2D-patterned graphene metasurfaces for efficient third harmonic generation at THz frequencies

Abstract

Graphene is an attractive two-dimensional material for nonlinear applications in the THz regime, since it possesses high third order nonlinearity and the ability to support tightly confined surface plasmons. Here, we study 2D-patterned graphene-patch metasurfaces for efficient third harmonic generation. The efficiency of the nonlinear process is enhanced by spectrally aligning the fundamental and third harmonic frequencies with resonances of the metasurface, leading to spatiotemporal energy confinement in both steps of excitation at ω and radiation at 3ω. This precise resonance alignment is enabled by the 2D-patterning; it is achieved by modifying the dispersion of the underlying plasmons and, thus, the spectral positions of the supported standing wave resonances. Efficiencies as high as −20dB (1%) for input intensity 0.1 MW/cm2 are achieved. Moreover, we verify that the efficiency does not deteriorate when finite-size metasurfaces are used in place of ideal periodic systems. Our results highlight the potential of graphene-based metasurfaces for nonlinear applications.

Topological Insulator Films for Terahertz Photonics

“…For comparison, we show also the results of measurements of p -doped graphene with a charge carrier concentration of about 10 13 cm −2 . Nowadays, graphene is the best material with the highest third harmonic conversion efficiency, reaching 1% and higher [ 47 , 48 , 49 ]. In our experiment, the highest field conversion efficiency in graphene is about 0.5%.…”

Recent advances in strongly resonant and gradient all-dielectric metasurfaces

“…(Note that e.g. graphene plasmons with a very short propagation wavelength can help avoid this, if so desired 74 .) Thus, the diffraction efficiency/directionality of the emitted THG wave can be controlled, e.g., by engineering the hybridization between Mie and qBIC modes as recently demonstrated 66 .…”

“…Through appropriate design of the asymmetric bars in a Si qBIC metasurface so that the resonance is lightspin-dependent, highly efficient THG with large circular dichroism was theoretically demonstrated. 73 Moreover, although metasurfaces operate in the non-diffractive regime at the fundamental frequency, the THG wave will be diffracted by the metasurface periodic lattice if the pitch does not remain subwavelength at the 3o frequency (note that, for instance, graphene plasmons with a very short propagation wavelength can help avoid this, if so desired 74 ). Thus, the diffraction efficiency/directionality of the emitted THG wave can be controlled, e.g., by engineering the hybridization between Mie and qBIC modes as recently demonstrated.…”

Enhanced terahertz frequency mixing in all-dielectric metamaterial with multiple surface plasmon polaritons resonances

“…The excitation of these highly localized SPPs in is accompanied by much stronger increase in the surface localized field, and the nonlinear optical processes are further strongly enhanced due to the dependence of the nonlinearity on the intensity. Therefore, the introduction of nonlinear graphene into metamaterials has been successfully used to enhance third harmonic generation (THG) [23][24][25][26][27][28], four-wave mixing (FWM) [29,30] and high harmonic generation (HHG) [31,32]. The graphene diffraction gratings were proposed to enhance THG by strong plasmonic resonances at fundamental frequency and third-harmonic [24].…”