technologies based on graphene and their applications
• Tailored nano-electronics and photonics with two-dimensional materials at terahertz frequencies
• Engineering THz-frequency light generation, detection and manipulation through graphene
• Hybrid Graphene-Plasmon Gratings
• High-harmonic generation enhancement with graphene heterostructures
• Observation of terahertz second harmonic generation from Dirac surface states in the topological insulator Bi${}_2$Se${}_3$
• Rigorous Signal Reconstruction in Terahertz Emission Spectroscopy
• Plasmon polariton assisted second-harmonic generation in graphene
• Highly efficient broadband THz upconversion with Dirac materials
• Ultrafast terahertz conductivity in epitaxial graphene nanoribbons: an interplay between photoexcited and secondary hot carriers
• Ultrafast electronic heat dissipation through surface-to-bulk Coulomb coupling in quantum materials
• Giant enhancement of terahertz high-harmonic generation by cavity engineering of a three-dimensional Dirac semimetal