Optically Defined Reconfigurable THz Metasurfaces using Graphene on Iron‐Doped Lithium Niobate

Abstract

Graphene plasmonic devices have been demonstrated to show great potential for reconfigurable metasurfaces due to the tuneable electronic charge transport properties of graphene in response to electrostatic gating. Iron‐doped lithium niobate is proposed as a platform for patterning‐free optically reconfigurable graphene metasurfaces in the THz spectral region. Under structured illumination, the lithium niobate undergoes charge migration in the bulk, where carriers migrate away from illuminated regions, forming spatially patterned charge distributions capable of electrostatic tuning of graphene. These charge distributions are stable in the dark, however, can be redefined by subsequent illumination. Through the use of numerical simulations, it is demonstrated that optically defined charge distributions in lithium niobate can tune locally the graphene Fermi level allowing for plasmonic resonances at THz frequencies.

Improving Linewidth and Extinction Ratio Performances of Lithium Niobate Ring Modulator Using Ring‐Pair Structure

“…[14][15][16][17][18][19][20][21] Importantly, the thin-film LN platform combines the excellent electro-optic properties of bulk LN with advantages of photonic films such as a high index contrast and tightly confined modes. [22][23][24][25][26][27][28][29][30][31][32][33][34][35] Although high-performance EOM systems with low drive voltage and ultrahigh bandwidth have been experimentally demonstrated using Mach-Zehnder interferometer (MZI) on thin-film LN, [27,30,36] the centimeter length of the MZI devices presents a big challenge for applications in large-scale integrated optical interconnection systems.To further reduce the footprint of a modulator, resonant ring modulators have been widely studied. Ring modulators are key components in short-range optical interconnects due to their low operating voltage, compact size, and compatibility with CMOS circuit drivers.…”