Smart Materials & Structures

Graphene has attracted considerable attention due to its massless and gapless energy spectrum. We designed and fabricated our original distributed-feedback dual-gate graphene-channel fi eld-eff ect transistor (DFB-DG-GFET). Th e DG-GFET structure serves carrier population inversion in the lateral p-i-n junctions under complementary dual-gate (Vg1,2) biased and forward drain-source (Vd) biased conditions, promoting spontaneous broadband incoherent THz light emission. The tooth-brash-shaped DG forms the DFB cavity having the fundamental mode at 4.96 THz, which can transcend the incoherent broadband LED to the single-mode lasing action. Th e GFET channel consists of a few layer (non-Bernal) highest-quality

epitaxial graphene, providing an intrinsic fi eld-eff ect mobility exceeding 100,000 cm2/Vs. Fourier-transform far-infrared spectroscopy revealed the THz emission spectra for the fabricated samples under population inversion conditions; one sample exhibited a 1-7.6-THz broadband, rather intense (~80 μW) amplifi ed spontaneous emission and the other sample did a weak (~0.1 μW) single mode lasing at 5.2 THz both at 100K. Introduction of the graphene plasmonics in vdW 2D heterostructures is a key to increase the operating temperature and radiation intensity. Asymmetric dual-grating-gate metasurface structures may promote plasmonic superradiance and/or plasmonic instabilities, giving rise to giant THz gain enhancement at plasmonic resonant frequencies. Further improvement will be given by a gated double-graphene-layer (G-DGL) nanocapacitor vdW 2D heterostructures. Exploitation of the graphene plasmonics in vdW 2D heterostructures will be the key to realize roomtemperature,intense THz lasing.